Location: Vegetable Crops Research2009 Annual Report
1a. Objectives (from AD-416)
Objective 1: Determine the genetic basis of and initiate selection for carrot, onion, cucumber, and melon quality attributes influencing human nutrition and health, disease resistances, and yield and quality components, and stress tolerance in cucurbits, and perform field performance and quality trials. Objective 2: Utilize current biotechnology to discover and evaluate genetic variation and to map agriculturally important traits in Allium, Cucurbit, and Daucus germplasm, and to develop genetic and breeding stocks. Sub-objective 2.A. Construct genetic maps of nuclear and organellar genomes using candidate genes, SCARs, SSRs, SNPs, transposon insertions, BACs, and cytogenetic stocks. Sub-objective 2.B. Fine map pigment and carbohydrate genes in carrot and onion, resistance genes for nematode in carrot and viruses in cucurbits, and epistasis, yield and quality components in cucumber. Sub-objective 2.C. Perform marker-assisted selection of carrot nematode resistance, onion male sterility, and cucurbit yield and quality. Sub-objective 2.D. Evaluate transgene escape in cucurbits. Sub-objective 2.E. Determine transposon mobility in carrot.
1b. Approach (from AD-416)
The long-term potential for improving a crop is only as great as the breadth of diversity that breeders utilize. Objective 1 targets evaluation and genetic characterization of carrot, onion, cucumber, and melon germplasm for traits important to growers and consumers. Discovery Goal 1 - Identify unique phenotypic variation in germplasm collections and breeding stocks to improve nutritional and processing quality, disease resistance, stress tolerance, and yield of Allium, Cucurbit, and Daucus vegetables, genetically characterize observed variation and initiate genetic incorporation of these phenotypes into elite germplasms. Many biotechnological tools have been developed to improve the efficiency of crop improvement. Objective 2 evaluates and develops these tools of carrot, onion, cucumber, and melon improvement. Identify adequate DNA polymorphisms in elite onion, cucumber, melon, and carrot germplasm to construct genetic maps for marker-facilitated selection of major horticultural traits. Discovery Goal 2.A – Identify adequate DNA polymorphisms in elite onion, cucumber, melon, and carrot germplasm to construct genetic maps for marker-facilitated selection of major horticultural traits. Discovery Goal 2.B – Evaluate variation at candidate genes in pigment and carbohydrate biochemical pathways for mapping in onion, cucurbit, and carrot. Discovery Goal 2.C – Identify and utilize markers to accurately identify desirable genotypes for male sterility restoration in onion, cucurbit yield, and carrot nematode resistance. Discovery Goal 2.D – Appraise the potential benefit(s) that transgenes might confer on transgenic populations using the ELISA test to estimate the degree of viral infection in wild populations and to determine the potential risk of virus gene introgression from commercial transgenic cultivation. Discovery Goal 2.E - Determine if native transposable elements in the carrot genome, such as DcMaster, and introduced ones, such as maize elements Ac and Ds transpose to new chromosomal regions.
3. Progress Report
Germplasm was collected and evaluation of phenotypic and molecular relationships was made of Allium Cucumis, and Daucus germplasm, and reported in Germplasm Resources Information Network (GRIN). Wild carrot from South America and North Africa, and garlic from Uzbekistan was found to be intercrossable with carrot, and garlic, and useful traits were identified. Field evaluation of carrot, onion, and cucumber breeding stocks and experimental hybrids developed by this program was carried out in California, Michigan, Oregon, Washington, and Wisconsin. Identification of Quantitative trail locus (QTL) for melon orange pigments were identified. Genetic markers were developed to identify diverse carrots and garlic, and the locations of a carrot transposable element were mapped. Genomic information was derived from carrot bacterial artificial chromosomes (BACs) to better characterize the carrot genome. Onion families segregating for health-enhancing fructans demonstrated that two major chromosome regions control the accumulation of health-enhancing fructans. Low-pungency onions possess recessive alleles at these two regions, reducing the ability of these onions to accumulate fructans. Evaluation of onion families for male-fertility restoration was completed and linkage to molecular markers assessed. Development of new onion families was initiated for reduced leaf waxiness (associated with tolerance to thrips), dry matter production, and bulb colors. Work continues on the identification of gene conditioning resistance to Zucchini Yellow Mosaic Virus (ZYMV) and the genetic basis of mitochondrial sorting in cucumber. These markers will be used to more efficiently develop lines for commercial production. This will shorten time for hybrid development to reduce development costs and increase grower competitiveness. In cucumber, several F2 populations have been developed for genetic mapping of horticulturally or biologically important genes. Cucumber genomic resources are being developed (whole genome sequencing and transcriptome sequencing). The genetic diversity among USDA collection of African horned cucumber, a relative of cucumber was evaluated with molecular markers. Also, a national wide survey was conducted to identify research priorities in the public sector.
Bartoszewski, G., Gawronski, P., Szklarczyk, M., Verbakel, H., Havey, M.J. 2009. A One-Megabase Physical Map Provides Insights on Gene Organization in the Enormous Mitochondrial Genome of Cucumber. Genome. 52:299-307.