Baseline Sensitivity and Resistance of Botrytis cinerea to Penthiopyrad in Hebei Province, China

Tomato gray mold (TGM), caused by Botrytis cinerea, is a destructive disease of greenhouse tomatoes. Its control mainly depends on the application of chemical fungicides. In China, penthiopyrad has been registered for the management of TGM for about 3 years. In this study, the baseline sensitivity of B. cinerea to penthiopyrad was measured based on mycelial growth and spore germination, using 131 wild isolates collected from Hebei Province. The mean EC50 values 1.054 +/- 0.633 mg/L (on mycelial growth) and 0.101 +/- 0.037 mg/L (on conidia germination) were used as the baseline sensitivity. Isolates (187) of B. cinerea, sampled from eight regions in Hebei province during 2021 and 2022, were used for resistance studies by mycelial growth method. Based on the resistance factor, these isolates were considered: sensitive (=65 isolates), low (=39 isolates), moderate (=38 isolates), and high (=45 isolates) resistance. All 15 isolates from Raoyang were sensitive to penthiopyrad. Four mutation types in the sdhB subunit, namely H272R, N230I, P225F, and P225L, were associated with the resistance to penthiopyrad. A positive cross-resistance was also recorded between penthiopyrad and fluopyram, boscalid, or pydiflumetofen. These results provide useful information on the chemical control of TGM.

Automated summary

This study evaluated the baseline sensitivity of Botrytis cinerea to penthiopyrad, a registered fungicide for the management of tomato gray mold (TGM) in China. The resistance of B. cinerea isolates from different regions in Hebei province was also investigated, and four mutation types associated with penthiopyrad resistance were identified. The study revealed the presence of cross-resistance between penthiopyrad and other fungicides, providing important information for the chemical control of TGM.