Multi-resistance of Botrytis cinerea isolates from ginseng growing regions in China to carbendazim, iprodione and pyrimethanil

Botrytis cinerea, the fungal pathogen that causes grey mold in many crops, including the herbal medicinal plant ginseng (Panax ginseng), frequently exhibits multi-resistance. In this study, the sensitivity of 102 ginseng B. cinerea isolates collected from 11 ginseng growing regions in Jilin, Liaoning and Heilongjiang Provinces of China in 2018 and 2019 was examined. A total of 100%, 72.55% and 76.47% of the isolates were resistant to carbendazim (C), pyrimethanil (P) and iprodione (I), respectively. Four fungicide resistance patterns, including CᴿPᴿIᴿ, CᴿPSIᴿ, CᴿPᴿIS and CᴿPSIS, were identified, comprising 58.82%, 17.65%, 13.73% and 9.80%, respectively. The frequency and level of resistance of the isolates resistant to pyrimethanil and iprodione clearly varied among ginseng growing regions and lack significant cross-resistance. The geographic origins lacked any apparent correlation to pathogenicity, while the pathogenicity of isolates with the SC and M phenotypes was clearly higher than those with the SP phenotype. All the isolates resistant to carbendazim harbored a point mutation of E198A (Glu→Ala), E198V (Glu→Val), or E198K (Glu→Lys) at codon 198 in the β-tubulin gene, while isolates resistant to iprodione harbored a point mutation of I365S (Ile→Ser) or I365N (Ile→Asn) at codon 365, or point mutations of Q369P (Gln→Pro) + N373S (Asn→Ser) at codons 369 and 373 in the BcOS-1 gene. The patterns of point mutations in these genes closely correlated with the geographic origins, and the resistance of isolates that had the Q369P + N373S mutations was higher than those that had the I365S and I365N mutations. All these results provide a relatively clear understanding of the multi-resistance and molecular mechanism of B. cinerea isolates from ginseng growing regions in China. The variation in pathogenicity and the fungicide resistance of these isolates was revealed, which will help to establish a more effective strategy to control ginseng grey mold.