Location: Vegetable Research
Project Number: 6080-22000-028-000-D
Project Type: In-House Appropriated
Start Date: May 1, 2017
End Date: Apr 30, 2022
1. Develop sensitive and reliable serological and molecular based pathogen detection methods for the emerging and endemic viral diseases of vegetable crops. • Sub-Objective 1.1. Develop a traceable clone of Cucumber green mottle mosaic virus to study the mechanism of seed transmission and to improve seed health assay on watermelon seeds. • Sub-Objective 1.2. Develop traceable clones of pospiviroids (Tomato planta macho viroid and Potato spindle tuber viroid) that can be used to study the mechanism of seed transmission and to develop a reliable seed health assay on tomato. 2. Apply RNAi technology to reduce whitefly vector transmission of plant viruses, including Tomato yellow leaf curl virus in tomato and other viruses in cassava. • Sub-Objective 2.1. Develop dsRNA constructs to evaluate their RNAi effect on whitefly (Bemisia tabaci) as a sprayable insecticide. • Sub-Objective 2.2. Develop transgenic tomato plants with RNAi effect against whitefly as a proof of concept to control whitefly-transmitted viruses. 3. Develop molecular markers associated with host resistance to viral diseases in vegetables and Fusarium wilt on watermelon. • Sub-Objective 3.1. Genotyping-by-sequencing to identify SNPs in association with disease resistance breaking of tomato by the emerging Tomato mottle mosaic virus. • Sub-Objective 3.2 Develop molecular markers associated with fusarium wilt resistance in watermelon. 4. Develop environmentally sustainable disease management strategies against diseases of vegetable crops. • Sub-Objective 4.1. Develop bacterial blight resistant germplasm in Brassica rapa. • Sub-Objective 4.2. Develop an anaerobic soil disinfestation system effective in reduction or elimination of Ralstonia solanacearum in solanaceous crops.
Relative to Objective 1, an infectious clone of Cucumber green mottle mosaic virus will be developed to study the mechanism of seed transmission in watermelon. A sensitive bioassay will be developed to improve the seed health assay on watermelon seeds for CGMMV. Infectious clones of Tomato planta macho viroid and Potato spindle tuber viroid will be developed and used to study the mechanism of seed transmission of pospiviroids on tomato. Sensitive bioassays will be developed to allow a reliable seed health assay on tomato using seedling growout or through mechanical inoculation of seed extract, depending on the mechanism of seed transmission. For Objective 2, based on the results from whitefly genome and transcriptome analysis, double-stranded ribonucleotide acid (dsRNA) constructs will be developed to evaluate the RNA interference (RNAi) effect on whitefly survival through topical spray application on plants. Transgenic tomato plants will be developed to evaluate the RNAi effect against whitefly as a proof of concept to control whitefly-transmitted viruses on crop plants. Under Objective 3, genome sequencing technologies will be used to identify single nucleotide polymorphisms (SNPs) associated with disease resistance breaking of tomato by the emerging Tomato mottle mosaic virus. In other experiments, sequencing will be used to identify SNPs associated with genes that confer resistance against Fusarium oxysporum using populations generated from the USVL246-FR2 breeding line demonstrated to have resistance to Fusarium oxysporum f. sp. niveum (Fon) races 1 and 2. For Objective 4. Using traditional breeding techniques, bacterial blight resistant germplasm in Brassica rapa with a Chinese cabbage-like phenotype, will be advanced through back-crosses and additional crosses to the locally-preferred, genetically-related turnip green cultivars. In separate experiments, an anaerobic soil disinfestation system effective in reducing or eliminating Ralstonia solanacearum in solanaceous crops will be developed. An anaerobic soil disinfestation strategy can be implemented to reduce or eliminate the bacterial wilt pathogen in infested soils.