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Lindcove Research and Extension Center
22963 Carson Avenue
Exeter, CA 93221
Phone: (559) 592-2408

Citrus

164 - Breeding for HLB-resistant Citrus and Field Evaluation of Hybrids

Prinicipal Investigator: Dr. Chankdrika Ramadugu, Dept of Botany and Plant Sciences, UC Riverside.

In our breeding program conducted at the Citrus Variety Collection, UC Riverside, we have generated hybrids of citrus by crossing with Australian limes. Our goal is to generate hybrids with huanglongbing resistance/tolerance and acceptable fruit quality. Three hybrid-accessions will be planted at Lindcove REC to conduct horticultural evaluations.

163 - Decision Support Tools for Spatiotemporal Integration of Citrus Virtual Orchard and Soil Sensing

Increasing yield, improving fruit quality, and optimizing harvesting operations are the priorities of the citrus industry in California. These needs will be addressed by integrating high resolution soil mapping and time-lapse virtual orchard (VO, i.e., 3-dimensional maps of an orchard) in visible, near-infrared, and thermal bands. The main objectives of this research project are, 1) to integrate soil mapping and VO information to predict yield, fruit quality, and optimal ripening time, and 2) to create a user- friendly web platform for the management, analysis, and interpretation of the soil and crop data.

162 - Movement Patterns of Invasive Roof Rats in Citrus

Roof rats can cause extensive damage in a number of tree crops including citrus. Roof rat populations seem to be expanding and growing throughout many agricultural regions in CA, yet management options for limiting this damage have been largely unsuccessful. The development of an integrated pest management (IPM) program could greatly reduce this damage, but such a program is challenging to develop without at least a basic understanding of the general biology and ecology of the pest species within the target system. As such, we propose a project using new cellular-tracking technology to gain a better understanding of roof rat movement patterns to better target management programs. We also plan to test the utility of tracking tunnels and remote-triggered cameras to serve as quantitative indexing tools to track changes in population size following the implementation of various management tools. Collectively, this information will serve as the foundation for a subsequent study designed to assess the utility of potential control options for reducing roof rat numbers in citrus and related orchard cropping systems in CA.

161 - Studies of Asian Citrus Psyllid Behavior

Principal Investigator: Dr. Monique Rivera, Entomology Specialist, Dept of Entomology, UC Riverside.

The purpose of this project is to study the effects of ladybug trails on ACP phloem-feeding on citrus and if ladybug trails can effectively reduce phloem-feeding attempts by ACP. This research may potentially have a positive impact on citrus production across the country because our research may suggest a new cost-effective method to decreasing the acquisition of HLB in citrus by ACP. We propose for citrus plants to be created at LREC so that we can continue our ACP phloem-feeding study and increase treatment replicates with citrus plants.

160 - Citrus Spray Application Expert System

Principal Investigator: Dr. Peter Larbi, Engineering Specialist, UC ANR Kearney Research and Extension Center.

An expert system (ES) is a computer program that simulates the judgment of an individual or organization possessing expert knowledge and experience in a particular field. The existing ES (CitrusSprayEX) was designed to provide decision support for spray applicators who use air-carrier sprayers (specifically airblast sprayers) to apply pesticides to citrus canopies. However, in this project, we will use it: i) as a planning and evaluation tool for applicators and their supervisors; ii) as a training tool for pesticide training meetings; and iii) as an educational tool for agricultural students at the high school and college level. This effort is intended to create a general awareness of the need for efficient spray application and provide an active and specific guidance on how to achieve it in complex field situations.

159 - Capturing Pheonypic Variation in Fruit Across Diverse Citrus Germplasm

Principal Investigator: Dr. Danelle Seymour, Dept of Botany and Plant Sciences, UC Riverside.

A major limitation to modern breeding is the ability to rapidly and affordably collect phenotypic data. Without high quality phenotypic information our ability to characterize the genetic basis of traits important, in our case, to the California citrus industry is limited. We propose to leverage the fruit grading system on the packline located at Lindcove Research and Extension Center to produce a high-throughput, comprehensive data set of fruit characteristics across a diverse set of citrus germplasm. This data set will enable us 1) to characterize the degree of phenotypic variation in fruit traits within and between citrus varieties, 2) to determine whether fruit traits share a genetic basis, and 3) to identify gene-trait associations that can be used for marker-assisted breeding. We expect that this high-throughput survey of fruit traits will deepen our understanding of the genetic basis of fruit characteristics in citrus and serve as a foundation for future breeding decisions.

158 - Optimization of Cultural Practices in Citrus

Prinicipal Investigator: Dr. Ashraf El Kereamy, Horticultural Specialist, Dept of Botany and Plant Sciences, UC Riverside.

New cultural practices are needed to help the citrus industry in maximizing its production and improving its efficiency while facing ongoing and emerging challenges. Various trials will be carried out to optimize several cultural practices to improve citrus fruit quality and production, optimize nutrition use efficiency, improve tolerance to abiotic stress, and reduce preharvest disorders. This project will provide the citrus industry with a comprehensive guideline on the horticultural practices (pruning, irrigation, fertilization, growth regulators) that can be used to optimize its production.

157- UCSB-Lindcove SmartFarm

Principal Investigator: Dr. Chandra Krintz, Professor of Computer Science, University of California, Santa Barbara.

SmartFarm is a new, unifying, and open approach to agriculture analytics and precision farming that leverages and integrates IoT (Internet of Things) and cloud technologies to provide farmers with new sensing, decision support, and data-driven actuation and control. This project proposes to develop and deploy SmartFarm at Lindcove and use it to investigate, validate, and demonstrate new approaches for sensing, data analytics and machine learning, and actuation of farm operations for citrus. In particular, it will use the UCSB-Lindcove SmartFarm system to investigate data driven frost damage mitigation for citrus.

155 - Evaluation of Lilac Lime Productivity and Fruit Quality

Principle Investigator: Dr. James Thomson, Research Geneticist, USDA-ARS Albany CA

The goal of this project is to produce a transgenic citrus variety that was visually appealing to the consumer for marketing purposes and public opinion/feedback gathering. Genome modified Mexican lime lines, termed ‘Lilac Limes’ will be grown at Lindcove Research and Extension Center and tree health, fruit color pattern, nutrition, fruit production/quality and flowering time will be monitored. Lilac limes will serve as a flagship for federal deregulation of a genome modified citrus tree. If deregulated, they can enter into the commercial market as a unique and appealing colored lime with antioxidant features.

154 - Citrus Under Protective Screen (CUPS) for HLB Management

Principal Investigator: Dr. Philippe Rolshausen Associate CE Specialist, University of California, Riverside.

This project designed to study that measures the long-term performance of trees under protective structure and develop horticultural technologies to improve CUPS production performance and sustainability. In addition, to seek evidence that this approach is an economically viable near-term alternative to grow HLB-free citrus. A plan to build the structure at Lindcove is in progress to address the scientific objectives.

151 - Cold treatment as a non-chemical alternative for postharvest management of bean thrips (Caliothrips fasciatus Pergande)

Principal Investigator: Dr. Sandipa Gautam, Dept of Entomology, UC Riverside.

Bean thrips (Caliothrips fasciatus), native to USA, is a pest of export significance to the citrus industry because this species overwinters in the navel of navel oranges. California citrus growers practice a system’s approach that includes fruit cutting and inspection prior to harvest to check for thrips and postharvest treatment using CropFume for controlling bean thrips in fruit destined for Australian markets. Despite following the system’s approach, bean thrips interceptions have continued, and given the lack of effective alternative postharvest treatment research is needed to find a more effective postharvest alternative. Early, mid, and late season fruit will be used to evaluate the efficacy of cold treatments on bean thrips and to highlight the differences in susceptibility to the quarantine treatment between commercially important navel and mandarin strains used in California.

150 - Evaluating Serenade, Aliette, and Velum to improve citrus health and productivity

Principal Investigator: Dr. Greg Douhan, Area Citrus Advisor, Cooperative Extension Tulare County

Citrus producers face challenges in the form of nematodes, disease, and crop health in addition to the highly likely advance and spread of ACP and the accompanying devastating HLB disease. The research proposed here is aimed at increasing Citrus health, reducing disease and nematode damage, in preparation for the advance of HLB into the southern San Joaquin Valley. This research will test 3 compounds individually, and all 3 in combination to determine their effects at mediating nematode and disease issues and to determine their effects on improving Citrus plant health. The Lindcove Research and Extension Center was chosen as a representative site for the southern San Joaquin Citrus growing region and provides the ideal opportunity to examine the effects of these treatments in detail.

149- Citrusformatics IPM field experiments for pests of citrus

Principal Investigator: Dr. Jay A. Rosenheim, University of California, Davis, Department of Entomology and Nematology

Citrus production in California has changed dramatically in recent years, with a sharp increase in mandarin acreage. In the absence of existing research into key endemic arthropod pests in mandarins, our current integrated pest management (IPM) guidelines have been largely borrowed from the years of extensive research done on oranges. We know these two crops are different in many ways, but not which pest management practices to change for optimal production. This project takes an integrated experimental and database (Citrusformatics IPM database) approach to address the formidable challenge of adapting IPM to a new crop. Preliminary analyses of the Citrusformatics IPM database, which contains comprehensive pest management data and harvest data from commercial growers in the in the San Joaquin Valley, has revealed some surprising patterns concerning key pests of citrus. At the Lindcove Research and Extension Center, we are testing different explanatory hypotheses for these trends. Our current experiments focus on fruit abscission, and damage from katydids and citrus thrips in different varieties of oranges and mandarins. Combining these field experiments with analyses of the data from industry contributors can help to provide timely, accurate and broad-scale recommendations to growers and pest control advisors, as the invasion of the Asian citrus psyllid (ACP) places new pressures on pest management practices.

143- Rootstock Trial for Lisbon Lemon

Principal Investigator: Dr. Mikeal Roose, Botany and Plant Sciences, University of California Riverside

Cooperator Glenn Wright of U. Arizona evaluating the lemons

The proposed research project is to establish a rootstock trial for Limoneira 8A Lisbon lemon at Lindcove Research and Extension Center as part of a series of three trials to evaluate several new rootstocks in the San Joaquin Valley, the Ventura County area, and in the Coachella Valley. Trees of Limoneira 8A Lisbon lemon, a popular selection in California, have been propagated at B&Z Nursery in a certified insect resistant greenhouse. The trees are on 11 rootstocks, 8 of which have not been tested previously with lemons at Lindcove. A total of 132 experimental trees (11 rootstocks x 12 single tree replications) are available. Guard trees should also be available if there is space. We have a higher probability of obtaining yield data on trials at Lindcove than for trials with grower-cooperators. Having this trial at Lindcove also facilitates analysis of the fruit on the packline. Trees will be ready for planting in March 2016. They will be planted in a row-column design with 12 replications and single-tree plots. Normal cultural practices should be applied by Lindcove staff.

127 - Infrastructure support for research on detection and management of HLB and ACP

Principal Investigator: Dr. Kris Godfrey, UC Davis, Director of the Contained Research Facility.

The disease/insect complex of huanglongbing (HLB)/Asian citrus psyllid (ACP) is threatening the California citrus industry. Basic research on this complex can only be conducted in approved quarantine facilities in California such as the University of California-Davis Contained Research Facility (CRF). The CRF is a Biosafety Level III – Plant facility, and no living organism or viable part of an organism can leave the facility. This project will provide the plant material (seeds) needed to conduct basic research on early detection of HLB (i.e., detection before symptom development) and management of ACP. Maintenance of the HLB culture and ACP colonies requires a constant supply of citrus plants in the appropriate phenological stage due to plant mortality caused by both the insect and the disease. The plants must be started from seed as is required by the Standard Operating Procedures (SOP) of the CRF. The cultures and colonies within the CRF will be used by as many as nine projects (research on various methods for early detection of HLB and novel management tactics for ACP) supported by the Citrus Research Board. This project at the Lindcove Research and Extension Center will help to insure that there are enough quality citrus plants produced from seed, to maintain the HLB cultures and the ACP colonies needed for research.

112 - Rootstock Trials for Clementine and DaisySL Mandarins

Principal Investigator: Dr. Mikeal Roose, Botany and Plant Sciences, University of California Riverside

The objectives of this project are to evaluate the performance of three mandarin scions on a range of commercial and experimental rootstocks. Mandarins are of increasing importance in California and frequently have compatibility problems with some commonly used rootstocks. We selected 20+ rootstocks, collected seeds and propagated trees at Lindcove. Tree were budded with 'Nules' Clementine, 'DaisySL' mandarin and 'Sidi Aissa' Clementine. There are currently relatively few rootstock trials for mandarins in California so it is important to initiate new trials. Tree size, health, crop and fruit quality data will be collected as the trees mature.

098 - Multi-location, Replicated Trials of Promising Citrus Scion Varieties for California

Principal Investigator: Dr. Tracy Kahn, Botany and Plant Sciences, University of California Riverside

A series of citrus variety trials have been initiated to systematically evaluate the most promising new scion cultivars in locations that represent the major California citrus production zones. Currently, new scion varieties that are imported into California are evaluated in trials of 1-3 trees at a few locations (UCR, Lindcove, and Thermal). Varieties developed in the UCR breeding program are evaluated in replicated trials at 7 locations, but these trials do not always compare new selections with many existing cultivars. This proposal will establish integrated trials that can include new varieties regardless of origin and standard cultivars that represent each major group. One of the locations chosen for these multi-location replicated trials is Lindcove. The trials will have sufficient replication (18 trees per location, 5 locations) to make it possible to estimate yields and measure fruit quality traits with a reasonable degree of accuracy. Promising imported Satsuma and Clementine scion selections were chosen for the first set.

075 - IR-4 Pesticide Residues

Principal Investigator: Dr. Jeff Dahlberg, Kearney Agricultural Center

The Inter-regional Research Project #4, or IR-4, was created by the U.S Department of Agriculture (USDA) in 1963 to aid growers of high-value specialty crops in obtaining pesticide registrations that would otherwise be unavailable. For a pesticide to be labeled for use, a tolerance, or the legal allowable limit of pesticide residues, must be established on that crop. The cost to register pesticides for specialty crops far exceeds the purchases made by the growers and packers. In response, the publicly funded national IR-4 Project was established to facilitate pest management solutions for specialty crop growers. Citrus, avocados and olives are specialty crops. By facilitating the registration of new pesticide uses in these crops, the IR-4 project helps the growers and packers use safer pesticides, use existing pesticides in more ways, have access to enough pesticides to help reduce the development of pesticide resistance in the pest populations, respond to invasive or new pests, and/or increase export market potential. This is done by having trials throughout the United States that mimic commercial practices, apply new pesticides to commodities, and send samples for analysis of residues. The field and lab data package is sent to EPA so that tolerances can be set and the new (often reduced-risk) pesticides or new uses of existing pesticides can be registered. The permanent plantings at Lindcove REC are used to conduct IR-4 trials on citrus, avocado and olive crops.

056 - Citrus Variety Evaluation Orchard

Principal Investigator: Dr. Tracy Kahn, Department of Botany and Plant Sciences, University of California Riverside

During the past decade there have been significant changes in the number, types and varieties grown in California due in part to market changes within the global market for fresh citrus, and the increase in foreign imports and exports with intensified global competition. High quality citrus varieties which meet the market needs and are suited to California climates are crucial to the California citrus industry to maintain competitiveness in the global and domestic fresh citrus market. New varieties are released each year from the Citrus Clonal Protection Program (CCPP) which may have commercial potential for the California Citrus industry. The Lindcove Research & Extension Center (LREC) Variety Demonstration Orchard has two main objectives: 1. Provide a demonstration block of new and existing citrus cultivars for field days, fruit displays and for growers and industry representatives to evaluate fruiting trees of these varieties, and 2. Serve as a resource to other citrus research projects and for our CRB-funded projects which provides preliminary evaluation new citrus varieties entitled: Citrus Variety Evaluation for Trueness-to-Type and Commercial Potential. The majority of the varieties in the collection are grown on each of two rootstocks; Carrizo citrange and C-35 citrange, or the most appropriate rootstock for the specific scion variety. Data collected on the fruit quality traits of new citrus varieties at the LREC Citrus Variety Demonstration Orchard contributes knowledge about the characteristics, adaptability and possible commercial potential relative to current commercial varieties in California.

055 - Citrus Rootstock Evaluations

Principal Investigator: Dr. Mikeal Roose, Department of Botany and Plant Sciences, University of California Riverside

The objective of this project is to maintain seed source trees for experimental citrus rootstock selections. A single tree of most selections is planted, with two trees of some of the more promising ones. The selections include hybrids of sweet orange x sour orange; a few zygotic seedlings of various rootstocks identified using molecular markers, and various Phytophthora and salt-tolerant hybrids selected by the USDA breeding program at Indio. Seed is periodically collected from trees in order to establish field trials or to test for disease resistance or other traits. Some trees have also been used as parents in the breeding program. Seeds of several accessions have been distributed to citrus researchers in Florida, Texas, Brazil, and elsewhere for evaluation.

043 - Propagation and Evaluation of Irradiated Citrus Budwood and New Hybrids

Principal Investigator: Dr. Mikeal Roose, Department of Botany and Plant Sciences, University of California, Riverside

The objectives of this project are to identify seedless forms of cultivars that currently perform well in California, and to evaluate new seedless or low-seeded hybrids. The major emphasis is on mandarins, but some work on oranges, grapefruit and lemons is also conducted. Budwood is exposed to irradiation to induce mutations that block seed development, converting a seedy cultivar to a low-seeded one. Trees are propagated from the irradiated buds in the greenhouse at Lindcove REC, planted at Lindcove or at UCR, and evaluated for seediness and other traits. Only a few trees contain suitable mutations. Selected trees are then used as sources of budwood to propagate additional trees for testing at multiple locations. Since the irradiation breeding project was started in 1996, many thousands of trees from budwood irradiation of 36 different varieties or selections have been planted. Evaluation of these resulted in a total of 62 low-seeded selections from 19 varieties, but evaluation of the more recent plantings is still in progress. Selections made from irradiation experiments have now fruited in replicated trials. Most appear quite stable and productive, so the general approach seems to be successful. The University of California released 'Tango', a low-seeded mandarin selection of W. Murcott, in June 2006, and within the past several years 'KinnowLS', 'DaisySL', and 'FairchildLS' mandarins have been released.

033 - Citrus Scion Breeding and Evaluation

Principal Investigator, Dr. Mikeal Roose, Department of Botany and Plant Sciences, University of California Riverside

The objectives of the UCR citrus breeding program are to develop and release new citrus cultivars that are useful in California. The breeding project develops potential new cultivars by hybridization-selection (initially conducted in Riverside) and by mutation breeding to produce seedless forms of existing cultivars. The focus of this Lindcove REC project is on field evaluation of new selections in replicated trials at Lindcove and elsewhere. New selections from the breeding program are propagated in a greenhouse at Lindcove and replicated trials are planted at Lindcove and several other locations in the San Joaquin Valley and southern California. During the next three year period we plan to continue evaluation of existing trees for yield, seed content, other fruit quality traits, tree size and shape, tree health, and other important characters. Additional trees of hybrids and irradiated selections will be propagated for planting in trials at Lindcove and elsewhere. The number of trees to be propagated each year is difficult to predict because breeding is inherently uncertain, but we generally expect to make 3-8 new selections per year. Trees of discarded selections will be removed and replaced with new trees. As promising selections are identified in the replicated trials, registered budwood source trees will be established and new varieties will be released after consulting with University of California and citrus industry organizations.

037 - Citrus Clonal Protection Program

Principal Investigator: Dr. Georgios Vidalakis, Department of Plant Pathology, University of California, Riverside

The California Citrus Clonal Protection Program (CCPP) was established over 50 years ago and today stands as a cooperative program between the University of California, Riverside and the California citrus growers, represented by the California Citrus Research Board, and the California Department of Food and Agriculture (CDFA). The CCPP is responsible for the introduction, disease diagnosis, pathogen elimination, maintenance and distribution of true to type primary citrus propagative material for the needs of the California citrus industry and citrus researchers. The CCPP holds one of only two license permits issued by the USDA-Animal and Plant Health Inspection Services for the legal importation of citrus propagative material into the United States. As such the CCPP is a critical link in the introduction, movement and improvement of citrus not only for California, but has released worldwide over 40 varieties in the last three years alone. The main focus of CCPP remains the detection and elimination of bud-transmitted pathogens from citrus propagative material. This is accomplished with the careful testing of all newly imported varieties and the application of the appropriate therapy method. Citrus propagative material that successfully completes therapy and testing is maintained in CCPP’s Protection Foundation and Foundation-Evaluation Blocks, currently holding over 200 commercially important varieties as CDFA registered trees for budwood distribution. The CCPP distributed over 80,000 buds from its registered trees over the past three years. Registered trees receive periodic disease retesting as well as growth and fruit evaluation. The CCPP distributes evaluation and other citrus information on the web at www.ccpp.ucr.edu.

041 - Field Evaluation of Citrus and Induced Dwarfing

Principal Investigator: Dr. Georgios Vidalakis, Department of Plant Pathology, University of California, Riverside

The concept of dwarfing in citrus is a consideration for the improvement of production in terms of yield (i.e. high density plantings) and quality. Trials with important commercial scions such as Parent navel and Oroblanco grapefruit hybrid, as well as the citrus rootstock varieties Trifoliate and Carrizo, have been established at Lindcove REC in order to evaluate the effects of Transmissible small nuclear RNAs (Tsn-RNAs) on citrus growth, yield, and fruit quality. A high density or close spacing planting pattern has also been evaluated. Dwarfing by Tsn-RNAs is a recent approach (CDFA approved their commercial use in 2001) for the control of vegetative growth. With the limitations imposed on long term plantings as a result of disease, the commercial importance of citrus, and the constant demand for new rootstock and scion varieties, the suggestion of dwarfing and the accompanying feasibility of closely spaced plantings of citrus merits further study.