Resistancetoboscalidin<italic>Botrytiscinerea</italic>inZhejiangProvince

Shift of sensitivity to boscalid in Botrytis cinerea collected from plastic tunnels growing fruits and vegetables in Zhejiang Province was monitored by the mycelial growth rate assay based on our previously reported sensitivity baseline, (1.07 ± 0.11) mg/L for the wild sensitive isolates collected from 2004 to 2006. The results showed that resistance to boscalid in B. cinerea was developed rapidly. The mean EC₅₀ was (5.23 ± 7.79) and (24.30 ± 49.33) mg/L, respectively for isolates collected during 2012 to 2013 and during 2017 to 2018. The total resistance frequency during 2012 to 2013 was 15.3% and all resistant isolates were low-level resistant (LR). For the isolates collected from 2017 to 2018, the total resistance frequency was increased to 53.2%, including 7.5% MR isolates and 1.3% HR isolates. There was no significant difference in mycelial growth, sporulation, sclerotial production, and pathogenicity between boscalid resistant and sensitive isolates. No point mutation was detected in SDH A and SDH D. However, a single point mutation, H272R, P225, or N230I, was found in SDH B of all boscalid-resistant B. cinerea. Among them, 88.5% of resistant isolates were H272R. And no obvious association was found between boscalid-resistance and mutations (G85A + I93V + M158V + V168I) in SDH C.