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United States Department of Agriculture

Agricultural Research Service


Location: Vegetable Crops Research

2011 Annual Report

1a. Objectives (from AD-416)
We will expand close working relationships among breeders, extensionists, and growers of major Alliums in the U.S. to evaluate germplasms for prioritized pest resistances (thrips and Iris Yellow Spot Virus) and lay the foundation for the long-term translational genomics of the Allium vegetables. Workshops will be held at regional onion meetings. We will evaluate in the field onion populations for resistance or tolerance to thrips and Iris Yellow Spot Virus. Resistance or tolerant germplasms will be released to the onion breeders in the public and private sectors.

1b. Approach (from AD-416)
Work with extension professionals to empower growers to complete on-farm evaluations for resistances or tolerances to thrips and Iris Yellow Spot Virus. Self-pollinate and testcross selected plants and return seed for validation of phenotypes; Deliver validated germplasms to private and public sector breeders; 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.

3. Progress Report
In order to screen for resistance or tolerance to Iris Yellow Spot Virus (IYSV), infected bulbs from the previous year were placed in the borders of the evaluation field. At the same time, IYSV-susceptible breeding lines were sown as disease spreader rows. The field was designed such that thrips would acquire IYSV from the infected bulbs, move to the IYSV-susceptible breeding lines, and as these plants matured they would move to the evaluation plots. At 12, 16, and 20 weeks post transplanting or seeding, entries were evaluated for the number of thrips per plant. At 16 weeks, entries were evaluated for leaf color, leaf waxiness, and leaf axil pattern. At 16 and 20 weeks, entries were evaluated for IYSV severity. When more than 80% of the plants had matured, all bulbs from the plot were harvested, counted, weighted, and graded for market classes (colossal, jumbo, medium, and smaller). Thirteen accessions exhibited lower number of thrips per plant. In agreement with previous evaluations, Plant Introduction (PIs) 248753, 248754, 274780, and 288272 exhibited lower number of thrips. Twelve accessions were rated as having light to dark green leaf color, three were rated as having semi-glossy to glossy leaves, and plants of PI 391509 exhibited an open leaf axil pattern. Plants of PI 165498, 258956, and 264320 exhibited semi-glossy foliage that was dark green in color. For commercial cultivars and experimental breeding lines, most entries had leaves that were light to dark green in color. Plants of New Mexico State University (NMSU) 07-54-1 had glossy leaves while 39 entries had semi-glossy leaves. There were very few differences in leaf axil pattern among the entries tested in this group. IYS disease symptoms were more severe this year than the previous year. At 16 weeks, plants of PIs 249899, 264648, 288073, 288903, and 391509 exhibited less severe IYS symptoms. However due to high disease severity, no plants from the PIs were selected as potentially tolerant to IYSV. Seven plants that exhibited lower IYS disease symptoms were selected and are being self-pollinated in hopes of finding progeny that possess a higher level of IYS tolerance. Project was monitored by quarterly conference calls.

4. Accomplishments

Last Modified: 05/23/2017
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