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ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Research Project #432643

Research Project: Biology, Epidemiology and Management of Vector-Borne Viruses of Sugarbeet and Vegetable Crops

Location: Crop Improvement and Protection Research

2017 Annual Report


Objectives
Objective 1: Identify specific genes associated with Beet necrotic yellow vein virus infection of sugarbeet that contribute to development of rhizomania disease and the ability of the virus to overcome resistance for use as potential targets for induced resistance. This will involve comparisons with other soil-borne pathogens using inhouse funds. Completion within 5 years. Objective 2: Determine environmental and epidemiological factors contributing to the ability of sugarbeet and vegetable viruses to emerge and establish over competing viruses, to provide effective disease management recommendations and prolong the durability of resistance sources. Specifically: 2.A. Determine the effect of variation among Polymyxa betae isolates on prevalence and dominance of soil-borne viruses affecting sugarbeet, including evaluation of virus competitiveness through collaborative studies involving this project using both in-house funds and those of a local collaborator in NP308. Completion within 5 years. 2.B. Assess accumulation of CYSDV in different host plants in relation to transmission and in development of host resistance using both in-house funds and collaboration with ARS Salinas vegetable breeding program (NP301). Completion within 5 years. 2.C. Identification of factors influencing emergence and dominance of existing and new curtoviruses in North America through analysis of competitive virus accumulation in host plants. Research will involve in-house funds, with completion within 3 years. Objective 3: Determine environmental and cultural factors contributing to the ability of viruses to induce disease to facilitate breeding efforts for resistance to soil-borne and insect-transmitted viruses affecting lettuce. Completion of both subobjectives within 5 years using both in-house funds and collaboration with Salinas vegetable project (NP301). 3.A. Develop methods for greenhouse-based evaluation of lettuce for resistance to soilborne tombusviruses through identification of environmental factors influencing disease development, and application of this knowledge to germplasm evaluation using controlled environments. 3.B. Identify sources of tospovirus resistance through evaluation of lettuce and Lactuca germplasm using mechanical transmission and viruliferous thrips under greenhouse conditions, for further development by breeders. Objective 4: Determine biological and ecological relationships among vectors and their host plants, the pathogens they transmit, and the environment, and develop novel intervention and management strategies for control of vector-borne diseases of vegetables, through the use of traditional, molecular biology, and bioinformatics approaches.


Approach
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 for BNYVV transmission to sugarbeet. This is associated with increased presence of resistance breaking forms of BNYVV. Single spore isolates of P. betae will be tested for differences in efficiency of BNYVV transmission and effect of vector isolate on virus competitiveness with virus titer. 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. 2.C. Individual curtoviruses accumulate to higher or lower titers during single and mixed infections, and this varies by host plant. This influences virus dominance in the field. Curtoviruses will be transmitted by beet leafhoppers from single and mixed infections with qPCR used 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. 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. Objective 4: Use a combination of bioinformatics analysis of insects with related applied and molecular entomological approaches to examine how insect vectors respond biologically and biochemically to environmental parameters. This will include but is not limited to the responses of whiteflies and leafhoppers to specific host plants, the presence or absence of plant viruses in host plants, and pesticides applied to host plants. Knowledge gained through these studies will be used to develop novel methods for vector population control through both biotechnology-based and genetics approaches.


Progress Report
This project began in April 2017. It is a bridging project that replaces project 2038-22000-013-00D that expired on April 24, 2017. A new project plan is being developed to address changes in agricultural production within the Pacific West Area. Scientists at ARS in Salinas are preparing clones for use in transformation of plants for induction of resistance against whiteflies as the next step in a multi-year project focused on whitefly control. The approach involves RNA interference, and is a method for specific elimination of the whitefly vector (and not other insects) in vegetable crops and cassava, an important food staple in the developing world. Research toward development of methods for induction of resistance using nontransgenic approaches is also continuing on both tomato and melon, as well as by collaborators in Africa on cassava. Continuing work is focused on establishing infectious clones of a torradovirus isolated from southern California for use in studies on virus host range characterization, insect transmission, and determining the function of virus genes. Tomato necrotic dwarf virus (ToNDV) was first identified in the 1980s from Imperial County, but reemerged in Imperial and Kern Counties, California in 2015. Some isolates of the virus causes severe dwarfing of tomato plants and a dramatic decrease in seed production.


Accomplishments
1. Screening lettuce for tospovirus resistance. Impatiens necrotic spot virus (INSV) is now a serious economic threat to production of lettuce (Lactuca sativa) in coastal California where 75-80 percent of U.S. lettuce is grown; however, no reliable resistance has been identified to date. A system was previously developed by ARS researchers at Salinas, California to test lettuce for resistance to tospoviruses by ongoing propagation of a thrips population on lettuce infected with INSV in a greenhouse. The method was used to evaluate 89 cultivars, breeding lines, and plant introductions of cultivated lettuce, and 57 accessions from related Lactuca species for resistance to INSV. The most resistant lettuce accessions are being advanced to improve resistance in cultivated lettuce. Results will benefit the lettuce industry in the U.S. and throughout the world by identification of new sources of genetic resistance to INSV that can be incorporated into commercial varieties.


Review Publications
Kaur, N., Chen, W., Zheng, Y., Hasegawa, D.K., Ling, K., Fei, Z., Wintermantel, W.M. 2017. Transcriptome analysis of the whitefly, Bemisia tabaci MEAM1 on tomato infected with the crinivirus, Tomato chlorosis virus, identifies a temporal shift in gene expression and differential regulation of novel orphan genes. BMC Genomics. 18:370. doi:10.1186/s12864-017-3751-1.
Strausbaugh, C.A., Eujayl, I.A., Wintermantel, W.M. 2017. Beet curly top virus strains associated with sugar beet in Idaho, Oregon, and a Western U.S. collection. Plant Disease. 101:1373-1382.
Wintermantel, W.M. 2017. Cucurbit yellow stunting disorder virus. In: Keinath, A.P., Wintermantel, W.M., Zitter, T.A., editors. Compendium of Cucurbit Diseases and Pests. 2nd edition. St. Paul, MN: APS Press. p. 123-125.
Wintermantel, W.M. 2017. Squash mosaic virus. In: Keinath, A.P., Wintermantel, W.M., Zitter, T.A., editors. Compendium of Cucurbit Diseases and Pests. 2nd edition. St. Paul, MN: APS Press. p. 135-136.
Wintermantel, W.M. 2017. Tobacco ringspot virus. In: Keinath, A.P., Wintermantel, W.M., Zitter, T.A., editors. Compendium of Cucurbit Diseases and Pests. 2nd edition. St. Paul, MN: APS Press. p. 151-152.
Wintermantel, W.M. 2017. Tomato ring spot virus. In: Keinath, A.P., Wintermantel, W.M., Zitter, T.A., editors. Compendium of Cucurbit Diseases and Pests. 2nd edition. St. Paul, MN: APS Press. p. 152-153.
Okuda, M., Wintermantel, W.M. 2017. Cucurbit chlorotic yellows virus. In: Keinath, A.P., Wintermantel, W.M., Zitter, T.A., editors. Compendium of Cucurbit Diseases and Pests. 2nd edition. St. Paul, MN: APS Press. p. 122-123.
Wintermantel, W.M. 2017. Cucumber leaf spot virus. In: Keinath, A.P., Wintermantel, W.M., Zitter, T.A., editors. Compendium of Cucurbit Diseases and Pests. 2nd edition. St. Paul, MN: APS Press. p. 141-142.
Wintermantel, W.M. 2017. Beet pseudo-yellows virus. In: Keinath, A.P., Wintermantel, W.M., Zitter, T.A., editors. Compendium of Cucurbit Diseases and Pests. 2nd edition. St. Paul, MN: APS Press. p. 126-127.