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ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Research Project #444159

Research Project: Genetic Improvement of Lettuce, Spinach, Celery, Melon, and Related Species

Location: Crop Improvement and Protection Research

Project Number: 2038-21530-003-000-D
Project Type: In-House Appropriated

Start Date: Apr 11, 2023
End Date: Apr 10, 2028

Objective 1: Develop genetic resources and germplasm resistance to key pests and pathogens and abiotic stresses of lettuce, spinach, celery, and melon. Sub-objective 1.A: Breed for resistances to fungal, bacterial, and viral diseases and disorders in lettuce. Sub-objective 1.B: Develop durable resistance to downy mildew in spinach. Sub-objective 1.C: Improve celery for resistance to Fusarium oxysporum f.sp. apii (Foa) races 2 and 4. Sub-objective 1.D: Breed melon for resistance against powdery mildew, virus, and whitefly. Objective 2: Develop new procedures and technologies to evaluate and enhance postharvest quality and shelf life of fresh cut leafy greens, especially lettuce. Objective 3: Improve content and bioavailability of phytonutrients or fiber of leafy vegetables for improved impact on human health nutrition and composition of the gut microbiome. Sub-objective 3.A: Characterize polyphenol and fiber content among lettuce cultivars. Sub-objective 3.B: Breed red spinach for improved nutrient content and disease resistance. Objective 4: Characterize the composition and effects of environment on the microbiota found on leafy vegetables.

Objective 1: Sub-objective 1A: Map major QTLs for resistance to downy mildew using a genome-wide association mapping (GWAS) approach and develop breeding lines with the improved resistance to lettuce drop and downy mildew. Characterize resistance to Fusarium, Verticillium, and Pythium wilts to develop improved lettuce germplasm. Cross corky root-resistant variety ‘Glacier’ and wild species L. serriola to sources of other disease resistance and select for combined resistances to corky root, leafminer, downy mildew, lettuce mosaic virus, tipburn, and horticultural and nutritional traits in different types of lettuce. Characterize resistance to impatiens necrotic spot virus to develop improved lettuce germplasm. Develop controlled environment and molecular assays to characterize tipburn resistance in lettuce. Sub-objective 1B: Breed open-pollinated (OP) spinach with resistance to all prevalent downy mildew races through crosses in isolators, recurrent selection, and replicated field trials. Sub-objective 1C: Develop celery germplasm with resistance to Foa races 2 and 4 through disease assays, selection, and self-pollination. Sub-objective 1D: Breed western U.S. shipper type melon resistant to powdery mildew races 1, 2, 3.5, 5, and S. Identify and characterize resistance in melon to whitefly-transmitted cucurbit chlorotic yellows virus (CCYV). Characterize antixenosis to sweetpotato B biotype whitefly in melon. Objective 2: Fine-map the locus for slow decay of fresh-cut lettuce, map QTLs for limited oxidative browning, and develop lettuce breeding lines with high postharvest quality. Objective 3: Sub-objective 3A: Characterize polyphenol and fiber content among lettuce cultivars to understand genotype x environment interactions and to identify genetically stable high polyphenol cultivars in replicated greenhouse assays. Sub-objective 3B: Improve the betacyanin content, antioxidant capacity, and downy mildew resistance of different types of spinach through crossing, recurrent selection, and field trials. Objective 4: Determine the relationships in the phyllosphere community among leafy vegetables, nearby weeds, and the soil microbiota by isolating genomic materials from the phyllosphere and rhizosphere for sequencing.