Location: Crop Improvement and Protection Research
Project Number: 2038-22000-013-00
Start Date: Apr 25, 2012
End Date: Apr 24, 2017
Objective 1: Some defense genes will be common to general sugarbeet or plant defense against pathogens. Determine similarities and differences among pathogens for gene expression between infected and pathogen free host plants based on results of studies currently concluding. Results will be compared with others including BNYVV and other pathogens through parallel studies. Objective 2: 2.A. Isolates of the plasmodiophorid vector of BNYVV, Polymyxa betae, differ in their ability to transmit BNYVV to sugarbeet and this is associated with increased presence of resistance-breaking forms of BNYVV in sugarbeet production. Single spore isolates of P. betae will be tested for ability to transmit BNYVV to examine transmission efficiency and effect of vector isolate on virus competitiveness with virus titer determined by ELISA or qRT-PCR. 2.B. Resistance from the exotic melon (Cucumis melo) accession PI 313970 can enhance resistance to CYSDV in cultivated melon, and provide high levels of resistance when combined with resistance source TGR-1551. Exotic melon accessions will be evaluated in replicated field plantings and studies will examine transmission efficiency of CYSDV from resistant and susceptible melons in comparison with virus concentration using either qRT-PCR or ELISA. 2.C. Individual curtoviruses accumulate to higher or lower titers during single and mixed infections, and this varies by host plant, and this influences virus dominance in the field. Curtoviruses will be transmitted by beet leafhoppers from single and mixed infections and qPCR for virus titer determination. If needed Agro-based delivery of virus isolates to specific hosts, or leafhopper membrane feeding studies could be used for virus delivery. 2.D. The proposed studies will elucidate grapevine leafroll transmission by two mealybug species and explore options for monitoring and management of mealybugs. Greenhouse studies involving single-virus isolates and each mealybug species will be conducted to determine efficiency for transmission of grapevine leafroll associated viruses isolated from California vineyards using viruliferous mealybugs. RT-PCR or ELISA will be used to detect virus. Objective 3: 3.A. Long-day or high temperature treatment will induce development of tombusvirus symptoms on susceptible lettuce and can be used for selecting resistant and susceptible varieties. Growth chamber experiments will be used to determine optimal environmental conditions (light, temp, soil moisture etc.) for tombusvirus infection of lettuce using mechanical transmission experiments. Chamber and soil moisture and nutrition conditions can be modified as needed. 3.B. Resistance to Impatiens necrotic spot virus (INSV) and Tomato spotted wilt virus (TSWV)exists in wild or cultivated Lactuca germplasm and can be identified through greenhouse evaluation. Transmission of INSV and TSWV to Lactuca germplasm sources will be conducted using thrips vectors in the greenhouse. Virus detection will be performed using standard ELISA. If necessary, virus can be mechanically transmitted directly to lettuce from select hosts.