Roses (Rosa hybrida) are the most popular cut flower plants worldwide, accounting for over a third of the global cut flower industry. Gray mold, caused by Botrytis cinerea, is often referred to as the postharvest "cancer" of cut roses and represents the most significant disease impacting the postharvest preservation of these flowers in China. Currently, research progress in this area has been limited. Our study utilized single-cell RNA sequencing technology to elucidate the mechanisms underlying B. cinerea resistance in R. hybrida “Jumilia.” We identified seven distinct cell groups within rose petals. The rose epidermis acts as the physical barrier of defense against B. cinerea, while the infection rate may be accelerated through vascular tissues. Furthermore, we identified several key genes, including pectin methylesterases, pathogenesis-related proteins, glutathione S-transferase, and endochitinase EP3, which may play crucial roles in the stress response. The biosynthesis of secondary metabolites temporarily mitigates the infection process, and pathogenesis-related proteins have been recognized as key regulatory genes. This preliminary study elucidates the cellular changes and molecular mechanisms involved in B. cinerea infection in rose petals at the single-cell level. Our findings provide new insights into the defense mechanisms of roses against fungal diseases.

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