Progress 10/01/10 to 06/30/13

Outputs
Target Audience: Target audience is primarily growers and extension agents focuses on California tree-crop specialty agricultural sectors. Olive oil producers and select consumer educators are secondary target audiences Changes/Problems: Major change in approach is that PI is retired and project is complete What opportunities for training and professional development has the project provided? Presentations to Farm Advisor training classes. Presentations to county meetings organized by extension advisors for olive, almond, walnut and tree-fruit grower groups How have the results been disseminated to communities of interest? Research reports to multiple California industry research boards and commissions. Olive research results were presented at the Olive Biotech Conference held in Greece. The conference comprised an international professional research audience. Results relevant to olive oil producers in California were presented to agricultural professional audiences at short courses sponsored by the UC Davis Olive Center covering aspects of olive orchard management and on olive production practices. As co-chair of the UC Davis Olive Center I attended several meetings focused on interactions with olive industry leaders to review research results, and to coordinate Olive Center research and outreach activities with industry interests and priorities. I attended meetings of the Olive workgroup comprising University of California faculty and researchers, UC Cooperative Extension Advisors and Specialists and selected industry leaders and consultants. I had regular contact with University Cooperative Extension Advisors whose charge includes olive and olive oil production systems management What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Research on pollination and pollen compatibility relationships in super high-density olive orchards has been completed. Recent years have seen a revival of olive production in California following years of decline. The impetus for this renewed interest is twofold: First, there is the development of a solid and growing market for California olive oil, and second, growers have rapidly adapted new, highly mechanized planting systems. These innovations are based on cultivars new to California, where the olive industry was nearly exclusively based on ‘Manzanillo’ and ‘Mission’ grown in standard density orchards and managed using labor-intensive manual inputs. Previously my colleagues and I had demonstrated the pollination compatibility relationships for the traditional California cultivars. With the widespread plantings of the new (to California’s industry) cultivars, ‘Koroneki,’ ‘Arbequina’ and ‘Arbasano’ which are well adapted to these new production systems it has become necessary to determine cross compatibility relationships for these cultivars. The results of this research will certainly be of value to California’s oil olive producers much as our previous work was for the table olive producers. The results for table olive cultivars show that there is a strong relationship between temperature during bloom and expression of incompatibility such that the table olive cvs. behave as self-compatible in the cooler northern Sacramento Valley but as self-incompatible in the hotter southern San Joaquin Valley. With anticipated increases in temperature certain to occur in the coming years, these temperature-dependent aspects of reproductive biology will take on greater import. Other results include temperature-dependent aspects of flower abortion and fruit set in prune orchards. These results strongly suggest that new, high-temperature tolerant prune varieties are needed if California prune production will be able to continue under projected increased temperature scenarios.

Publications

Progress 01/01/12 to 12/31/12

Outputs
OUTPUTS: Olive research results were presented at the Olive Biotech Conference held in Greece. The conference comprised an international professional research audience. Results relevant to olive oil producers in California were presented to agricultural professional audiences at short courses sponsored by the UC Davis Olive Center covering aspects of olive orchard management and on olive production practices. As co-chair of the UC Davis Olive Center I attended several meetings focused on interactions with olive industry leaders to review research results, and to coordinate Olive Center research and outreach activities with industry interests and priorities. I attended meetings of the Olive workgroup comprising University of California faculty and researchers, UC Cooperative Extension Advisors and Specialists and selected industry leaders and consultants. I have regular contact with University Cooperative Extension Advisors whose charge includes olive and olive oil production systems management. PARTICIPANTS: Partner organizations include the California Olive Oil Council and the California Olive Commission. Training and professional development was offered to both of these groups through short courses offered by the UC Davis Olive Center. TARGET AUDIENCES: Target organizations include the California Olive Oil Council and the California Olive Commission. Training. The UC Davis Olive Center work targets growers, producers and consumers of California olive oil directly through courses and outreach efforts and indirectly through agencies such as the COOC, COC and UCCE. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Research continues on pollination and pollen compatibility relationships in super high-density olive orchards has been initiated. Recent years have seen a revival of olive production in California following years of decline. The impetus for this renewed interest is twofold: First, there is the development of a solid and growing market for California olive oil, and second, growers have rapidly adapted new, highly mechanized planting systems. These innovations are based on cultivars new to California, where the olive industry was nearly exclusively based on 'Manzanillo' and 'Mission' grown in standard density orchards and managed using labor-intensive manual inputs. Previously my colleagues and I had demonstrated the pollination compatibility relationships for the traditional California cultivars. With the widespread plantings of the new (to California's industry) cultivars, 'Koroneki,' 'Arbequina' and 'Arbasano' which are well adapted to these new production systems it has become necessary to determine cross compatibility relationships for these cultivars. The results of this research will certainly be of value to California's oil olive producers much as our previous work was for the table olive producers. The results for table olive cultivars show that there is a strong relationship between temperature during bloom and expression of incompatibility such that the table olive cvs. behave as self-compatible in the cooler northern Sacramento Valley but as self-incompatible in the hotter southern San Joaquin Valley. With anticipated increases in temperature certain to occur in the coming years, these temperature-dependent aspects of reproductive biology will take on greater import. Other results include temperature dependent aspects of flower abortion and fruit set in prune orchards. These results strongly suggest that new, high temperature tolerant prune varieties are needed if California prune production will be able to continue under projected increased temperature scenarios.

Publications

• No publications reported this period

Progress 01/01/11 to 12/31/11

Outputs
OUTPUTS: Olive research results were presented at the Olive Biotech 2011 meeting in Chania Crete. Results relevant to producers were also presented to agricultural professional audiences at short courses sponsored by the UC Davis Olive Center covering aspects of olive orchard management and on olive production practices. As co-chair of the UC Davis Olive Center I attended several meetings focused on interactions with olive industry leaders to review research results, and to coordinate Olive Center research and outreach activities with industry interests and priorities. I attended meetings of the Olive workgroup comprising University of California faculty and researchers, UC Cooperative Extension Advisors and Specialists and selected industry leaders and consultants. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
New research on pollination and pollen compatibility relationships in super high-density olive orchards has been initiated. Recent years have seen a revival of olive production in California following years of decline. The impetus for this renewed interest is twofold: First, there is the development of a solid and growing market for California olive oil, and second, growers have rapidly adapted new, highly mechanized planting systems. These innovations are based on cultivars new to California, where the olive industry was nearly exclusively based on 'Manzanillo' and 'Mission' grown in standard density orchards and managed using labor-intensive manual inputs. Previously my colleagues and I had demonstrated the pollination compatibility relationships for the traditional California cultivars. With the widespread plantings of the new (to California's industry) cultivars, 'Koroneki,' 'Arbequina' and 'Arbasano' which are well adapted to these new production systems it has become necessary to determine cross compatibility relationships for these cultivars. The results of this research will certainly be of value to California's oil olive producers much as our previous work was for the table olive producers. The results for table olive cultivars show that there is a strong relationship between temperature during bloom and expression of incompatibility such that the table olive cvs. behave as self-compatible in the cooler northern Sacramento Valley but as self-incompatible in the hotter southern San Joaquin Valley. With anticipated increases in temperature certain to occur in the coming years, these temperature-dependent aspects of reproductive biology will take on greater import. Other results include temperature-dependent aspects of flower abortion and fruit set in prune orchards. These results strongly suggest that new, high-temperature tolerant prune varieties are needed if California prune production will be able to continue under projected increased temperature scenarios.

Publications

• No publications reported this period

Progress 01/01/10 to 12/31/10

Outputs
OUTPUTS: Results or our olive research were presented at the International Symposium on Irrigation and Olive Oil Quality in Israel. Results relevant to producers were also presented to agricultural professional audiences at short courses sponsored by the UC Davis Olive Center: one on Super High Density Olive Orchard Management and one on Olive Production. As co-chair of the UC Davis Olive Center attended several meetings focused on interactions with olive industry leaders to review research results and to coordinate Olive Center research and outreach activities with industry interests and priorities. I attended meetings of the Olive workgroup comprising University of California faculty and researchers, UC Cooperative Extension Advisors and Specialists and selected industry leaders and consultants. PARTICIPANTS: Partner organizations include the California Olive Oil Council and the California Olive Commission. Training and professional development was offered to both of these groups through short courses offered by the UC Davis Olive Center. TARGET AUDIENCES: Target audience for olive outreach and research are California olive growers and olive oil producers PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Recent research in olive, walnut and prune focus on the biological bases for various production problems in these industries. Our work on olive cultivar genotyping has informed the academic and industry communities on the identity of olive germplasm resources contained in collections at Davis, Santa Barbara and Arizona. A useful outcome has been to clarify likely errors in the identification of germplasm in the local collections. This work has also facilitated our analysis of historical olive plantings at the California Channel Islands National Park with insights related to invasive olive genotypes on Santa Cruz Island. Our work on irrigation in olive orchards for oil production has been widely adopted by the California olive oil industry. We showed that olive oil yield and olive oil quality both are optimal at deficit irrigation levels. Our work on walnut pistillate flower abortion has been widely adopted as a management technique in the California walnut industry. Growers of vulnerable cultivars (especially -Serr-) now regularly treat their orchards with ethylene inhibitors during peak pistillate bloom to minimize losses due to pistillate flower abortion. Our results on temperature effects on prune pollination have provoked extensive discussion on the future of several tree-crop species in California in the face of looming climate change.

Publications

• A. Koehmstedt, M. K. Aradhya, D. Soleri, J. Smith, V. Polito. 2010. Molecular characterization of genetic diversity, structure, and differentiation in the olive (Olea europaea L.) germplasm collection of the United States Department of Agriculture. Genetic Resources and Crop Evolution. http://dx.doi.org/10.1007/s10722-010-9595-z
• Cuevas, J, V. Pinillos, V.S. Polito. 2009. Effective pollination period for -Manzanillo- and -Picual- olive trees. J. Horticultural Science and Biotechnology. 84: 370-374.
• M.T. DeCeault and V.S. Polito. 2010. High Temperatures during Bloom Can Inhibit Pollen Germination and Tube Growth, and Adversely Affect Fruit Set in the Prunus domestica Cultvars -Improved French- and -Muir Beauty-. Acta Horticulturae.
• D. Soleri, A. Koehmstedt, M. K. Aradhya, V. Polito, K. Pinney. 2010. Comparing the historic olive trees (Olea europaea L.) of Santa Cruz Island with contemporaneous trees in the Santa Barbara, CA area: a case study of diversity and structure in an introduced agricultural species conserved in situ. Genetic Resources and Crop Evolution. 57:973-984.

Progress 01/01/09 to 12/31/09

Outputs
OUTPUTS: Outputs comprise reports and presentations given to various audiences. Results or our olive research were presented at two international symposia: International Symposium on Olive Growing, International Horticultural Society in Portugal and the International Symposium on Irrigation and Olive Oil Quality in Israel. Results relevant to producers were also presented to agricultural professional audiences at short courses sponsored by the UC Davis Olive Center and workgroups comprising olive researchers and county advisors. I attended several meetings organized by the UC Davis Olive Center focused on interactions with olive industry leaders to review research results. Results on olive oil quality were presented at the joint UC Davis - Culinary Institute of America Conference on Beyond Extra Virgin which had as its primary audience large and small scale producers of California olive oil. Results of our prune pollination results were presented at the annual research meeting of the California Dried Plum Board. PARTICIPANTS: Collaborating institutions on this project include the UC Davis Olive Center which provided a focus for outreach and dissemination of results, the USDA National Clonal Germplasm Repository at Davis, including staff scientists and laboratory facilities, UC Santa Barbara Departments of Environmental Sciences and Geography, and the University of Cordoba (Spain) for assistance with cultivar identification. Collaborating individuals include Dr. Daniela Solari, UC Santa Barbara, Dr. Malli Aradhaya, USDA National Clonal Germplasm Repository Davis. TARGET AUDIENCES: There are multiple target audiences for this project. These include the professional research scientists working on olive oil production, olive cultivar identification, stone fruit pollination, and walnut reproductive biology. A second audience comprises California producers of olive oil, prunes and walnuts who are kept informed of our research results and have adopted them in standard management practices. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Our work on irrigation in olive orchards for oil production has been widely adopted by the California olive oil industry. We showed that olive oil yield and olive oil quality both are optimal at deficit irrigation levels. Our work on olive cultivar genotyping has informed the academic and industry communities on the identity of olive germplasm in local collections in the western US: Davis, Santa Barbara and Arizona. A useful outcome has been to clarify likely errors in the identification of germplasm in the local collections. Our work on walnut pistillate flower abortion has been widely adopted as a management technique in the California walnut industry. Growers of vulnerable cultivars (especially 'Serr') now regularly treat their orchards with ethylene inhibitors during peak pistillate bloom to minimize losses due to pistillate flower abortion. Our results on temperature effects on prune pollination have provoked extensive discussion on the future of several tree-crop species in California in the face of looming climate change.

Publications

• No publications reported this period

Progress 01/01/08 to 12/31/08

Outputs
OUTPUTS: Research is conducted on tree-fruit and tree-nut species with emphasis on Mediterranean climate-zone species grown in California. Our primary objectives involve investigations of aspects of reproductive biology that limit or constrain efficient crop production. Secondary objectives are to expand the scientific database on the fundamental process of reproductive biology in tree-crop species. Specific objectives are to 1) investigate field treatments of ethylene-inhibitors and suppressors of ethylene-action to reduce pistillate flower abortion in walnut; 2) investigate field treatments of ethylene-inhibitors and suppressors of ethylene-action to extend the effective pollination period of almond by extending the period of ovule viability; 3) investigate genetic diversity of olive cultivars of California and the world, historic olive germplasm of the California missions, invasive and feral populations of olives in wildlands of California channel islands, and non-pollinating fruitless olives grown for landscape trees in the arid southwest; 4) determine temperature effects on successful pollination, fertilization and fruit set in prune. Recent years have seen higher than normal temperatures during prune bloom in California. This has been correlated with exceptionally poor fruit set raising the question of the possible negative impacts of the high temperature conditions on set. We have shown that temperatures in excess of approximately 78F can disrupt pollen tube growth sufficiently to preclude fruit set in prune. Our approach to the prune fruit set problem has been to determine temperature pararmeters associated with each of the components of the effective pollination period: pollen germination and stigma receptivity, pollen tube growth in viable styles, ovule viability and successful fertilization.. For analysis of effective pollination period, ovule viability will be determined using aniline-blue staining with fluorescence microscopy of dissected ovules. Ovules of Prunus species present positive aniline-blue fluorescence, diagnostic for callose production, at the chalza as they become senescent. Pollen germination and tube growth will be studied in vitro under controlled temperature conditions and in vivo in trees subjected to localized temperature manipulations. Successful completion of objectives 1 and 2 will lead to new management tools to enhance production efficiencies in California walnut and almond orchards. Successful completion of objective 3 will establish a genetic database of olive germplasm for use in cultivar identification, population genetics of feral and invasive populations, and certification of pollenless cultivars for jurisdictions where only pollenless olive trees are permitted in landscape situations. Successful completion of objective 4 will suggest future limitations on the range of prune production in the face of warmer temperatures associated with global climate change. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
We have been conducting research and experiments in three areas. The first involves fruit set in walnut (Juglans regia), particularly walnut cultivars most severely affected by pistillate flower abortion (PFA). The experimental work on this project was concluded during the time period covered here. Field experiments using ethylene-inhibiting growth-regulator compounds aminovinylglycine and 1-MCP were continued during this reporting period. Our most recent experiments were designed to determine carry-over effects of multiple year applications with the primary objective of determining if the enhanced set attributable to reduced PFA in Serr walnut will adversely affect subsequent yields. Our second research area involves determining temperature affects on prune (Prunus domestica) fruit set. Experiments were conducted in vitro and in vivo. In vitro experiments were conducted using a temperature gradient system that creates ten temperature regimes. In vivo experiments were done with trees enclosed in temporary enclosures containing a greenhouse heater to create multiple temperature regimes. Results are modeled to determine high-temperature thresholds. We are approaching completion of a formal model to predict Serr walnut bloom overlap. Our intention is to continue to validate our results in Spring 2009. If the model remains robust with this final year's validation we expect to have it posted as an interactive web page for growers to use. Outcomes for our research activities involve changes in knowledge and changes in actions. Our results on prune responses to high temperatures during bloom tend to validate the recent observations and inferences regarding set. In years of high temperatures during prune bloom, set has been extremely poor. Three of the past four years have experienced such conditions. We have identified abrupt declines in pollen tube viability at threshold temperatures near the maxima observed in these years. With the looming specter of global climate changes suggesting that this may not be an isolated set of events, results such as ours may indicate that a shift in the range in prune production is imminent. We have preliminary evidence to suggest that temperature modulations of a few degrees F can be achieved by applying microsprinkler irrigation during the hottest hours of the day. This is becoming a widely accepted practice by prune growers in California with some reporting excellent results. We have created new knowledge on the reproductive biology of walnut, especially with regard to pistillate flower abortion (PFA) and the relationships between PFA and ethylene biology. Walnut cultivars that are most susceptible to PFA, especially Serr, generate greater levels of ethylene following pollination than other, less susceptible, cultivars. This ethylene can be reduced by treatment with aminovinylglycine (AVG), which inhibits ethylene synthesis. Growers have begun using AVG (as ReTain, Valent Biosciences) in Serr production

Publications

• No publications reported this period

Progress 01/01/07 to 12/31/07

Outputs
Activities: We have been conducting research and experiments in three areas. The first involves fruit set in walnut (Juglans regia), particularly walnut cultivars most severely affected by pistillate flower abortion (PFA). Field experiments using ethylene-inhibiting growth-regulator compounds aminovinylglycine and 1-MCP were continued during this reporting period. Current experiments are designed to determine carry-over effects of multiple year applications with the primary objective of determining if the enhanced set attributable to reduced PFA in Serr walnut will adversely affect subsequent yields. In order to predict the potential for PFA related loses prior to bloom we are developing a statistical model for walnut bloom based on chilling and heat unit accumulation with the objective of predicting the extent of staminate and pistillate bloom overlap. Note that PFA increases with increasing overlap. Our second research area involves determining temperature affects on prune (Prunus domestica) fruit set. Prune set has been exceptionally poor for several of the recent seasons. These years were characterized by unusually high temperatures during prune bloom. Our experiments are designed to identify threshold temperatures that adversely impact any of the three components of effective pollination: pollen germination, pollen tube growth and ovule viability. Experiments were conducted in vitro and in vivo. In vitro experiments were conducted using a temperature gradient system that creates ten temperature regimes. In vivo experiments were done with trees enclosed in temporary enclosures containing a greenhouse heater to create multiple temperature regimes. Results are modeled to determine high-temperature thresholds. Our third research project involves creating a data base of olive cultivar genotypes using the collection at the USDA National Clonal Germplasm Repository in Davis. We are also characterizing historical orchards and invasive olive populations that originated from these orchards on Santa Cruz Island. Events: Our results have been reported at the Walnut Research Conference held in Bodega Bay, California and the Prune Research Conference held in Davis California. Research summaries were given to several regional and county meetings organized by University of California Cooperative Extension. Product: We are approaching completion of a formal model to predict Serr walnut bloom overlap. Our intention is to validate our results in Spring 2008. If the model remains robust with this year's validation we expect to have it posted as an interactive web page for growers to use. One student has completed her Ph.D. and a second is on track to complete his M.S. degree this year. A third student will complete her M.S. degree in 2008.

Impacts
Outcomes for our research activities involve changes in knowledge and changes in actions. We have created new knowledge on the reproductive biology of walnut, especially with regard to pistillate flower abortion (PFA) and the relationships between PFA and ethylene biology. Walnut cultivars that are most susceptible to PFA, especially Serr, generate greater levels of ethylene following pollination than other, less susceptible, cultivars. This ethylene can be reduced by treatment with aminovinylglycine (AVG), which inhibits ethylene synthesis. Field applications of AVG show that the reduction in ethylene production is accompanied by a reduction in PFA. Interestingly, 1-MCP, which inhibits ethylene reception, leads to a marked increase in ethylene production by pollinated flowers, but is also effective in reducing PFA in the field. These results have been important in securing registration for AVG as a field treatment for PFA control in California walnut production. Growers have begun using AVG (as ReTain, Valent Biosciences) in Serr production. An important variable in PFA is the extent to which staminate and pistillate bloom periods overlap. When the overlap is extensive, the high pollen loads during pistillate bloom drive up PFA levels. Conversely, when overlap is minimal, PFA is minimal. With the goal of predicting the extent of overlap prior to the time when decisions to treat orchards with AVG, we have analyzed historical data on bloom timing and yield potential along with climate data on chilling and heat accumulation. We have found different response for staminate and pistillate bloom. Using these correlations we are developing a model to predict bloom dates and potential bloom overlap periods. We anticipate that growers will use this tool as a factor in managing orchards. Our results on prune responses to high temperatures during bloom tend to validate the recent observations and inferences regarding set. In years of high temperatures during prune bloom, set has been extremely poor. Three of the past four years have experienced such conditions. We have identified abrupt declines in pollen tube viability at threshold temperatures near the maxima observed in these years. With the looming specter of global climate changes suggesting that this may not be an isolated set of events, results such as ours may indicate that a shift in the range in prune production is imminent. The results are also of value to breeders who may begin to consider high-temperature effects on set as a selection criterion.

Publications

• No publications reported this period

Progress 01/01/06 to 12/31/06

Outputs
Walnut pollination management requires a balance between sufficient pollen to set a crop but pollen loads below a threshold that triggers pollen-induced pistillate flower abortion (PFA). We have been working toward developing management tools to control PFA by inhibiting the post-pollination ethylene response by inhibitor of ethylene synthesis (AVG) and inhibitor of ethylene action (1-MCP). AVG, as Valent Biosciences ReTain, was registered for use on walnuts for Spring 2006. Experiments have shown that AVG applications at approximately 30 percent pistillate bloom can reduce PFA in 'Serr' walnut. Results in 2006 were more variable than in previous years with some plot showing no significant effect. We found no significant reduction in PFA for 'Chandler' walnut. The most important factor in predicting the extent of PFA (and the potential benefit in PGR applications) is climate. We have prelimary data to indicate that pistillate and staminate bloom are determined by differential chilling and post-chilling heat accumulation requirements. We continue to refine a model for walnut bloom based on chilling and post chilling heat accumulation. We have developed a data base of SSR genotypes for olive cvs to identify olives in table- and oil-olive production. The results are also useful for ornamental olive cultivars in regional jurisdictions that restrict ornamental planting of olive trees to low-pollen producing cvs. We have shown that the two commonly available, low-pollen producing varieties, 'Swan Hill' and 'Wilson' can be distinguished from all other olive cultivars in our data base.

Impacts
PFA in walnuts can be controlled by growth regulators that inhibit ethylene synthesis. Preliminary results with 1-MCP indicate that it may also control PFA. Predicting the extent of bloom overlap within 'Serr' will predict the potential for losses to PFA. Our molecular markers for two specialized ornamental olive cultivars will allow these can to be validated for certification in jurisdictions that restrict ornamental landscaping to low-pollen-producing olives.

Publications

• Gratton, S.R., M.J. Berenguer, J.H. Connell, V.S. Polito, P.M. Vossen. 2006. Olive oil production as influenced by differnt quantities of applied water. Agric. Water Management 85: 133-140
• Berenguer, M.J., P.M. Vossen, S.R. Grattan, J.H. Connell, and V.S. Polito. 2006. Tree irrigation levels for optimum chemical and sensory properties of olive oil. HortScience 41: 427-432.

Progress 01/01/05 to 12/31/05

Outputs
Walnut pollination management requires a balance between sufficient pollen to set a crop but pollen loads below a threshold that triggers pollen-induced pistillate flower abortion (PFA). We have been working toward developing management tools to control PFA by inhibiting the post-pollination ethylene response by inhibitor of ethylene synthesis (AVG) and inhibitor of ethylene action (1-MCP). Results have shown promise and we expect registration of the first product for this purpose as early as Spring 2006. Walnut pollination is complicated by the heterodichogamous mating system and the fact that pollen is the vector for transmission of walnut blackline disease. We are creating research-based data on pollen flow, pollen sources, the need for pollinizer cultivars and the contribution of pollen from within and beyond orchard limits by using SSR markers for paternity analysis to follow the movement of pollen in orchard situations. Results indicate that few pollinizers are required in walnut orchards despite the dichogamous bloom habit that would appear to limit self pollination. Results show high levels of pollen from outside the orchard system play an important role in California walnut growing areas. SSR (microsatellite) markers are being shown to have great value in the analysis of gene flow in walnut orchards and they should have similar potential for use with other orchard crop species. We are developing a data base of SSR genotypes for olive cultivars. We are using this database to identify olive cultivars in table- and oil-olive production. There is an additional benefit for ornamental olive cultivars because some regional jurisdictions restrict ornamental planting of olive trees to low-pollen producing cultivars. As olives are among the most desirable ornamental trees in these locations there is a need for unequivocal identification methods for these cultivars. We have included the two commonly produced, low-pollen producing varieties in our data base.

Impacts
Our data show that PFA in walnuts can be controlled by growth regulators that inhibit ethylene synthesis. Our results indicate that losses to PFA can be reduced drastically resulting in yield increases of 50 percent or more in the most affected cultivar by AVG. Preliminary results with 1-MCP indicate that this may also be a useful management tool to control PFA. Our data on pollen flow in walnut orchards will be used to generate orchard-management strategies to design orchards to optimize set, and to effectively manage blackline disease and pistillate flower abortion. Molecular genotypes of olive cultivars will be used to identify cultivars and relationships among cultivars which will be especially useful in the emerging California olive-oil industry. We are developing molecular markers for two specialized ornamental cultivars so that these can be validated for certification in jurisdictions that restrict ornamental landscaping to low-pollen-producing olives.

Publications

• Berenguer, M.J., S.R. Grattan, J.H. Connell, V.S. Polito, and P.M. Vossen. 2004. Irrigation management to optimize olive growth, production and sensorial oil quality. Acta Horticulturae 664:79-85.
• Ferguson, Louise, Vito Polito, and Craig Kallsen. 2005. The pistachio tree; botany and physiology and factors that affect yield. The Tree, 2005. Pistachio Production Manual, pp. 31-39.
• Polito, V.S., K. Pinney, M. Aradhya, Y. Vaknin, J. Dangl, S. Weinbaum, and J. Grant. 2006 Walnut pollination dynamics: Pollen flow in walnut orchards. Acta Horticulturae. (In Press)

Progress 01/01/04 to 12/31/04

Outputs
Walnut pollination management requires a balance between sufficient pollen to set a crop but pollen loads below a threshold that triggers pollen-induced pistillate flower abortion (PFA). Management is complicated by the heterodichogamous mating system and the fact that pollen is the vector for transmission of walnut blackline disease. We are creating research-based data on pollen flow, pollen sources, the need for pollinizer cultivars and the contribution of pollen from within and beyond orchard limits by using SSR markers for paternity analysis to follow the movement of pollen in orchard situations. Results indicate that few pollinizers are required in despite the dichogamous bloom habit that would appear to limit self pollination. Results show high levels of pollen from outside the orchard system. SSR markers are being shown to have great value in the analysis of gene flow in walnut orchards and they should have similar potential for use with other orchard crop species. We are also investigating pollination parameters in olive and the role of staminate flowers in the olive breeding system. To this end we are developing a data base of SSR genotypes for olive cultivars. We are using this database to identify olive cultivars in table- and oil-olive production. Some jurisdictions restrict ornamental planting of olive trees to low-pollen producing cultivars. As olives are among the most desirable ornamental trees in these locations there is a need for unequivocal identification methods for these cultivars. We intend to expand the olive genotype database to include low-pollen producing varieties for these specialized ornamental landscape environments.

Impacts
The research on the diversity of Frankia in soil compared to that in nodules is an important contribution to the understanding of the evolution of symbiotic nitrogen fixation in plants. The work on taxonomic variation in Cercocarpus contributes to improving the classification of an ecologically important genus of shrubs in western North America. We are beginning work in Sapotaceae, a taxonomically difficult family of considerable economic and ecological importance in tropical areas which, to date, has been little studied from a molecular phylogenetic perspective. The family provides many opportunities to study evolutionary issues related to plant domestication.

Publications

• Escobar, M.A., Civerolo, E.L., Polito, V.S., Pinney, K.A., Dandekar, A.M. 2003. Characterization of oncogene-silenced transgenic plants: Implications for Agrobacterium biology and post-transcriptional gene silencing. Molecular Plant Pathology 4:57-65

Progress 01/01/03 to 12/31/03

Outputs
Walnut pollination management presents unique and complex problems for production that extends beyond fruit set. Walnut pollen carries Cherry Leaf Role Virus-Walnut, viral agent that incites blackline disease. Additionally, high pollen loads lead to reduced set due to pollen-induced pistillate flower abortion. Typical planting schemes involve planting pollinizer cultivars to provide pollen throughout the dichogamous bloom cycle of the main cultivar. We are seeking research based data on pollen flow, pollen sources, the need for pollinizer cultivars and the contribution of pollen from within and beyond orchard limits. We are using SSR markers for paternity analysis to follow the movement of pollen in orchard situations. Our efforts are concentrated on 'Chandler' orchards with 'Cisco' pollinizers. Results indicate that few pollinizers are required in this self-compatible species despite the dichogamous bloom habit that would appear to limit self pollination. Results are also showing a high level of pollen from outside the orchard system. Pollen contributions that affect production and fruit set from pollinizer trees within the orchard do not extend beyond 50 to 75 m. SSR markers are being shown to have great value in the analysis of gene flow in walnut orchards and they should have similar potential for use with other orchard crop species. We are also investigating pollination parameters in olive and the role of staminate flowers in the olive breeding system.

Impacts
We expect to elucidate the dynamics of pollen flow in walnut orchards. This information is needed to develop management strategies to optimize set, and to manage blackline disease and pistillate flower abortion both of which are related to walnut pollination.

Publications

• Cuevas, J. and Polito, V.S. 2004. The role of staminate flowers in the breeding system of Olea europaea (oleaceae): an andromonoecious, wind-pollinated taxon. Annals of Botany. (In press)

Progress 01/01/02 to 12/31/02

Outputs
We continue investigating pollen flow in walnut orchards. Pollen has a complex role in walnuts going beyond fruit set. It carries the viral agent that causes blackline disease and high pollen loads lead to reduced set due to pollen-induced pistillate flower abortion. We are using SSR markers for paternity analysis to follow the movement of pollen in orchard situations. Our efforts are concentrated on Chandler orchards with Cisco pollinizers. Results indicate that few pollinizers are required in this self-compatible species despite the dichogamous bloom habit that would appear to limit self pollination. Results are also showing a high level of pollen from outside the orchard system. SSR markers are being shown to have great value in the analysis of gene flow in walnut orchards and they should have similar potential for use with other orchard crop species.

Impacts
Results will provide a clearer understanding of the dynamics of pollen flow in walnut orchards. This information is needed to develop management strategies to manage blackline disease and pistillate flower abortion which are both related to walnut pollination.

Publications

• No publications reported this period

Progress 01/01/01 to 12/31/01

Outputs
We are investigating of pollen flow in walnut orchards. Pollen has a complex role in walnuts going beyond fruit set. It carries the viral agent that causes blackline disease and high pollen loads lead to reduced set due to pollen-induced pistillate flower abortion. We are using SSR markers for paternity analysis to follow the movement of pollen in orchard situations. We are working on the action of streptomycin on pollen tube growth and fruit set. Streptomycin has potential use as a control agent for walnut blight (Xanthomonas campestris pv. juglandis) but causes fruit drop. Our investigations suggest that this is a consequence of streptomycin-induced inhibition of pollen germination and pollen tube growth which occurs in vivo but not in vitro. Streptomycin may be acting on pistillate tissues at the stigma or style. Strawberries produced in California coastal growing regions are subject to bronzing, a disorder at the surface of the fruit that results in discoloration, tannin accumulation and unmarketable fruit. Anatomical investigations of strawberry fruits indicate that bronzing damage is consistent with sunscald injury. The cuticle is disrupted, the epidermal cell layer is destroyed and subsurface cells accumulate phenolic materials.

Impacts
Results will provide a clearer understanding of the dynamics of pollen flow in walnut orchards. This information is needed to develop management strategies to manage blackline disease and pistillate flower abortion which are both related to walnut pollination. The work on streptomycin and fruit drop provides an understanding of the biological basis for the phenomenon and will be useful in developing control strategies for walnut blight. Strawberry bronzing results in high economic losses; our work suggests causes and possible control measures.

Publications

• Cuevas, J., A.J. Diaz-Hermoso, D. Galian, J.J. Hueso, V. Pinillos, M. Prieto, D. Sola & V.S. Polito. 2001. Response to cross pollination and choice of pollinisers for the olive cultivars (Olea europaea L.) 'Manzanilla de Sevilla,' `Hojiblanca' and 'Picual.' Olivae 85:
• Escobar, M. A., Park, J.-I., Polito, V.S., Leslie, C.A., Uratsu, S.A. McGranahan, G.H, Dandekar, A.M. 2000. Using GFP as a scorable marker in walnut somatic embryo transformation. Ann. Bot. 85: 831-835.
• Nyomora, A. M. S., P. Brown, K. Pinney, V. S. Polito. 2000. Foliar application of boron to almond trees affects pollen quality. J. Amer. Soc. Hort. Sci 125: 265-270.

Progress 01/01/00 to 12/31/00

Outputs
Investigations continue in two areas. We have initiated an investigation of pollen flow in walnut orchards. Pollen has a complex role in walnuts going beyond fruit set. It carries the viral agent that causes blackline disease and high pollen loads lead to reduced set due to pollen-induced pistillate flower abortion. We have SSR markers for paternity analysis to follow the movement of pollen in orchard situations. We are working on blanking and shell split in pistachio and the possible role of pollination in affecting parthenocarpic fruit set. Our results to date indicate that the primary factor driving shell split is a generation of physical force resulting from rapid kernel growth within the endocarp. There is no indication of a biochemically mediated dehiscence event occurring at the suture lines that delineate the endocarp dehiscence zones. Tip-split may, however, differs from longitudinal split and appears to be more similar to dehiscence events in other species. Experiments following fluorescent dye markers for vascular integrity and using gamma-irradiated pollen indicate that parthenocarpy is a potentially significant factor leading to blank nut production in pistachio. We are investigating the possibility that low pollen levels may be inadequate for fruit set, but sufficient to induce parthenocarpic set.

Impacts
Results will provide the biological bases for blank nuts and unsplit shells in pistachio and the possible role of pollination. This will affect important aspects of orchard management practices, and results will enhance efficiency of pistachio production.

Publications

• No publications reported this period

Progress 01/01/99 to 12/31/99

Outputs
We continue investigations of flower development in almond involving comprehensive analysis of flower initiation and organogenesis in three cultivars in four sites in California ranging from the southern San Joaquin Valley to the northern Sacramento Valley. Emphasis is on temporal parameters and how these differ among sites and cultivars. We are developing models based on probit regression to heat unit accumulation. We are expanding this research to using molecular markers to identify critical events in floral initiation. These efforts involve identifying homologs to MAPS organ-identity genes from Arabidopsis. A second area of research involves identifying the biological mechanisms of GA-induced fruit thinning of table grapes. Among the possible biological mechanisms suggested for this practice is pollenicidal effects of GA. Our results indicate that this is not the case. We find no differences in pollen germination, pollen tube growth and ovule longevity for GA-treated or control samples. Our investigations continue on other aspects. The most likely candidate involves GA affects on cell growth in the pedicel region. A third project on blanking and shell split in pistachio has been completed. Results indicate that the primary factor driving shell split is a generation of physical force resulting from rapid kernel growth within the endocarp. There is no indication of a biochemically mediated dehiscence event occurring at the suture lines that delineate the endocarp dehiscence zones. Tip-split may, however, differs from longitudinal split and appears to be more similar to dehiscence events in other species. Experiments following fluorescent dye markers for vascular integrity and using gamma-irradiated pollen indicate that parthenocarpy is a not insignificant factor leading to blank nut production in pistachio. Previous researchers had minimized the role of parthenocarpy. Our descriptive and experimental results suggest that such inferences are in error.

Impacts
Results will provide: 1, the ability to predict timing of floral development in almond buds; 2, a biological explanation for GA-induced thinning of grapes; and 3, the biological bases for blank nuts and unsplit shells in pistachio. Each affects important aspects of orchard management practices, and results will enhance efficiency of pistachio, table grape, and olive production.

Publications

• Polito, V. S. 1999. Seedlessness and parthenocarpy in Pistacia vera L. (Anacardiaceae): Temporal changes in patterns of vascular transport to ovules. Ann. Bot. 83:363-368.
• Polito, V. S. and Pinney, K. 1999. Endocarp dehiscence in pistachio (Pistacia vera L.) Internat. J. Plant Sci. 160:827-835.

Progress 01/01/98 to 12/31/98

Outputs
We three investigations on this project. One is an investigation of flower development in almond involving comprehensive analysis of flower initiation and organogenesis in three culitvars in four sites in California ranging from the southern San Joaquin Valley to the northern Sacramento Valley. Emphasis is on temporal parameters and how these differ among sites and cultivars. We are developing models based on probit regression to heat unit accumulation. The second involves biological mechanisms of GA-induced fruit thinning of table grapes. Among the possible biological mechanisms suggested for this practice is pollenicidal effects of GA, reduction of pollen tube growth rates, reduction of ovule viability, induction of a fruit abscission zone and effects on berry growth. Our research is designed to determine which, if any, of these factors is involved. The third project involves elucidation of the cellular and structural events associated with shell split in pistachio. Results to date have indicated that there does not appear to be a clearly differentiated dehiscence zone, nor is there evidence of histochemical changes correlated with shell dehiscence. The primary factor involved appears to be physical forces resulting from rapid kernel growth and early events occurring at the time of pistil differentiation as potential factors in enabling shell split. Experimental verification of this hypothesis is in progress.

Impacts
(N/A)

Publications

• HORMAZA, J.I., PINNEY, K., AND POLITO, V.S. 1998. Genetic diversity of pistachio (PISTACIA VERA L.) based on randomly amplified polymorphic DNA (RAPD) markers. Econ. Bot. 52:78-87.
• FABBRI, A., FERGUSON, L., AND POLITO, V.S. 1998. Crop load related deformity of developing Pistacia vera cv 'Kerman' nuts. Scientia

Progress 01/01/97 to 12/01/97

Outputs
We have initiated three new projects this year. One is an investigation of flower development in almond. This is a comprehensive analysis of flower initiation and organogenesis in three cultivars in four sites in California ranging from the southern San Joaquin Valley to the northern Sacramento Valley. Emphasis is on temporal parameters and how these differ among sites and cultivars. The long term objective is to relate our data to environmental conditions, especially heat unit accumulation. The second involves biological mechanisms of GA-induced fruit thinning of table grapes. Among the possible biological mechanisms suggested for this practice is pollenicidal effects of GA, reduction of pollen tube growth rates, reduction of ovule viability, induction of a fruit abscission zone and effects on berry growth. Our research is designed to determine which, if any, of these factors is involved. The third project involves elucidation of the cellular and structural events associated with shell split in pistachio. Results to date have indicated that there does not appear to be a clearly differentiated dehiscence zone, nor is there evidence of histochemical changes correlated with shell dehiscence. We are investigating the possible role of physical forces resulting from rapid kernel growth and early events occurring at the time of pistil differentiation as potential factors in enabling shell split.

Impacts
(N/A)

Publications

• POLITO, V.S. AND PINNEY, K. 1997. The relationship between phenology of pistillate flower organogenesis and mode of heterodichogamy in JUGLANS REGIA L. (Juglandaceae). Sexual Plant Reproduction 10:36-39.

Progress 01/01/96 to 12/30/96

Outputs
We have been investigating gametophytic expression of sporophyte tolerance to ozone in several Rosaceae tree-crop species. We based our research on findings by others that there are differential sensitivities to ozone stress among species of Rosaceous tree-crops and among almond cultivars. We examined the relative sensitivities to ozone for male gametophyes (pollen and pollen tubes) of the same species and cultivars. Pollen germination was sensitive to ozone stress, but did not correlate with the relative sensitivities of the sporophytes. Pollen tube growth was also sensitive to ozone in the range of 0.2 to 0.6 ppm. Pollen tube growth showed near complete correlation with sporophytes: tolerant sporophytes produced tolerant pollen tubes and vice versa. This finding indicates that pollen tube growth may be a useful screening method for identifying ozone-tolerant selections. Our research into this phenomenon continues. We are extending these results to an investigation of effect of ozone stress on pollen tube growth in vivo. If we can demonstrate that ozone stress favors the growth of ozone-tolerant pollen tubes in vivo, the results open the possibility of devising competition experiments to determine if ozone selection pressure applied to growing pollen tubes in vivo can favor the production of ozone-tolerant progeny.

Impacts
(N/A)

Publications

• HORMAZA, J.I. and POLITO, V.S. 1996. Correlation in the tolerance to ozone between sporophytes and male gametophytes of several fruit and nut tree species (Rosaceae). Sexual Plant Reproduction 9:44-48.

Progress 01/01/95 to 12/30/95

Outputs
We have been investigating sex expression in the dioecious tree species, PISTACIA VERA, pistachio. Our research has focused on identifying molecular markers for sex expression using Random Amplified Polymorphic DNA techniques. We used a bulked segregant analysis strategy that involved using random decamer oligonucleotide primers to amplify pooled DNA from pools of male and female full siblings from each of two crosses. We have identified bands specific to females. One is present in all females comprising the pools and in all individual females examined. We propose that this marker (OPO-08-945) is closely linked to gene(s) determining femaleness and that it is a valid marker for the female genome in seedling pistachios. The amplification product has been sequenced and SCAR primers generated in an effort to increase the rigor of the test. This approach has produced new bands. Hybridization to genomic DNA suggests that repetitive DNA may be involved. We have also applied RAPD polymorphisms to cultivar identification in pistachio and olive. A third project demonstrates gametophytic expression of sporophyte tolerance to ozone in several Rosaceae tree-crop species. This finding indicates that pollen germination and tube growth may be a useful screening method for identifying ozone-tolerant selections.

Impacts
(N/A)

Publications

Progress 01/01/94 to 12/30/94

Outputs
We have been investigating sex expression in the dioecious tree species, PISTACIA VERA, pistachio. Our research has focused on identifying molecular markers for sex expression using Random Amplified Polymorphic DNA techniques. We used a bulked segregant analysis strategy that involved using random decamer oligonucleotide primers to amplify pooled DNA from a male and a female pool of each of two full sibling crosses. 'Peters' was the male parent for each cross and 'Kerman' and 'Lassen' were the female parents. We analyzed 1200 primers. Three of these produced bands that were specific to females in the bulked samples. When tested against DNA from the individuals comprising the crosses, no males were positive for the bands. For two of these, not all the females were positive. We propose that these bands may be linked, although not closely, to the gene(s) that determine femaleness in pistachio. The third band was present in all females comprising the pools and in all individual females outside the pool. We propose that this marker (OPO-08-945) is closely linked to gene(s) determining femaleness and that it is a valid marker for the female genome in seedling pistachios. The OPO-08-945 segregates consistent with a 1:1 ratio in seedling populations of unknown sex. Amplified bands have been sequenced and SCAR primers generated in an effort to increase the rigor of the test. This approach has produced new bands.

Impacts
(N/A)

Publications

Progress 01/01/93 to 12/30/93

Outputs
We have been investigating sex expression in the dioecious tree species, PISTACIA VERA, pistachio. Our research has focused on identifying molecular markers for sex expression using Random Amplified Polymorphic DNA techniques. We used a bulked segregant analysis strategy that involved using random decamer oligonucleotide primers to amplify pooled DNA from a male and a female pool of each of two full sibling crosses. 'Peters' was the male parent for each cross and 'Kerman' and 'Lassen' were the female parents. We analyzed 1200 primers. Three of these produced bands that were specific to females in the bulked samples. When tested against DNA from the individuals comprising the crosses, no males were positive for the bands. For two of these, not all the females were positive. We propose that these bands may be linked, although not closely, to the gene(s) that determine femaleness in pistachio. The third band was present in all females comprising the pools and in all individual females outside the pool. We propose that this marker (OPO-08-945) is closely linked to gene(s) determining femaleness and that it is a valid marker for the female genome in seedling pistachios. The OPO-08-945 segregates consistent with a 1:1 ratio in seedling populations of unknown sex. It is our intent to validate the marker against seedling populations that should attain sexual maturity in 1994.

Impacts
(N/A)

Publications

Progress 01/01/92 to 12/30/92

Outputs
Continuing investigation into pistillate flower abscission in walnut has shown that excess pollen is clearly a factor correlated with pistillate flower abscission in 'Serr' walnut. Pistillate flower abscission is inversely correlated with distance from pollinizer cultivars and positively correlated with number of pollen grains on the stigma. The opposite correlations hold for crop yield, underscoring the importance of this phenomenon. Preliminary investigation into the mechanisms whereby excess pollen leads to pistillate flower abscission has implicated ethylene as a possible factor. Ethylene is produced by flowers approximately 24 hours after pollination. Serr, a cultivar that shows high sensitivity to pollen-induced flower abscission, produces more than twice the ethylene than does Sunland, a non-abscising cultivar. Dead pollen at high levels is as effective at inducing abscission as live pollen at the same dose level. Dead pollen also causes a comparable ethylene response. Attempts at using inhibitors of ethylene synthesis and ethylene action were inconclusive and will be repeated in 1993. Field experiments were conducted to devise strategies to mitigate pollen-induced pistillate flower abscission. These included removing pollinizer cultivars from the orchard and shaking pollinizer trees prior to staminate bloom to remove catkins. Both approaches showed some reduction in flower abscission. Dichogamy is a factor, however.

Impacts
(N/A)

Publications

Progress 01/01/91 to 12/30/91

Outputs
There are four sets of results for this project: 1. Continuing investigations into pistillate flower abscision in walnut has shown that excess pollen is clearly a factor correlated with pistillate flower abscission in 'Serr' walnut. Pistillate flower abscission is inversely correlated with distance from pollinizer cultivars and positively correlated with number of pollen grains on the stigma. The opposite correlations hold for crop yield underscoring the importance of this phenomenon. Investigation into the mechanisms whereby excess pollen leads to pistillate flower abscission continues. 2. Adaptive responses of walnut pollen to temperature were demonstrated to be at least partially a phenotypically plastic response. Experiments designed to separate the environmental and genetic influences showed that at least half of the response showed by the species can be evoked in a single genotype by manipulating the temperatures during pollen development. Investigations into mechanisms with a focus on changing lipid contents of the pollen grain are ongoing. 3. Research on pollination effects on worthless shotberry and sound fruit production in olive demonstrated that the pollinizer cultivar can influence these parameters. 'Manzanillo' pollinated by 'Ascolano' produced high parthenocarpic shotberries and low sound fruit; the opposite was found with a 'Sevillano' pollinizer.

Impacts
(N/A)

Publications

Progress 01/01/90 to 12/30/90

Outputs
Work on this project has addressed three major problem areas: pollen temperature relationships in walnut, membrane-cytoskeleton interactions in pollen germination and tube growth, floral biology of walnut and olive. We showed that pollen germination responses to temperature in several species are correlated with relative earliness of bloom; both the ability to tolerate low temperature and optimum germination temperature. Pollen from earlier cultivars and clones show lower temperature optima for germination that of later cvs. Experiments in walnut indicate that this may not be genetically determined, but a consequence of the temperature experienced during the period of pollen development. Examination of potentially floral shoot apices in olive indicated that floral evocation occurs considerably earlier than previous literature had suggested. Pollen tube growth in walnut was shown to be either chalazogamous or porogamous, with the difference depending on the degree of ovule development at the time of pollination. In olive field experiments we demonstrated the value of using supplementally applied `Sevillano' pollen to increase set and reduce shotberry production in `Manzanillo' orchards. Investigations of cytoskeleton dynamics during pollen germination have revealed microtubules, unlike microfilaments, are initiated and organized during the activation process.

Impacts
(N/A)

Publications

Progress 01/01/89 to 12/30/89

Outputs
Work on this project has addressed four major problem areas: pollen temperaturerelationships in pistachio and walnut, somatic embryogenesis in walnut, calcium-cytoskeleton intteractions in pollen germination and tube growth, and cell calcium dynamics during stress. Pollen germination responses to temperature show a correlation between relative earliness of bloom and both th ability to tolerate low temperature and optimum germination temperature. Pollen from earlier cultivars and clones show lower temperature optima for germination than that of later cultivars. Experiments in walnut indicate that this may not be genetically determined, but a consequence of the temperature experienced during the period of pollen development. Examination of somatic embryogenesis in walnut reveal that embryos arise from single surface cells. Following Agrobacterium-mediated transformation such embryos develop as non-chimeric transformed plants. Investigations of cytoskeleton dynamics during pollen germination have revealed that pollen in the dehydrated state contains actin stored in an oligomeric form evident following rhodamine-phalloidin staining as circular profiles probably representing spherical bodies 2-3 mu m in diameter. During the 30 minutes preceding germination the actin udergoes marked structural changes which correlate with temporal and spatial events that occur in the germinating pollen gain.

Impacts
(N/A)

Publications

Progress 01/01/88 to 12/30/88

Outputs
Work on this project has addressed three major problem areas: blank nut production in pistachio, pollen temperature relationships in pistachio and walnut, and calcium-cytoskeleton interactions in pollen germination and tube growth. Using fluorescent tracers for continuity of vascular transport we have shown that patterns of transport into pistachio ovules and developing kernels is correlated with blanking. Results indicate that blanking probably has more than one basis; it may be caused by embryo abortion or by parthenocarpic fruit development. Embryo abortion may be subject to manipulation by appropriate orchard management practices; parthenocarpic fruiting is probably a genetically determined characteristic that is likely to be intractable to amelioration by management. Pollen germination responses to temperature show a correlation between relative earliness of bloom and both the ability to tolerate low temperature and optimum germination temperature. Pollen from earlier cultivars and clones show lower temperature optima for germination than that of later cultivars. Preliminary experiments indicate that, in walnut, this may not be genetically determined, but a consequence of the temperature experienced during the period of pollen development.

Impacts
(N/A)

Publications

Progress 01/01/87 to 12/30/87

Outputs
Blank nut production in pistachio is associated with temporal variation in vascular transport activity within the growing fruit. In 'Kerman' pistachio fruits the first division of the zygote does not occur for 10-12 weeks after bloom. For several weeks prior to this time there is complete blockage of vascular transport to the ovule as indicated by movement of fluorescent probes for vascular function. At the time embryo growth begins transport resumes in approximately 80% of the fruits. This correlates well with the percentage of filled nuts. The extent to which this relationship is causal or symptomatic is unclear. Research with pistachio pollen has indicated that previous reports greatly underestimated it longevity at ambient conditions or in storage. In vitro germination rates following incubation in a humid atmosphere indicate that for 'Peters' pollen, viability greater than 50% is retained for up to three weeks at ambient and up to one year at -20C and 33% RH. The pollen also survived liquid nitrogen storage with no loss of germinability. Investigations on interactions between Ca and the cytoskeleton during pollen hydration nd germination have indicated that pools of oligomeric actin are rapidly mobilized into extensive arrays of microfilaments during pollen hydration.

Impacts
(N/A)

Publications

Progress 01/01/86 to 12/30/86

Outputs
Walnut Reproductive Biology: Methods have been developed for storage and viability testing of walnut pollen. In vivo pollen tube growth has been defined; results indicate that entry of the pollen tube into the ovule may be porogamous or chalazogamous and that pollen tubes are evident in the nucellus by 60 hr after pollination of receptive pistillate flowers. A relationship between the phenology of anther and pollen development and the mode of dichogamy expressed by a given cultivar has been established: protandrous cultivars enter the dormant period with a more advanced stage of anther development and resume staminate flower development sooner than protogynous cultivars. Pistachio Reproductive Biology: Methods have been developed for storage and viability testing of pistachio pollen. Phenology of vascular transport into ovules has been characterized and the results are relevant to the production of blank nuts. Olive flowering: Results of structural and quantitative cytochemical investigations indicate that floral induction occurs as early as mid-November in olive buds. Almond Pericarp Dehiscence: A role for ethylene has been demonstrated in the dehiscence of the almond pericarp. The dehiscence zone is characterized by cells with thick, primarily pectinaceous walls that undergo similar cytochemical changes upon the onset of natural or ethylene-induced dehiscence.

Impacts
(N/A)

Publications

Progress 01/01/85 to 12/30/85

Outputs
Walnut flower biology. Methods for walnut pollen storage and viability testing have been refined. Critical factors are moisture status of pollen and regulation of hydration during germination. Correlations between moisture content and germinability in vitro indicate that at pollen population moisture content of 3.94%, 50% germinability is lost. Storage in at -20C is possible if relative humidity is maintained at or near 30%. Storage in liquid nitrogen depends upon pollen moisture content being between 4 and 6%. Developmental studies indicate that the mode of heterodichogamy in walnut clones has its basis in the phenology of pistillate flower differentiation during the weeks following anthesis. Almond Flower Biology and Fruit Dehiscence. The role of ethylene in pollen-ovule interactions has been examined and resultes indicate that there is a burst of ethylene evolution in cross-pollinated flowers that correlates with the onset of rapid ovule differentiation. Neither the ethylene burst nor the differentiation events occur in self or non-pollinated flowers. Histochemical and cytochemical analyses of fruit dehiscence indicate that the dehiscence separation zone is comprised of a well differentiated layer of thick-walled cells whose walls stain positively for pectin, but not other cell wall polymers. As dehiscence progresses separation zone pectin content declines.

Impacts
(N/A)

Publications

Progress 01/01/84 to 12/30/84

Outputs
Walnut flower biology. Methods for walnut pollen storage and viability testing have been refined. Critical factors have been shown to be hydration during germination and the moisture status of pollen. Walnut pollen was found to have extremely low moisture content at dehiscence. Correlations between moisture content and viability indicate that at a population moisture content of 3.94%, 50% viability is lost. Storage in LN(2) is possible for walnut pollen. Flower development studies indicate that heterodichogamy in walnut has its basis in developmental events occurring during the spring flush of growth during the growing season before bloom. Almond flower biology. Cellulsar and physiological interactions involving compatible pollen tubes in the style and normal embryo sac development have been identified and ethylene production by pistillate tissue following cross-pollination has been implicated in this relationship. Comparisons with self compatible peach cvs have indicated that early events in the self incompatibility response involve inhibition of pollen germination. Calcium, calcium-dependent regulatory proteins and pollen tube growth. Results have indicated that CayRG and CDRP's are involved in the hydration and reestablishment of membrane integrity during pollen hydration. Immunocytochemical studies of the role of CDRP's during pollen hydration and tube growth are in progress.

Impacts
(N/A)

Publications

Progress 01/01/83 to 12/30/83

Outputs
Walnut Flower Biology. Methods for evaluating walnut pollen storage have been developed. This has included a system for in vitro pollen germination, controlled hydration of pollen prior to germination, and regulation of hydration prior to during storage at -20oC. Pollen tube growth in vivo has been studied and the pollen tube growth path and timing of progamic phase re-evaluated. Protrogyny in walnut cultivars has been shown to have its developmental basis in the events preceding the onset of dormancy in the fall. Almond Flower Biology. Interactions between compatible pollen tubes in the style and normal development of the almond embryo sac have been identified and initial characterization has been completed. The possible role of ethylene in the response is under continuing investigation. Juvenility and Reproductive Maturation. Analysis of cell populations at the shoot apical meristem of Hedera helix has shown that neither endopolyploidy nor DNA amplication at levels detectable by Feulgen cytophotometry or EM morphometrics are associated with phase change in this species.

Impacts
(N/A)

Publications

Progress 01/01/82 to 12/30/82

Outputs
Pollen biology: Walnut pollen germination In Vitro indicates a rapid loss of viability under ambient conditions of pollen from 15 cultivars of English walnut. Germinability was obtained for three months following -20 degrees C storage longer storage times resulted in loss of germinability. Preliminary results indicate that liquid nitrogen storage of English walnut pollen is feasible and additional trials are planned. Studies of subcellular Ca 2 + distribution kinetics during pollen germination indicate that Ca 2 + movement from membrane sites into the free cytoplasm and/or the external medium occurs upon pollen grain hydration. Calmodulin inhibitors interfere with this movement of subcellular Ca 2 + is reloaded onto membrane sites in the vicinity of the germination aperature and remains associated with membranes at the tip of growing pollen tubes. Alternate bearing in olive: gross morphological differences were noted between the lateral buds (potential inflorescence buds) of bearing and non-bearing 'Manzanillo' trees. Meristem cell populations with these buds are currently being investigated to determine if these differences extend to the cells of the apical meristem as well. Indications of floral induction several weeks prior to what has been reported in the literature have been noted and these results are being followed and expanded.

Impacts
(N/A)

Publications

Progress 01/01/81 to 12/30/81

Outputs
Almond ovule abortion is preceded by the deposition of "callose" at the chalazalend of the ovule. As ovule abortion progresses "callose" deposition extends acropetally throughout integrumentary tissues of the ovule. Movement of fluorescent tracers indicates that blockage of translocation into the ovule follows the "callose" reaction and preceeds any morphological indication of ovulue abortion. Studies on growth of callus cultures derived from shoot apex cells reveal that these cells respond in a manner consistent with determined cells. Results indicate that phase-related differences characteristic of differentiated cells may be expressed in the undifferentiated cells of the meristem as well. In vitro germination of 'Franquette' walnut pollen was optimal on medium containing 25% sucrose and 10MuM CA + 2. Pollen density in the medium was the most significant variable examined. Regions of highest density supported higher rates of germination than regions of lower density. Study of in vivo growth of walnut pollen tubes was facilitated by the development of a method that allows examination of paraffin-embedded material for anilineblue-induced fluorescence in the pollen tubes and simultaneous bright field staining of ovarian tissues. Preliminary results using this technique indicated that at least eight days are required for pollen tubes to grow from stima surface to the ovule.

Impacts
(N/A)

Publications

Progress 01/01/80 to 12/30/80

Outputs
Anatomy and histochemistry of olive leaf abscission following ethephon treatmentrevealed that the leaf abscission zone is structurally similar to the pedicel-peduncle but distinct from the abscission zone at the distal end of the pedicel. This suggests a basis for selectively inducing fruit abscission. Maturation phenomena have been examined in callus cultures derived from adult and juvenile phase meristems and stem tissues. Adult phase callus growth rate were less than those of juvenile-phase callus in each case. Results indicate intrinsic physiological differences, retained by division products in vitro and in vivo, characterize cells of adult and juvenile phase meristems. Walnut fruit growth and kernel growth each follow a double sigmoid pattern with periods of high rates of kernel growth coincident with periods of low rates of total fruit growth. The pattern observed as qualitatively and quantitatively similar in Ashley and Hartley.

Impacts
(N/A)

Publications