Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/29/2012
Publication Date: 1/10/2013
Citation: Wechter, W.P., Keinath, A.P., McMillan, M.L., Smith, P., Farnham, M.W. 2013. Expression of leaf blight resistance in Brassica leafy greens under field conditions and inheritance of resistance in a Brassica juncea source. Plant Disease. 97:131-137. Interpretive Summary: Numerous occurrences of bacterial blight on leafy Brassica vegetables, including turnip and mustard greens, collard, and kale, have been reported in several states that produce these crops, causing millions of dollars in losses the last 10 years. In this study, we tested four Plant Introductions (PI) of mustard and turnip greens, previously identified by our group as having resistance to this disease, in field trials under disease inducing conditions over a 2-year period. Three of these PI were found to outperform, both in resistance and healthy leaf yield, all but one commercially planted mustard and one turnip green cultivars. In addition, we conducted inheritance of resistance studies and determined that resistance to bacterial blight is likely controlled by a single, recessive gene. These three PIs may be valuable sources of resistance to bacterial blight to be used in breeding improved varieties of Brassica leafy greens.
Technical Abstract: Brassica leafy greens are one of the most economically important vegetable commodities grown in the southeastern United States, and more than 28,000 metric tons of these crops are harvested in the U.S. annually. Collards and kale (Brassica oleracea L.), mustard greens (Brassica juncea L.) and turnip greens (Brassica rapa L.) are the most commonly planted members of the Brassica leafy greens group. In the last 10 years, numerous occurrences of bacterial blight on these leafy vegetables have been reported in several states. One of the pathogens responsible for this blight is designated Pseudomonas cannabina pv. alisalensis (Pca). Two B. rapa (G30710 and G30499) and two B. juncea (PI418956 and G30988) plant introductions (PI) that exhibited moderate to high levels of resistance to this pathogen in greenhouse studies were tested for field resistance in comparison to eight commercial cultivar representatives of turnip greens, mustard greens, collard and kale. The two B. juncea PI and one of the B. rapa PI (G30499) were found to have significantly less disease than all tested cultivars except Southern Giant Curled mustard green (B. juncea) and Blue Knight kale (B. oleracea). Inheritance of resistance studies performed with populations derived from the resistant G30988 and two susceptible PI indicate that genetic control of resistance appears to be a single recessive gene.