TRANSLATIONAL GENOMICS OF ONION FOR PRIORITIZED PEST RESISTANCES
Vegetable Crops Research Unit
2011 Annual Report
1a.Objectives (from AD-416)
Extension: We will expand close working relationships among breeders, extensionists, and growers of major Alliums in the US to evaluate germplasms for prioritized pest resistances and lay the foundation for the long-term translational genomics of the Allium vegetables. Workshops will be held at regional and national Allium meetings.
Research: We will significantly increase the numbers of robust single nucleotide polymorphisms (SNPs) and develop a high through-put genotyping platform for onion. We will tag chromosome regions controlling prioritized disease-resistance traits of onion and transfer these tools to the private sector.
1b.Approach (from AD-416)
Develop a detailed genetic map for onion:
o Identify simple single nucleotide polymorphisms (SNPs) in onion;
o Develop high throughput SNP genotyping platform for onion;
Work with extension professionals to empower growers to complete on-farm evaluations for resistances or tolerances to prioritized diseases and pests; Self-pollinate and testcross selected plants and return seed to the extension-grower collaborators for validation of phenotypes; Deliver validated germplasms to private and public sector breeders; Exploit association genetics to tag grower-selected resistances. Develop workshops for public and private-sector researchers, students, and regional grower and consumer groups for onion to illustrate the usefulness of genomics to solve high-priority research goals.
Specialty Crops Research Initiative.
Field evaluations of onion germplasms from the USDA plant germplasm system were completed in Colorado and New Mexico in order to screen for resistances or tolerances to Iris Yellow Spot Virus (IYSV) and thrips. Although no resistance has been identified, specific accessions performed better over both locations over two years; many of these better performing plants possess fewer epicuticular waxes (semi-glossies). Plants from these better-performing accessions were selected for self-pollination and testcrossing in order to validate tolerances. Flowering plants of onion inbreds B5225B and OH-1 were produced and used to extract ribonucleic acids (RNAs) for synthesis of normalized complementary deoxyribonucleic acid (cDNA) libraries. Sequencing of onion cDNAs from these two inbred populations produced over 3.6 million reads and 1,158 megabasepairs of onion sequence. These cDNA sequences are being evaluated for single nucleotide polymorphisms for genetic mapping. Onion germplasms were evaluated in the field for the semi-glossy phenotype and an F2 family segregating for this foliage type was produced. Over 250 gynogenic haploids extracted from F1 plants from the cross of OH-1 by B5225B were asexually propagated and DNA isolated for mapping of molecular markers. Replicated trials using these asexual propagules were initiated for evaluations of bulb quality. Outreach presentations were made at the National Allium Research Conference, summer meeting of the National Onion Association, and at regional growers’ meetings. A field day for growers and seed producers was held in New Mexico to inspect evaluations for Iris Yellow Spot Virus (IYSV) and thrips. Project is monitored by quarterly conference calls.