Sensitivity of Colletotrichum fructicola and Colletotrichum siamense of Peach in China to Multiple Classes of Fungicides and Characterization of Pyraclostrobin-Resistant Isolates

Abstract

Anthracnose, mainly caused by Colletotrichum gloeosporioides species complex including C. fructicola and C. siamense, is a devastating disease of peach. The chemical control has been widely used for years and management failures have increased towards commonly used fungicides. Therefore, screening of sensitivity of Colletotrichum spp. to fungicides with different modes of action is needed to make proper management strategies for peach anthracnose. In this study, sensitivity of 80 isolates of C. fructicola and C. siamense was screened for pyraclostrobin, procymidone, prochloraz and fludioxonil based on mycelial growth inhibition at discriminatory doses. Results showed that C. fructicola and C. siamense isolates were highly resistant to procymidone and fludioxonil with 100% resistance frequencies to both fungicides, but sensitive to prochloraz, i.e., no resistant isolates were found. For pyraclostrobin, 74% of C. fructicola isolates showed high resistance and 26 % were low resistant, all of the C. siamense isolates were low resistant. No positive cross-resistance was observed between pyraclostrobin and azoxystrobin, even they are members of the same quinone outside inhibitor (QoI) fungicide group, and between pyraclostrobin and non-QoIs. Resistant isolates to QoI fungicides were evaluated for the fitness penalty. Results showed that no significant differences except for mycelial growth rates were detected between highly resistant and low-resistant isolates of C. fructicola. Molecular characterization of Cyt b gene revealed that the G143A point mutation was the determinant of the high resistance in C. fructicola. This study demonstrated the current resistance status of C. fructicola and C. siamense to different fungicides and their future perspectives. Demethylation inhibitor (DMI) fungicides are the best option among different chemicals to control peach anthracnose in China.

Colletotrichum Species Associated with Peaches in China

“…Meanwhile, all C. nymphaeae strains in this study have been confirmed to be resistant to carbendazim (MBC) [ 75 ]. C. nymphaeae was reported to be less sensitive to demethylation inhibitor (DMIs) fungicides (flutriafol and fenbuconazole) compared with C. fioriniae , C. fructicola , and C. siamense [ 21 ] and C. gloeosporioides was reported to be inherently tolerant to fludioxonil [ 76 , 77 ]. Most of the peach farms in China are small and there is vast diversity in the approaches to managing diseases.…”

Sterol demethylation inhibitor fungicide resistance in Colletotrichum siamense from chili is caused by mutations in CYP51A and CYP51B

“…The five genotype mutations in CYP51A and CYP51B of C. siamense have not yet been reported in other Colletotrichum species. Recent studies showed that C. siamense isolates from peach in China were sensitive to prochloraz, while those from apple in Illinois of the United States were sensitive to propiconazole (Chechi et al 2019;Usman et al 2021). C. siamense isolates from strawberry in China were sensitive to difenoconazole, tebuconazole and prochloraz (Zhang et al 2020).…”

Sensitivity of <i>Colletotrichum gloeosporioides</i> species complex (CGSC) isolated from strawberry in Taiwan to benzimidazole and strobilurin

“…had higher sensitivity to pyraclostrobin than other strobilurin fungicides. 46,47) Several reasons are suspected to be associated with the higher ability of pyraclostrobin to inhibit the mycelial growth of CGSC. First, pyraclostrobin, recommended in 2002 for controlling strawberry anthracnose, was released later than azoxystrobin, kresoxim-methyl, and trifloxystrobin.…”