APS Homepage

Poster: Biology & Disease Mgmt: Genetics of Resistance


Identifying onion cultivars with reduced susceptibility to center rot
J. MAZZONE (1), B. Gugino (2), M. Mansfield (2) (1) The Pennsylvania State University, U.S.A.; (2) The Pennsylvania State University, U.S.A.

Onion growers in Pennsylvania (PA) are continually challenged by losses from center rot disease caused by the bacterial pathogens Pantoea ananatis and P. agglomerans. The objective of this research is to identify onion cultivars that are less susceptible to center rot than the commercial standard cv. Candy but still meet the criteria of the PA Simply Sweet Onion Marketing Program. Thirteen onion cultivars were evaluated between 2015 and 2016 for center rot susceptibility and select horticultural characteristics, including neck and bulb diameter. Cultivars were arranged in a randomized complete block design and plots were split by proximity to inoculated plants. Two onion leaves of select plants were inoculated with a mixture of P. ananatis and P. agglomerans isolates. At harvest, onions were graded by size, marketability and disease incidence. Sub-samples of asymptomatic onions were evaluated for soluble solids, pungency and postharvest disease incidence. In 2015, six cultivars had marketable yields comparable to cv. Candy. Center rot incidence significantly differed between cultivars at harvest (P=0.002) but not after 3-months in storage (P=0.241). A positive, linear relationship was observed between late season onion neck diameter and center rot incidence. All cultivars met the minimum soluble solids and pungency criteria for the marketing program. Evaluations in 2016 will further investigate cultivars that show promise in sweet onion production.