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Title: Characterization of white mold disease avoidance in common bean

Author
item Miklas, Phillip - Phil
item Porter, Lyndon
item KELLY, JAMES - Michigan State University
item MYERS, JAMES - Oregon State University

Submitted to: European Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2012
Publication Date: 1/7/2013
Citation: Miklas, P.N., Porter, L., Kelly, J., Myers, J. 2013. Characterization of white mold disease avoidance in common bean. European Journal of Plant Pathology. 135:525-543.

Interpretive Summary: White mold is the most important disease of common bean in the US and the most difficult to control. Integrated strategies using cultural practices, fungicides, irrigation scheduling and resistance in the bean host are required for optimal control. This report focuses on disease avoidance characteris in the bean host conferred by archicultural traits. We identifed 13 genomic regions conferring disease avoiadance traits. Six of these regions have a stong association with white mold resistance in the field. A review of white mold field trials conducted aver 12 years and three states, MI, OR, and WA, revealed that lodging resistance was the most important trait for avoiding whtie modl disease. New germplasm releases with combined disease avoidance and physiological resistance did not require fungicide protection to realize full yield potential. This study emphasizes the need to conduct long term field screening trials to incorporate avoidance and pyhsiological resistance to combat this devastating disease.

Technical Abstract: White mold, caused by Sclerotinia sclerotiorum, is a devastating fungal disease of common bean (Phaseolus vulgaris L.) worldwide. Physiological resistance and disease avoidance conferred by plant architecture-related traits contribute to white mold field resistance. Our objective was to further examine white mold disease avoidance in common bean. A comparative map composed of 79 quantitative trait loci (QTL) for white mold resistance (27), disease avoidance traits (36) and root traits (16) was generated. Thirteen white mold resistance QTL, six with strong and seven with weak associations with disease avoidance traits, were observed. Root length and lodging QTL co-located in three regions. Canopy porosity and height, and lodging were highly correlated with disease severity score in field screening trials conducted from 2000 to 2011. Resistance to lodging was extremely important for reducing disease severity in both dry and snap bean (r = 0.61 across 11 trials). Avoidance traits were less effective in reducing disease severity in trials with heavy disease pressure. Dry bean lines with physiological resistance in combination with disease avoidance traits did not require fungicide application to protect yield potential under moderate and heavy disease pressure. Given complexity of disease resistance as evidenced by the comparative map, marker-assisted breeding for disease avoidance is not recommended at this time. Instead, selecting for resistance to white mold in the field, in combination with high yield potential and acceptable maturity, is the recommended strategy for improving both disease avoidance and physiological resistance to white mold in cultivars with commercially acceptable agronomic traits.