ARS | Publication request: Field evaluation of brassica lines for resistance to bacterial blight in Charleston, South Carolina, 2010

Submitted to: Plant Disease Management Reports
Publication Type: Research Notes
Publication Acceptance Date: January 31, 2011
Publication Date: May 1, 2011
Citation: Keinath, A.P., Farnham, M.W., Wechter, W.P. 2011. Field evaluation of brassica lines for resistance to bacterial blight in Charleston, South Carolina, 2010. Plant Disease Management Reports. 5:V082.

Technical Abstract: Twelve leafy green Brassica entries (including turnip, mustard, and collard greens) were evaluated for response to inoculation with Pseudomonas syringae pv. alisalensis (Psa) in an experiment conducted at the Clemson University Coastal Research and Education Center in Charleston, SC. On 21 September 2010, 40 transplants per plot were set in 2 rows on raised beds spaced 3 feet apart; plants were spaced 6 in. apart within rows. The experimental design was a randomized complete block with four replications. On 14 October 2010, all plants were inoculated by spraying them with a 0.2 OD600 suspension of Psa with a CO2-backpack sprayer. To help establish the pathogen, leaf wetness was maintained by using Senninger low pressure mini-wobbler sprinklers to produce a mist in the evening for 30-60 min each day until harvest. On 27 October 2010, plots were rated visually for percentage leaf surface area with symptoms of bacterial leaf spot using a 0 to 100% scale in 5% increments. On 29 October 2010, all plants were harvested from a 3.3-ft section of the right-hand row in each plot. Leaves were removed from harvested plants and sorted into asymptomatic (healthy) or diseased groups that were weighed separately. Leaves with any symptoms of bacterial blight were considered diseased. Although, bacterial blight developed on all 12 entries, they differed in disease severity. Two cultivars of turnip greens, tendergreen mustard (also known as spinach mustard), and the two cultivars of collard were among the most severely diseased entries. Three of the Plant Introduction (PI) lines (G 30499, PI 418956, and G 30988) were more resistant than all commercial cultivars except kale and Southern Curled Giant mustard. One PI line, a bok choy, was susceptible to bacterial blight. Because of differences in plant size and leaf density, weight of healthy leaves could not be compared across different species. The three resistant PI lines, kale, Top Bunch collard, and Southern Curled Giant mustard were the cultivars with the highest percentage of healthy leaves (by weight); these six cultivars differed significantly from the two cultivars of turnip greens and Tendergreen mustard, which had the lowest percentages of healthy leaves.