Project Number: 5348-21000-026-03
Project Type: Specific Cooperative Agreement

Start Date: Sep 17, 2007
End Date: Aug 31, 2009

Objective:
The objective of this project is to evaluate newly-acquired, short-day onion germplasm and to compare that germplasm with current accessions in the collection to determine if including that germplasm in the collection would result in redundancy. In addition, this project will evaluate short-day accessions in the collection that appear to have similar cultivar names to determine if some accessions are redundant.

Approach:
Sixty-three Allium cepa accessions and collected germplasm lines will be sown directly into fields during October in Las Cruces, NM. Each entry will have four replications. For each plot, the date of the first top down, the date of 80% tops down and the date of 100% tops down will be recorded. Prior to harvest, the number of seedstalks per plot will be counted and the bolting percentage will be calculated for each plot. Once all of the tops have fallen in a single plot, all bulbs in the plot will be harvested. The root system of 20 bulbs per plot will be rated for the severity of pink root disease (Phoma terrestris, causal agent), and basal plates will be rated for the severity of fusarium basal rot (causal agent, Fusarium oxysporum f. sp. cepae. After curing, the total bulb weight per plot, average bulb weight, firmness, number of growing points for each bulb and the percentage of single centered bulbs per plot will be measuerd. The study will be repeated for a second year to observe yearly differences. Seeds of each accession will be sown in Pullman, WA for DNA extraction. Twelve plants from eight accessions will be selected for within-accession diversity analysis. Additionally, samples from 12 plants from each accession will be bulked and analyzed for among-accession diversity analysis. Phylogenetic relationships will be displayed graphically using NTSys-pc software. The genome of Allium cepa is rather large (~16,000 Mbp), which makes conventional amplified fragment length polymorphism (AFLP) analysis difficult. However, AFLP using extra selective nucleotides in the final selective amplification has provided good results (Volk et al., 2004). In addition, we have used sequence related amplified polymorhpism (SRAP) markers (Li and Quiros, 2001) on Allium species with good results. Microsatellites are also available. A combination of these marker types will be used in the analysis to ensure success. A comparison of diversity in agronomic characteristics will be compared to molecular genetic diversity by diversity matrix comparison using Gowers coefficent and a molecular distance coefficient, respectively. Field and molecular genetic data will be used to make recommendations to the onion curator and to the Root and Bulb Vegetable Crop Germplasm Committee regarding what material from the recently collected short-day onion germplasm is to be included in or withheld from the collection. Documents SCA with New Mexico State. Formerly 5348-21000-020-00D (May 2008).