Resistance to Boscalid inBotrytis cinereaFrom Greenhouse-Grown Tomato

Abstract

Grey mold, caused by the fungus Botrytis cinerea Pers ex Fr., is one of the most destructive spoilage diseases, severely affecting tomato production in Henan Province, China. Spraying fungicides from the flowering to the harvest stage is a necessary measure to reduce losses associated with B. cinerea infection. However, B. cinerea has developed resistance to fungicides in many countries. Boscalid is a succinate dehydrogenase inhibitor (SDHI) fungicide, and was registered for the control of grey mold. In this study, a total of 269 B. cinerea isolates were collected from tomato in commercial greenhouses in different locations of Henan Province, in 2014 and 2015. The sensitivity and resistance of B. cinerea field isolates were determined based on mycelial growth. The effective concentration 50 (EC50) ranged from 0.11 to 15.92 μg ml−1 and 0.16 to 8.54 μg ml−1, in 2014 and 2015, respectively. The frequency of low resistance to boscalid was 12.6% and 7.6%, and moderate resistance were 2.7% and 1.3%, in 2014 and 2015, respectively. No high-resistant isolates were found in Henan Province, China. Mycelial growth, mycelial dry weight, spore production, and pathogenicity were not significantly different between resistant and sensitive phenotypes of the B. cinerea isolates. The results of cross-resistance test showed no correlation between boscalid and carbendazim, procymidone, pyrimethanil, fluazinam or fluopyram. In this study, the succinate dehydrogenase gene B (sdhB), C (sdhC), and D (sdhD) were analyzed and compared in sensitive, low and moderately resistant B. cinerea isolates to boscalid. Results showed point mutations occurred simultaneously at sdhC amino acid positions 85 (G85A), 93 (I93V), 158 (M158V), and 168 (V168I) in 4 out of 10 sensitive isolates, 23 out of 26 low and 5 out of 5 moderately resistant B. cinerea isolates to boscalid. No point mutations were found in the sdhB and sdhD genes of all isolates. Furthermore, no point mutations were found in sdhB, sdhC and sdhD genes in 3 out of 26 low resistant B. cinerea isolates to boscalid. Therefore, we speculate the simultaneous point mutations in the sdhC gene may not be related to the resistance of B. cinerea to boscalid. These results suggested that there might be a substitution mechanism for the resistance of B. cinerea to the SDHI fungicide boscalid.

Baseline sensitivity and resistance analysis of fluopyram against Botrytis cinerea from tomato in Liaoning Province, China

“…There were irregular point mutations in C subunit of all strains. Zhang's research also found the irregular mutations in the C subunit (Zhang, Han, et al, 2015), and Liu's reports speculate the simultaneous point mutations in the sdhC gene may not be related to the resistance of B. cinerea to boscalid (Liu et al, 2021), which is consistent with our research. At present, the mutation site of SDH is mainly on the SDHB subunit, in addition to the report that the N230I mutation causes the resistance of B. cinerea to fluopyram, the histidine mutation at position H272L/R/Y and the proline mutation at position P225F are relatively common (Gao et al, 2021; Laleve et al, 2014).…”

“…In Weber's report, H272Y mutations with high resistance to boscalid showed sensitivity or resistance to fluopyram (Weber et al, 2015); meanwhile, some isolates that are resistant to fluopyram have no mutations in SDHB subunit. Liu's reports showed that no point mutations were found in the SDHB genes of many low‐resistant and moderately resistant strains of B. cinerea (Liu et al, 2021). Moreover, in the SDHB of some of these isolates, mutations were detected, and some of them were not detected (Amiri et al, 2020).…”

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

“…cinerea has developed resistance to different kinds of fungicides. B. cinerea resistance to SDHI fungicides has been reported in multiple areas [15,16,26,27]. In the current study, the resistance isolates of B. cinerea to penthiopyrad were sampled from tomatoes from commercial greenhouses in Hebei Province and tested by the mycelial growth assay.…”

“…The Fusarium graminearum with the point mutants SdhB H248Y/R exhibit decreased sensitivity to pydiflumetofen [14]. In the sensitive and low-resistance isolates of B. cinerea to boscalid, four simultaneous dependent mutations in the sdhC subunit (G85A, I93V, M158V, and V168I) were detected [15].…”

“…SDHI fungicides such as fluopyram and boscalid have been widely used to manage TGM for years. B. cinerea has developed resistance to SDHI fungicides in the field [15,16]. However, there has not been any reports on B. cinerea resistant to penthiopyrad in Hebei Province, China.…”