The study of epidermal wax of different apple varieties and functional analysis of MdMYB94 regulating wax...

Cuticular wax plays a crucial role in reducing water loss, enhancing pathogen resistance, and improving the surface appearance of apple fruit. However, limited research has focused on wax biosynthesis during fruit development in apple. In this study, we investigated the wax biosynthesis of four apple cultivars 'Fumei', 'Fuxing', 'Fuli', and 'Fuji'. Among them, 'Fumei' apple exhibited significantly higher wax accumulation than the other three cultivars, reaching up to 4,604,997.01 μg/dm². Scanning electron microscopy (SEM) revealed distinct wax formation patterns among the cultivars, characterized by the development of wax structures on the fruit surface. Notably, in 'Fumei', the cuticular wax layer began to thicken at 150 days after full bloom (DAFB), reaching a significantly greater thickness than that observed in the other cultivars. Gas chromatography-mass spectrometry (GC-MS) analysis revealed a substantial increase in wax content in 'Fumei' during the later stages of fruit development, with alkanes comprising 50.39 % of the total wax. Furthermore, we identified a MYB transcription factor, MdMYB94, which positively regulates wax accumulation in apple fruit. Our findings provide novel insights into the physiological and molecular characteristics of 'Fumei' as a high-wax germplasm, offering valuable theoretical and genetic resources for improving apple fruit appearance and enhancing stress resistance through breeding programs.