Organizing Committee


Poster Presentations


Poster Presentations


Disease reaction of maturity Group V soybean cultivars to Asian soybean rust infection and their response to foliar fungicides

Presenter: Bonnie C. Wells

Other authors and affiliations: Gabriel L. Sciumbato. Delta Research and Extension Center, Plant Pathology, Stoneville, MS 38776, U.S.A.

Asian soybean rust (ASR) disease severity evaluations were conducted for 111 maturity Group V soybean cultivars infected by Phakopsora pachyrhizi in Stoneville, MS, in 2007. Eighty-eight early Group V cultivars and 23 late Group V cultivars were planted in late July 2007 in Sharkey clay soil in a randomized complete block design with four replications. Cultivars were evaluated both untreated and treated with a tank mix of 4 oz/acre tetraconazole and 4 oz/acre pyraclostrobin. Treatments were arranged factorially and applied twice, once at R3 and once at R5. Manifestation of ASR occurred naturally in the field plots at R6 in late October. Disease severity was evaluated visually using a 0 to 5 rating scale based on the average surface area of leaf infection. Disease severity for all cultivars evaluated averaged 3.60. Significant differences in disease severity were seen between the early Group V cultivars and not, however, between the late Group V cultivars. Disease was most severe for the early cultivar AgVenture 54P1N, which averaged 4.88, while it was least severe for the early cultivar Progeny 5207, which averaged 1.63. No significant differences were seen between the fungicide-treated and untreated plots. Yield data will be obtained in November to examine each cultivar’s tolerance to ASR. Presently, no ASR resistant or tolerant cultivars are commercially available in the United States.

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