Molecular mechanism of reduced biological fitness of fludioxonil‐resistant strains of Botrytis cinerea based on transcriptome analysis

Abstract BACKGROUND Fludioxonil is a fungicide used to control gray mold. However, the frequency of resistance in the field is low, and highly resistant strains are rarely isolated. The biological fitness of the resistant strain is lower than that of the wild strain. Therefore, the molecular mechanism underlying the decrease in the fitness of the fludioxonil‐resistant strain of Botrytis cinerea was explored to provide a theoretical basis for resistance monitoring and management. RESULTS Transcriptome analysis was performed on five different‐point mutant resistant strains of fludioxonil, focusing on mining and screening candidate genes that lead to reduced fitness of the resistant strains and the functional verification of these genes. The differentially expressed genes (DEGs) of the five point‐mutation resistant strains intersected with 1869 DEGs. Enrichment analysis showed that three downregulated genes ( Bcin05g07030 , Bcgad1 , and Bcin03g05840 ) were enriched in multiple metabolic pathways and were downregulated in both domesticated strains. Bcin05g07030 and Bcin03g05840 were involved in mycelial growth and development, pathogenicity, and conidial yield, and negatively regulated oxidative stress and cell wall synthesis. Bcgad1 was involved in mycelial growth and development, conidial yield, oxidative stress, and cell wall synthesis. Furthermore, Bcin05g07030 was involved in osmotic stress and spore germination, whereas Bcin03g05840 and Bcgad1 negatively regulated osmotic stress and cell wall integrity. CONCLUSION These results enable us to further understand the molecular mechanism underlying the decrease in the biological fitness of B. cinerea fludioxonil‐resistant strains. © 2024 Society of Chemical Industry.