Location: Vegetable Research
2023 Annual Report
Objectives
1. Phenotype genetic populations and germplasm and utilize genetic and genomic methodologies to identify gene loci associated with biotic and abiotic stresses, or with horticultural traits in watermelon, broccoli, and leafy Brassicas.
1.A. Evaluate and identify germplasm sources and gene loci useful for improving watermelon cultivars for resistance to the emerging virulent race 3 of Fusarium wilt.
1.B. Optimize light-emitting diode (LED) illumination spectrum for growth and development of collard plants and select genotypes rich in phytonutrients and suitable for cultivation in controlled environment agriculture (CEA) production systems.
2. Use marker assisted selection (MAS) and/or genomic selection (GS) approaches to develop and release watermelon, broccoli, and leafy Brassica germplasm with improved biotic and abiotic stress tolerance, combined with desirable horticultural traits.
2.A. Breed and release small-seeded watermelon lines with desirable fruit qualities and improved resistance to Fusarium oxysporum sp. niveum (Fon) Fon race 1 and to the common aphid-transmitted potyviruses papaya ringspot virus (PRSV) and zucchini yellow mosaic virus (ZYMV).
2.B. Use GS approach to improve Fon race 2-resistance in watermelon cultivars.
2.C. Use GS approach to improve powdery mildew-resistance in watermelon cultivars.
2.D. Use GS approach to improve heat tolerance in broccoli germplasm.
Approach
Germplasm collections will be evaluated for resistance to the emerging virulent race 3 of Fusarium wilt. Marker assisted selection (MAS) will be employed to pyramid qualitative traits of resistance to Fusarium wilt race 1 and potyviruses, while “genomic selection (GS)” approaches will be used to improve watermelon cultivars with complex traits of resistance to Fusarium wilt race 2 and powdery mildew. This project has devoted efforts to elucidate gene loci and to breed for broccoli lines with improved tolerance to high-temperature stress. As with watermelon, GS methods will be employed to uncover all or most gene loci, including those with minor or major effects in conferring heat tolerance and production of high-quality mature broccoli heads. A different objective of this project focuses on evaluating and selecting for collard genotypes suitable for cultivation in controlled environment agriculture (CEA) production systems, used as an alternative to meet the increased demand for local growing food crops. Here, collard genotypes rich in phytochemicals will be selected and bred for cultivation in CEA. Successful completion of this project objectives will contribute to the long-term improvement of disease resistance and abiotic tolerance in cucurbit and brassica crops. It will also greatly benefit seed company breeders, growers, and consumers of these important vegetable crops.
Progress Report
New project plan (6080-22000-020-000D) started 4/11/2022. Research has been initiated and is on track to fully complete all projected 12-month milestones. This project is related to the old, terminated project: 6080-22000-019-000D, Genomics and Genetic Improvement of Disease Resistance and Horticultural Characteristics of Watermelon, Broccoli, and Leafy Brassicas. Please see annual progress report for the related project 6080-22000-019-000D.
ARS researchers in Charleston, South Carolina, released a zucchini yellow mosaic virus (ZYMV) and papaya ringspot virus (PRSV)-resistant watermelon line “USVL-380. They also co-released a plant variety protected (PVP)- rootstock line “Carolina Strongback” having resistance to fusarium wilt and root-knot nematode and that is useful for grafting watermelon cultivars. Disease resistant watermelon and heat tolerant lines were provided to several national and international seed companies and universities through material transfer agreements (MTA). We have conducted genomic and genetic analyses studies, and in collaboration with the bioinformatics team at the Boyce Thompson Institute (Cornell University) we sequenced and assembled the genome of the principle American watermelon cultivar “Charleston Gray” and re-sequenced 1300 United States Plant Introductions (PIs) of the USDA-ARS watermelon (Citrullus spp.) germplasm collection. Using advanced genomic approaches, we were able to identify gene loci associated with cold tolerance, downy mildew, and powdery mildew resistance in watermelon. We conducted genetic analysis studies and identified quantitative trait loci (QTL) associated with resistance to Fusarium wilt races 1 and 2 of watermelon, papaya ringspot virus (PRSV) and Zucchini yellow mosaic virus (ZYMV) of watermelon. We have developed and released a self-compatible green sprouting broccoli cultivar ‘HiTest’ that yields seed with high levels of the phytonutrient Glucoraphanin which is known to have health benefits. New research project continuing in the new five-year project plan (6080-22000-020-000D; 2023-2028) to provide stakeholders with genomic and genetic tools and germplasm useful for enhancing biotic and abiotic stress tolerance in vegetable crops.
The process to hire a new SY to fill the vacant Research geneticist position to work on Brassica crops has been initiated.
Accomplishments
