ARS | Publication request: GENETIC ANALYSES OF SEED YIELD IN ONION

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 4, 2001
Publication Date: N/A

Interpretive Summary: In the USA, commercial production of onion is primarily based on hybrid cultivars. Most onion hybrids are from three-way crosses, meaning that the female parent is a hybrid and is crossed with an unrelated male. However the development of two-way onion hybrids is difficult due to poor seed yields of inbred female parents. Two-way hybrids are desirable because of increased uniformity and less time spent in development. The seed yield of onion is affected by inbreeding depression and the seed-production environment. We crossed among seven inbred lines of onion and measured the seed yield of the hybrids. Combinations of relatively high-by-high seed-yielding inbred parents were not always the best combinations; combinations of medium-by-medium or medium-by-high seed yielders also produced good F1 seed yielders. We also observed that the seed yields of randomly selected bulbs were not correlatedwith their progenies, indicating that the relative seed yield of parental plants cannot be used to predict the seed yield of their offspring. This information will be of use to hybrid-onion seed produces and onion breeders.

Technical Abstract: The development of two-way onion (Allium cepa L.) hybrids is difficult due to poor seed yields of inbred female parents. The seed yield of onion is affected by inbreeding depression and the seed-production environment. A standard diallel was used to determine combining abilities for seed yield among seven inbred lines. Males and hybrids differed significantly (p<0.05) for seed yields. Combinations of relatively high-by-high seed-yielding inbred parents were not always the best combinations; combinations of medium-by-medium or medium-by-high seed yielders also produced good F1 seed yielders. For seven inbred lines, significant correlations (p<0.05) were observed between mean seed yield per bulb and scape height. Parent-offspring regressions revealed no significant relationship between the seed yields of randomly selected, open-pollinated bulbs and their S1 families. These results indicate that the relative seed yield of individual bulbs after self pollination cannot be used to predict the seed yield of progeny families. However, the seed yield of inbred lines of onion may reflect the potential seed yield of hybrid male-sterile lines.