2013 Annual Report
1a.Objectives (from AD-416):
To determine the inheritance of field resistance to downy mildew, tipburn resistance, sclerotinia resistance, and shelf-life in multiple genetic mapping populations. To identify sources of physiological resistance to sclerotinia. To develop genetically improved lines of lettuce for downy mildew resistance, sclerotinia resistance, tipburn resistance, and shelf-life.
1b.Approach (from AD-416):
The research to be conducted involves developing and analyzing multiple recombinant inbred line populations (RILs) to identify genes and QTL for field resistance to downy mildew, scelertinia resistance, tip burn resistance and extended shelf-life. The RILS wil be evaluated in field and greenhouse experiments, genotyped with molecular marker, analyzed to determine the inheritance traits, and markers suitable for markers assisted selection will also be developed. There is also research to develop improved in vitro and greenhouse methods for sclerotinia resistance.
The agreement was established in support of objective 1 of the parent project. Genetic studies were conducted to determine the inheritance of resistance to race 1 isolates of Verticillium dahliae in six lettuce cultivars. Resistance in five Lactuca accessions was tested in greenhouse experiments to race 1 and race 2 isolates of the pathogen. Fourteen populations from crosses using PIs with partial resistance to race 2 Verticillium dahliae were developed. Field and greenhouse experiments were initiated to evaluate these populations for resistance to race 2 Verticillium dahliae. Fourteen iceberg, seven leaf, and four romaine United States Department of Agriculture or University of California, Davis advanced breeding lines were characterized for yield, horticultural characters, shelf-life of salad and arrival quality, and for resistance to big vein, dieback, Verticillium wilt, lettuce drop, downy mildew, tipburn and pre-mature bolting. Quantitative trait loci (QTL) for salad-cut lettuce shelf-life were identified in two recombinant inbred line populations of lettuce. Linkage maps from the two populations were aligned to identify a single major QTL for salad-cut lettuce shelf-life. Progress was made in developing a molecular marker linked to a major QTL for salad-cut lettuce shelf-life for use in marker assisted breeding.