Single-centered and Super Colossal Bulbs from Yellow Onion Cultivars.

Onion (Allium cepa) cultivars for commercial production in eastern Oregon and southwestern Idaho are evaluated annually in replicated yield trials conducted at the Malheur Experiment Station, Oregon State University, Ontario. Market demand has progressively called for larger bulb size and bulbs with single centers. At harvest onions were evaluated for maturity, number of bolters, and single centeredness. Cultivars showed a wide range of bulbs with only one growing point or "bullet" single centers, ranging from 1% to 57% in 2000, from 7% to 70% in 2001, and from 1% to 74% in 2002. The percentages of bulbs functionally single-centered for processing uses ranged from 18% to 88% in 2000, from 24.7% to 91.3% in 2001, and from 14.4% to 92% in 2002. Bulb yield and market grade were evaluated out of storage. Marketable yield after 4 months of storage varied significantly by cultivar from 643 to 1196 cwt/acre (72.1 to 134.1 Mg·ha^-1) in 2000, from 538 to 980 cwt/acre (60.3 to 109.8 Mg·ha^-1) in 2001, and from 583 to 1119 cwt/acre (65.3 to 125.4 Mg·ha^-1) in 2002. Averaging over cultivars, super colossal bulb size averaged 26%, 14%, and 10% in 2000, 2001, and 2002, respectively. [ABSTRACT FROM AUTHOR]