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Title: Response to oxalic acid as a resistance assay for Sclerotinia minor in peanut

Author
item Bennett, Rebecca
item PAYTON, MARK - Oklahoma State University
item Chamberlin, Kelly

Submitted to: Peanut Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2015
Publication Date: 7/2/2015
Publication URL: http://handle.nal.usda.gov/10113/61761
Citation: Bennett, R.S., Payton, M.E., Chamberlin, K.D. 2015. Response to oxalic acid as a resistance assay for Sclerotinia minor in peanut. Peanut Science. 42(1):56-64.

Interpretive Summary: Rapid and accurate methods for screening peanut breeding lines for resistance to Sclerotinia blight, caused by the soil-inhabiting fungus, Sclerotinia minor, would speed up progress in developing resistant peanuts. Plant response to oxalic acid has been used to screen beans and soybeans for resistance to white mold, a disease caused by a fungus closely related to S. minor. We evaluated the response of detached stems of six runner- and seven Spanish-type peanuts, which were placed in varying concentrations of oxalic acid. Stems of the susceptible runner cultivars showed the most severe wilt symptoms, but few differences in wilting were found among the Spanish peanuts. More differences in stem discoloration were observed among the Spanish than the runner peanuts, but length of discoloration did not appear to be correlated with resistance. Oxalic acid appears to have some potential as a resistance assay for Sclerotinia blight in runner peanuts, but may be of limited use for screening Spanish peanuts. These results inform researchers trying to develop and improve existing methods for measuring Sclerotinia blight resistance in peanut breeding lines.

Technical Abstract: Response to oxalic acid was evaluated as a potential assay for screening peanut breeding lines for resistance to Sclerotinia blight caused by Sclerotinia minor. Detached stems of seven Spanish- and six runner-type peanut cultivars and advanced breeding lines, varying in resistance to Sclerotinia blight, were placed in 0, 10, and 50 mM oxalic acid. Wilting and stem discoloration were rated 12, 18, and 24 hrs after immersion. Wilting and stem discoloration were not observed on stems placed in water (0 mM), but differences among entries were observed for some of the time intervals at the 10 and 50 mM oxalic acid solutions. Susceptible runner cultivars exhibited the most severe wilt symptoms, but few differences in wilting were found among the Spanish entries. More differences in stem discoloration were observed among the Spanish peanuts than the runner entries, but length of discoloration did not appear to be correlated with resistance. Oxalic acid appears to have some potential as a resistance assay for Sclerotinia blight in runner peanuts, but be of limited use for screening Spanish peanuts. Rapid and accurate methods for screening peanut breeding lines for resistance to Sclerotinia blight would accelerate progress in breeding for disease-resistant peanuts.