TY - JOUR
T1 - Resistance to QoI fungicides in ascochyta rabiei from chickpea in the Northern Great Plains
AU - Wise, K. A.
AU - Bradley, C. A.
AU - Pasche, J. S.
AU - Gudmestad, N. C.
PY - 2009/5
Y1 - 2009/5
N2 - Wise, K. A., Bradley, C. A., Pasche, J. S., and Gudmestad, N. C. 2009. Resistance to QoI fungicides in Ascochyta rabiei from chickpea in the Northern Great Plains. Plant Dis. 93:528-536. Ascochyta blight, caused by Ascochyta rabiei (teleomorph: Didymella rabiei), is an important fungal disease of chickpea (Cicer arietinum). A monitoring program was established in 2005 to determine the sensitivity of A. rabiei isolates to the QoI (strobilurin) fungicides azoxystrobin and pyraclostrobin. A total of 403 isolates of A. rabiei from the Northern Great Plains and the Pacific Northwest were tested. Ninety-eight isolates collected between 2005 and 2007 were tested using an in vitro spore germination assay to determine the effective fungicide concentration at which 50% of conidial germination was inhibited (EC 50) for each isolate-fungicide combination. A discriminatory dose of 1 μg/ml azoxystrobin was established and used to test 305 isolates from 2006 and 2007 for in vitro QoI fungicide sensitivity. Sixty-five percent of isolates collected from North Dakota in 2005, 2006, and 2007 and from Montana in 2007 were found to exhibit a mean 100-fold decrease in sensitivity to both azoxystrobin and pyraclostrobin when compared to sensitive isolates, and were considered to be resistant to azoxystrobin and pyraclostrobin. Under greenhouse conditions, QoI-resistant isolates of A. rabiei caused significantly higher amounts of disease than sensitive isolates on azoxystrobin- or pyraclostrobin-amended plants. These results suggest that disease control may be inadequate at locations where resistant isolates are present.
AB - Wise, K. A., Bradley, C. A., Pasche, J. S., and Gudmestad, N. C. 2009. Resistance to QoI fungicides in Ascochyta rabiei from chickpea in the Northern Great Plains. Plant Dis. 93:528-536. Ascochyta blight, caused by Ascochyta rabiei (teleomorph: Didymella rabiei), is an important fungal disease of chickpea (Cicer arietinum). A monitoring program was established in 2005 to determine the sensitivity of A. rabiei isolates to the QoI (strobilurin) fungicides azoxystrobin and pyraclostrobin. A total of 403 isolates of A. rabiei from the Northern Great Plains and the Pacific Northwest were tested. Ninety-eight isolates collected between 2005 and 2007 were tested using an in vitro spore germination assay to determine the effective fungicide concentration at which 50% of conidial germination was inhibited (EC 50) for each isolate-fungicide combination. A discriminatory dose of 1 μg/ml azoxystrobin was established and used to test 305 isolates from 2006 and 2007 for in vitro QoI fungicide sensitivity. Sixty-five percent of isolates collected from North Dakota in 2005, 2006, and 2007 and from Montana in 2007 were found to exhibit a mean 100-fold decrease in sensitivity to both azoxystrobin and pyraclostrobin when compared to sensitive isolates, and were considered to be resistant to azoxystrobin and pyraclostrobin. Under greenhouse conditions, QoI-resistant isolates of A. rabiei caused significantly higher amounts of disease than sensitive isolates on azoxystrobin- or pyraclostrobin-amended plants. These results suggest that disease control may be inadequate at locations where resistant isolates are present.
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U2 - 10.1094/PDIS-93-5-0528
DO - 10.1094/PDIS-93-5-0528
M3 - Article
AN - SCOPUS:67049158453
SN - 0191-2917
VL - 93
SP - 528
EP - 536
JO - Plant Disease
JF - Plant Disease
IS - 5
ER -