Recipient Organization
UNIVERSITY OF CALIFORNIA, RIVERSIDE
(N/A)
RIVERSIDE,CA 92521
Performing Department
Plant Pathology, Riverside
Non Technical Summary
The Vegetable and Strawberry Pathology Program will integrate advancing technologies, unexplored niches, and classical methods across several fronts to improve disease management in these crops. First, we will understand how pathogens in soil are accidentally spread from field to field, and how knowledge of weather conditions important for foliar diseases can be used to reduce fungicide use. Second, we will study how pathogens survive in the soil and how the soil environment could be made more inhospitable to them. Third, we will develop varieties of plants that have natural resistance to pathogens. Fourth, we will develop tools to map patterns of disease so that pesticides can be applied only to needed areas. Finally, we will understand how crop production affects soil health and then develop production systems that sustainably manage diseases of vegetables and strawberry over the long term.
Animal Health Component
50%
Research Effort Categories
Basic
25%
Applied
50%
Developmental
25%
Goals / Objectives
Objective 1 - Disease Epidemiology: For soilborne pathogens, we will determine patterns of their distribution within and among agricultural fields as they relate to factors such as crop and management history. We will next identify mechanisms and dynamics of dispersal of soilborne plant pathogens. Then, we will combine this information toward the development of practices that growers can use to mitigate the movement of soilborne pathogens. For foliar pathogens such as downy mildews, we will first understand how environmental and other conditions influence disease epidemics in the unique desert environment of Southern California. Then, we will adapt existing advisory models and/or develop new models that can be used by practitioners to efficiently time fungicide applications.Objective 2 - Pathogen Biology and Ecology: We will investigate the biology and ecology of pathogens toward the development of improved management strategies for the diseases they cause. For soilborne pathogens, we will identify environmental, soil microbial community, soil physical, management, or other factors that influence disease severity and inoculum survival. We will also seek to understand the population biology of pathogens to identify sources of inoculum, routes of dissemination, and the potential of the pathogen to evolve in response to changing management practices or the deployment of resistant varieties. Objective 3 - Host Resistance and Pathogenicity: We will collaborate with plant breeders to develop cultivars of crops such as strawberry and lettuce with reduced susceptibility to disease. With a focus on soilborne pathogens, we will evaluate germplasm for disease resistance in greenhouse and field studies. We will investigate mechanisms of pathogenicity in greenhouse and lab studies on the ultrastructure of the infection process, and assist in the development of protocols to reduce the time needed to make resistant cultivars available for use.Objective 4 - Remote Sensing and Precision Agriculture: We will develop remote sensing tools that allow efficient detection of agronomic, pathogen, or pest problems. For soilborne pathogens, information obtained from these tools will be combined with actual pathogen levels as described above toward the development of precision agriculture methods that reduce the cost and use of fumigants by implementing management practices only where they are needed and will be effective.Objective 5 - Cropping Systems and Soil Health: We will integrate knowledge and experience gained from the objectives described above toward the development of long-term cropping systems that maximizes economic sustainability and soil health. We will characterize the influence of management practices on the composition of the soil microbial communities, and then seek to understand how these communities affect the ecology of soilborne pathogens. In addition to the above objectives, research for this objective will include investigations of soil amendments and crop rotations for reducing soilborne disease severity.
Project Methods
Objective 1 - Disease Epidemiology: We will investigate the dispersal of soilborne pathogens in multiple stages. First, we will use traditional culture plating assays and quantitative PCR to determine the distribution of important pathogens among fields within major production areas for crops such as strawberry, lettuce, tomato, and onion and garlic. Second, we will identify mechanisms of dispersal of soilborne pathogens and quantify the amount of pathogen inoculum disseminated by each mechanism. Soil will be sampled from field equipment, cars, or workers' boots that have traversed actual production fields with a known inoculum level, and airborne dust emanating from activity within a field will be collected and assayed for pathogen inoculum. Third, information developed from these previous experiments will be used to develop sanitation or other practices that reduce the dispersal of soilborne pathogens.For the downy mildews, we will first evaluate in field trials how existing epidemiology models perform for timing fungicide applications in the desert environment of Southern California. Second, we will investigate the epidemiology of the downy mildew diseases of vegetables such as Brassicas, lettuce, onion, and spinach, and then apply that information to improve existing models and/or develop new models. Third, we will validate and deploy tools implementing the models that can be used by clientele to inform application decisions. Objective 2 - Pathogen Biology and Ecology: Efforts for this objective will include Macrophomina phaseolina of strawberry, but initial efforts will focus on Verticillium dahliae of lettuce, strawberry, and other crops. For Verticillium dahliae, research will seek to understand the ecology and population biology of the pathogen. We will compare the fitness of race 1 and race 2 using various phytopathological and ecological parameters, such as survival of microsclerotia in the soil, pathogenic aggressiveness on hosts of interest, and production of microsclerotia on affected plants. These studies will initially be conducted in the greenhouse, and will utilize field soil obtained from a site in which inoculum of race 2 of V. dahliae has repeatedly been introduced but not successfully established. The second area seeks to understand the broad-scale population biology of V. dahliae. First, unexplored questions in existing data will be examined to determine how population genetic structure using microsatellites relates to race and mating-type structure. Second, a rapid next-generation assay will be developed that simultaneously collects data from numerous loci of several different types of markers, and employed to fill gaps in the data set. Third, multilocus, SNP, and/or genomic nucleotide data will be analyzed to examine the deep scale evolutionary history of V. dahliae. Specific questions addressed by this second area concern origin and source populations, mechanisms of movement and introduction, the evolution of the two races, and the general evolutionary potential of the pathogen. Objective 3 - Host Resistance and Pathogenicity: Work for this objective will initially focus on M. phaseolina of strawberry in two areas: germplasm evaluation and mechanisms of resistance and pathogenicity. Germplasm will be evaluated in fields infested with M. phaseolina, and include assessment of mortality, yield, and extent of pathogen colonization. Investigations of mechanisms of resistance and pathogenicity will consist of understanding the role of abiotic stress on Charcoal rot. To do this, shade structures and individual plot drip irrigation systems will be employed to simulate heat and drought stress within field experiments. This experiment will be performed both in the presence and absence of the pathogen to disentangle the influence of these biotic and abiotic stresses. Plants will be destructively sampled to assess the location and extent of colonization in various tissues using isolation into pure culture, microscopy, or quantitative PCR. Next, based on the results from this field experiment, a more focused evaluation of the important factors will be performed in greenhouse experiments using a wider range of cultivars or germplasm accessions. Then, the knowledge and tools developed from these studies will be applied toward rapid identification of resistant traits and development of commercial cultivars.Objective 4 - Remote Sensing and Precision Agriculture: We will address this objective in two focus areas. The goal of the first area is to improve the efficiency of scouting activities. We will identify sensors, measurements, and platforms that are useful for assessing plant health, and determine if certain detection signals are signatures of pathogen or pest infestation or agronomic problems related to fertility or irrigation. In addition, we will also examine if crop yield or quality can be predicted for the purpose of timing harvests or planning marketing to distributors. Secondly, to develop precision agriculture systems, we will determine the fine-scale distribution of relevant pathogens within a selected number of fields. This distribution will next be related to remote sensing and/or fine-scale yield data to determine the sampling scheme needed to efficiently assay pathogens to the scale required for the precision agriculture platform. Then we will determine which management practices are appropriate to implement against various levels of pathogen inoculum.Objective 5 - Cropping Systems and Soil Health: The four objectives described above are generally mutually exclusive of each other. Each, however, will be integrated toward the broader objective of development of sustainable long-term vegetable and strawberry cropping systems. In contrast to the single-factor approaches described above, the cropping systems objective will compare system profitability, crop yield and quality, the soil microbiota, soil physical properties, and pathogen inoculum dynamics of multi-factor systems over the course of several years. Factors not specifically mentioned above such as soil amendments and crop rotation will be included in this research. A significant part of this objective will be investigating the interaction among these cropping systems with the soil microbial community. Analysis of the soil microbiota will primarily focus on prokaryotes and fungi but may include archaea and non-fungal eukaryotes, and will consist of both taxonomic and putative functional approaches. Areas of focus could include gaining insight into the mechanisms behind the suppression of soilborne pathogens in strawberry production afforded by alternative practices to methyl bromide or why some soilborne disease problems are less damaging in some organic versus conventional vegetable systems. Studies in this area will include identifying traits that are associated with disease severity and yield in many production fields, and in controlled field studies replicated at selected locations. For example, a study in strawberry would characterize the profitability, pathogen dynamics, and soil microbiota dynamics of conventional fumigation versus anaerobic soil disinfestation over the long-term. An integrated study in lettuce would examine the risk of introduction of V. dahliae race 2 into a field in the context of the soil physical and microbial properties and the fitness of race 2 strains.