A high epicuticular wax strawberry mutant reveals enhanced resistance to Tetranychus urticae Koch and Botrytis cinerea

Abstract

Cuticular wax is crucial for plant defense against biotic and abiotic stresses, but its relationship with resistance in strawberries is not well understood. A stable genetic mutant (MT) of ‘Benihoppe’ strawberries with a glossier leaf surface and stronger resistance was identified during cultivation. In this study, we analyzed the anatomical and physiological traits of leaves from ‘Benihoppe’ and its mutant and compared their cuticular wax properties. We also analyzed the differentially expressed genes involved in leaf cuticular wax accumulation and investigated their characteristics against Tetranychus urticae Koch and Botrytis cinerea. Comparisons between morphological and physiological features revealed that the mutant had smaller, darker leaves with a thicker upper epidermis and palisade tissue. GC-MS analysis showed that the total cuticular wax content of the MT leaf (1147.84 μg/dm2) had 1.74 times more total wax content than that of ‘Benihoppe’ (660.66 μg/dm2). The main components of cuticular wax in the MT leaf were primary alcohols (C18, C20, C22, C24, C25 and C26), alkanes (C20 and C31) and fatty acids (C26), whose content increased by 138.37%, 53.69% and 86.80%, respectively, compared with that of ‘Benihoppe’. Based on the comparative transcriptome data, we identified FaKAS2, FaFATA2, FaLACS1, FaKCS12/19, FaPAS2, FaECR, FaCER1 and FAR3/5 as potential key genes involved in wax synthesis of strawberries. Furthermore, MT leaves exhibited lower susceptibility to Tetranychus urticae Koch and its cuticular wax extraction inhibited the growth of Botrytis cinerea more effectively. Therefore, the increase of total cuticular wax and the content of major wax components in MT may be the main contributor to the enhanced resistance. These results not only deepen our understanding of the cuticular wax regulation but also provide potential gene resources for developing more resistant strawberry varieties.