The improvement of a plant's tolerance to drought is a major endeavor in agriculture.
Polyploid plants often exhibit enhanced stress tolerance relative to their diploid progenitor, but the matching stress tolerance is still little understood. Own-rooted stem cuttings of mulberry (Morus alba L.) cultivar Shinichinose (2n = 2x = 28) and Shaansang-305 (2n = 3x = 42) were used in this study, of which the latter (
triploid) has more production and application purposes. The responses of
triploid Shaansang-305 and diploid progenitor ShinIchinose under drought stress were compared through an investigation of their physiological traits,
RNA-seq, and secondary metabolome analysis. The results showed that the
triploid exhibited an augmented
abscisic acid (ABA) content and a better stress tolerance phenotype under severe drought stress. Further, in the
triploid plant some genes (TSPO, NCED3, and LOC21398866) and ATG gene related to ABA signaling showed significantly upregulated expression. Interestingly, the
triploid accumulated higher levels of RWC and SOD activity, as well as more wax on the leaf surface, but with less reductive
flavonoid than in diploid. Our results suggest
triploid plants may better adapt to with drought events. Furthermore, the
flavonoid metabolism involved in drought resistance identified here may be of great value to medicinal usage of mulberry. The findings presented here could have substantial implications for future studies of crop breeding.