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ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Research Project #440199

Research Project: Lettuce Breeding and Genetics (2021)

Location: Crop Improvement and Protection Research

Project Number: 2038-21530-002-035-T
Project Type: Trust Fund Cooperative Agreement

Start Date: Apr 1, 2021
End Date: Mar 31, 2022

Objective:
Develop landmark cultivars, advanced breeding lines, information, and tools for use by other breeders, scientists, producers and growers. Problems facing the lettuce industry will be addressed using genetic approaches that are suited to coastal, desert, and interior valley locations, to the various types of lettuce, and to the demands of different production and marketing approaches.

Approach:
To characterize resistance to Verticillium wilt Races 1 and 2 and develop improved lettuce germplasm, we will evaluate germplasm in Race 1-infested and disease-free field experiments, screen with the Vr1-linked molecular marker, and evaluate resistance to Race 2 in growth room and greenhouse experiments. We will develop romaine and iceberg breeding lines with improved lettuce drop resistance for Salinas Valley using Sclerotinia-infested field experiments. To develop Fusarium wilt-resistant lines and combine with Verticillium wilt resistance, we will evaluate germplasm in Verticillium Race 1-infested field experiments and Fusarium-infected greenhouse tests. We will combine lettuce dieback resistance and improved shelf life for romaine and leaf type grown in Salinas Valley by testing F2 to F4 generations and developing new early generations. To develop downy mildew polygenic resistance in romaine, iceberg, and leaf type grown in Salinas Valley we are testing 500 lettuce accessions for resistance and using genome wide association studies to identify loci associated with field resistance. We will develop bacterial leaf spot R-gene and polygenic resistance in baby leaf grown in Salinas Valley by evaluating 500 lettuce accessions for their resistance to five strains of Xanthomonas hortorum pv. vitians (the pathogen causing BLS). To develop multiple lettuce types combining resistance to leafminer with resistance to other diseases, low tipburn incidence, high nutritional value, and good horticultural traits we will evaluate germplasm in field experiments with high leafminer and corky root pressure. We will develop romaine breeding lines with reduced incidence of tipburn by evaluating breeding lines with romaine check cultivars for tipburn incidence, yield and horticultural quality in field experiments. To improve shelf-life of processed lettuce and spring mix grown in Salinas Valley we have developed molecular markers for marker-assisted selection (MAS) and 500 lettuce accessions will be tested for postharvest discoloration. We will develop lettuce germplasm resistant to Impatiens necrotic spot virus in replicated field experiments and greenhouse experiments using manual inoculation and viruliferous thrips transmission. To improve the nutritional value of leaf, romaine, and iceberg lettuce types the nutritional values of crisphead, leaf, and romaine breeding lines will be determined in replicated field experiments. We will develop tools to evaluate germplasm resistance to Pythium by testing a previously reported greenhouse screening method.