Baseline sensitivity and the population shifts of Didymella rabiei in chickpea to the QoI fungicide pyraclostrobin in Alberta, Canada.

Ahmed, H.U., Chang, K.F., Hwang, S.F., Gossen, B.D., Strelkov, S.E., and Turnbull, G.D. (2014). "Baseline sensitivity and the population shifts of Didymella rabiei in chickpea to the QoI fungicide pyraclostrobin in Alberta, Canada.", Journal of Plant Diseases and Protection, 121(4), pp. 164-170.

Abstract

Ascochyta blight, caused by Didymella rabiei, is one of the most important factors limiting chickpea production worldwide. In western Canada repeated applications of the strobilurin fungicide pyraclostrobin is relied upon for the control of ascochyta blight. Pyraclostrobin sensitivity of baseline population of D. rabiei obtained from Saskatchewanduring 1997-2000 was determined. Based on colony growth the mean EC50 value of the baseline isolates was 1.0 μg ml-1. Only one isolate out of 122 isolates collected in Alberta in 2007 was sensitive at the baseline EC50of pyraclostrobin. The mean EC50value of nine Alberta isolates collected in 2007 was determined to be 90.0 μg ml-1. Based on this EC50, among the 91 isolates of 2007 60 % of the isolates were insensitive and 40 % of the isolates were sensitive, while among the 2013 isolates 81.5 % were insensitive and18.5% were sensitive. Based on the spore germination method the mean EC50value of seven isolates collected in 2007 was 1.9 μg ml-1. Data revealed a 90x increase in the mean EC50value of the 2007 isolates compared to baseline isolates, suggesting a shift in the population structure towards higher insensitivity to pyraclostrobin in western Canada.

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