|ALZOHAIRY, S.A. - Michigan State University|
|GILLET, J - Michigan State University|
|MILES, T - Michigan State University|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/6/2020
Publication Date: 7/4/2021
Citation: Alzohairy, S., Gillet, J., Saito, S., Naegele, R.P., Xiao, C., Miles, T. 2021. Fungicide resistance profiles of Botrytis cinerea isolates from Michigan vineyards and development of a TaqMan assay for detection of fenhexamid resistance. Plant Disease. 105(2):285-294. https://doi.org/10.1094/PDIS-05-20-1087-RE.
Interpretive Summary: Botrytis cinerea, commonly called gray mold, causes rot and disease on many crops including grapes. To control this pathogen, growers frequently apply fungicides. Over time the pathogen can develop resistance to specific fungicides. Developing tools, like molecular markers to detect resistance to fungicides can help growers to develop more effective spray programs and reduce fungicide applications.
Technical Abstract: Botrytis cinerea on grapes causes bunch rot at both pre- and post-harvest stages, where losses can reach up to 100%. Chemical control primarily relies on the prophylactic use of site-specific fungicides. Repeated applications of these products raise the risk of fungicide resistance development in B. cinerea populations, resulting in crop management failures. To determine the extent of resistance, B. cinerea isolates were collected from grape clusters in the northwest and southwest grape growing regions of Michigan in 2014 (n = 115) and 2018 (n = 125). These isolates were phenotyped using discriminatory doses of 8 fungicides to determine the levels of resistance. Fungicide resistance increased from 2014 to 2018 with a higher increase in fenhexamid, fluopyram, and iprodione resistance. B. cinerea isolates resistant to multiple fungicides were detected in 2014 and 2018 with a higher frequency of resistance to higher number of fungicides of different classes being observed in 2018. TaqMan real time PCR has been developed to detect B. cinerea fungicide resistance to fenhexamid and to differentiate the erg27 F412S/I/V alleles. The assay was tested for sensitivity, specificity, and reproducibility on purified DNA and infected grape tissue samples. The data provide essential information to growers about the efficacy for B. cinerea control using the available botryticides. Further, the developed fenhexamid markers will be transferred to diagnostic clinics to assist growers in the management of bunch rots before resistance related control failures occur.