Project Number: 2034-22000-014-000-D
Project Type: In-House Appropriated
Start Date: Feb 15, 2022
End Date: Feb 14, 2027
Grapes and citrus are major crops in California with an estimated value of $8.7 billion per year. Inputs for protection against pathogens and insect pests can be significant, and often environmentally friendly control strategies are lacking. To address the plant disease management challenges confronted by grape and citrus producers in California, research will focus on the following four objectives and associated sub-objectives. Objective 1: Create novel grapevine and citrus pathogen identification and disease diagnosis methods. Subobjective 1A: Develop novel species identification techniques for Xylella fastidiosa (Xf) and fungal pathogens of grapevines including utilizing FAME profiling and phenotype microarrays. Subobjective 1B: Improve diagnostics of citrus pathogens through field deployable technologies such as isothermal amplification, robotics, and artificial intelligence. Subobjective 1C: Develop sensitive and accurate detection systems for grape and citrus pathogens using genomic information. Objective 2: Elucidate vector feeding and movement behaviors associated with transmission and spread of Xylella fastidiosa. Subobjective 2A: Compare vector probing behaviors of blue-green sharpshooter (BGSS), with or without Xf, on Pierce’s disease (PD)-resistant or -susceptible grapevines. Subobjective 2B: Develop an electropenetrography (EPG)-based Resistance Index (EPG-RI) to rapidly detect grapevine resistance to Xf inoculation behaviors of vectors. Subobjective 2C: Determine the role of glassy-winged sharpshooter (GWSS) nymphs in spreading Xf within vineyards. Subobjective 2D: Develop a flexible individual-based model to evaluate implications of results from studies conducted during completion of this project on pathogen spread. Objective 3: Develop vibrational control methods for grapevine pests for integration into vineyard management practices. Subobjective 3A: Evaluate female BGSS re-mating receptivity and communication. Subobjective 3B: Determine efficacy of natural tremulatory signals in disrupting mating of the BGSS. Subobjective 3C: Assess BGSS male attractiveness to playback of female vibrational signals. Subobjective 3D: Develop methods for transmission of GWSS and BGSS disruptive signals to crops and ground vegetation. Objective 4: Develop sustainable management tactics for pests and diseases of grapevine and citrus. Subobjective 4A: Develop formulations to improve the use of region-specific biological control strains of Trichoderma spp. as a disease management tool for combating bacterial and fungal diseases of grapevines. Subobjective 4B: Determine susceptibility of vine mealybug (VMB) to soil-applied imidacloprid. Subobjective 4C: Target bacterial endosymbionts for control of VMB. Subobjective 4D: Evaluate sub-lethal effects of soil-applied imidacloprid on GWSS fecundity, survival, and movement behavior. Subobjective 4E: Determine distribution and genetic diversity of citrus tristeza virus (CTV) in citrus in California and assess the environmental/economic impact for future deployment of genetically-engineered (GE)-CTV.
The approach is to synergistically exploit weak links between main components of grapevine and citrus pathosystem (pathogen, vector, plant) and insect pests to induce an unstable or neutral interaction that can lead to disruption of destructive processes affecting grape and citrus production. First, disease management requires accurate, sensitive, and cost-effective diagnostic tests to identify causal agents. The most recent genomic information will be used to improve pathogen detection methods that are based on DNA sequences, whereas studies of pathogen phenotypes will lead to development of novel complimentary diagnostic methods. Second, developing plant disease management strategies requires a fundamental understanding of pathogen spread. Mathematical models will be used to evaluate the role of environmental factors on pathogen spread and to simulate management approaches. Experiments will compare insect vector feeding behaviors on resistant and susceptible plants and evaluate the role of juvenile stages in pathogen spread. Third, management of insect-transmitted pathogens requires novel sustainable methods for suppressing vector population growth. Methods to disrupt mating by interfering with insect vector behaviors will be developed. A final objective will assess current control methods to minimize risk of insecticide resistance, develop novel molecular technology targeting vector endosymbionts, identify biological control agents of fungal cankers, and evaluate safety and efficacy of genetically-engineered viruses to manage citrus diseases. The research will benefit grape and citrus growers by addressing current needs and developing novel technology to meet the demand for sustainable farming practices.