Determining Redundancy of Current and Collected ‘White Grano' Onion Accessions

The U.S. National Plant Germplasm System has a mission to efficiently maintain a collection of germplasm that is representative and genetically diverse. Reducing genetically-duplicate accessions and adding new and different germplasm to the collection will maximize genetic diversity in the collection. This study was conducted to determine redundancies in the current ‘White Grano' onion (Allium cepa L.) germplasm in the U.S. collection. Some accessions appeared to be duplicates as indicated by their similar cultivar names. Another objective of this study was to evaluate recently-collected ‘White Grano' germplasm to determine if there are duplications among them, and between them and the current ‘White Grano' accessions in the collection. Eight similarly-named ‘White Grano' accessions and collected cultivars were seeded in October of 2007 and in September of 2008. This group of cultivars consisted of four accessions that were already a part of the germplasm collection, and four newly-collected ‘White Grano' cultivars proposed to be added to the collection. Plants from each accession were measured for 18 different morphological characters once the plants from the entries neared maturity. Characters measured included bolting percentage, sheath length and diameter, plant and leaf height, leaf width and thickness, and time when 20% of plants in the plot had reached tops down (20% tops down), 50% tops down, and 80% tops down. At the time of 80% tops down, the bulbs were harvested and the harvest date, pink root disease severity, and bulb number, height and diameter were measured. Two weeks after harvest, average bulb weight, bulb firmness, and the percentage of bulbs with a single growing point were measured. Two ‘White Grano' accessions in the current collection may be removed, as they were determined to be duplicates of other accessions. One newly-collected ‘White Grano' cultivar was found to be different from the accessions already in the collection and may add diversity to the collection. The characters among this group, that were most discriminating, were average bulb weight, percent single centers, bulb height and diameter, shape index, and leaf width and thickness. Characters, that did not discriminate among these accessions, were sheath length and diameter, uniformity of maturity, and plant and leaf height.