Fungicide-enhanced differentiation and multidrug resistance of Botrytis cinerea on greenhouse tomato

Botrytis cinerea, a necrotrophic fungal pathogen, causes rotting of tomato at both pre-harvest and postharvest stages. Fungicide practices often lead to differential resistance in isolates, necessitating detailed differentiation profiles for effective control. This study tested the resistance of B. cinerea isolates to eight fungicides (boscalid (Bos), pyrimethanil (Pyr), cyprodinil (Cyp), iprodione (Ipr), procymidone, tebuconazole, prochloraz, and pyrisoxazole), evaluated fitness penalties in radial growth, conidial production, and pathogenicity, and primarily explored the differentiation mechanism via infection cushion (IC) formation, autophagy, and mitochondrial metabolism. Results revealed that isolates QN01 and TL03 showed resistance to Bos, Pyr, and Cyp, with EC₅₀ values of 38.53, 50.04, 11.95 μg/mL (QN01) and 23.58, 26.27, 8.16 μg/mL (TL03), respectively, and remained sensitive to other fungicides, exhibiting a Pyr^HRBos^MRCyp^R resistance phenotype, while other isolates were sensitive to all tested fungicides. All isolates were capable of thriving growth, but significant differed in conidia production, pathogenicity, and sensitivity to fungicides in conidial germination and tube elongation. Moreover, QN01 was highly surface-sensitive for IC production, with accumulated autophagy, while TL03 showed marked conidiation differentiation and higher citrate, oxalate, and phosphate levels. Upon iprodione treatment, QN01's citrate and phosphate levels increased while TL03's decreased, accompanying with QN01 depleting oxalate faster than TL03. The results highlighted the fungicide-enhanced differentiation and the mycelial growth-linked resistance among isolates, emphasizing dicarboximides, triazoles, and pyrisoxazole as effective agents for grey mold management.