Location: Vegetable Crops Research2010 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 2009, seed of 106 plant introductions (PI), experimental lines, and commercial cultivars of onion were sown in Las Cruces, NM. Plants were spaced 7.5cm apart within the row & two rows were planted per plot. On the first & last bed of the study & at the front and back borders of the study, Iris Yellow Spot Virus (IYSV)-infected bulbs, from the previous year IYSV evaluation study, were placed to ensure IYSV inoculum in the field. On each third bed, IYSV-susceptible breeding lines were sown in October 2008 to act as disease spreader rows. The field was designed such that onion thrips would acquire IYSV from the infected bulbs, live on these bulbs until scape formation, then move to autumn-sown plants, & once these plants matured then move to the test plants. At each move, thrips would transfer IYSV to those new plants. Onion plants were grown using standard cultural practices for growing onions in southern New Mexico except that chemical sprays were not applied for controlling onion thrips levels. At 12, 14, 16, and 20 weeks post planting, entries were evaluated for the number of thrips per plant. At 16 weeks, entries were evaluated for leaf color & leaf waxiness. At 16, 20, and 24 weeks, entries were evaluated for leaf axil pattern and Iris yellow spot (IYS) disease severity. When 80% of the plants had matured, all bulbs from the plot were harvested. From within a plot, plants that exhibited few IYS foliar disease symptoms were selected and kept separate from other bulbs harvested from the plot. At 14 weeks, PIs 248753, 248754, 274780, and 288272 averaged less than three thrips per plant, less than most entries tested and less than the average number of thrips per plant for all other entries. These accessions produced dark green leaves that had a moderate amount of wax. At this time, there were very few differences in thrips number per plant among the commercial cultivars and experimental breeding lines tested. OLYS 05N5 exhibited fewer thrips per plant than several entries. By 16 weeks, there were no differences among entries for thrips number per plant. Seventeen accessions were rated as having light to dark green leaf color, three were rated as having semi-glossy to glossy leaves, and one possessed an open leaf axil pattern. PIs 239633 and 289689 possessed glossy foliage that was dark green in color. PIs 258956, 546188, and 546192 possessed semi-glossy foliage that was dark green in color. Two entries, New Mexico State University (NMSU) 07-30-2 and 07-54-1, were rated as having semi-glossy to glossy leaves. There were very few differences in leaf axil pattern among the entries tested in this group. At 20 weeks, PIs 239633, 264320, 321385, 546100, 546115, 546188, and 546192 exhibited less severe IYS symptoms than other accessions. Four weeks later, IYS symptoms became more severe on plants of these accessions, however; plants of PIs 546115 and 546192 exhibited less severe symptoms than most other accessions that had not matured by this time. At each rating time, there were no differences in IYS disease severity and incidence among the commercial cultivars and experimental breeding lines tested. Project is monitored by conference calls.