Physiological studies and transcriptomic analysis reveal the mechanism of saline–alkali stress resistance of Malus sieversii f. niedzwetzkyan

Abstract

Abstract Apple (Malus) is one of the world’s most economically significant fruit varieties. The inability of apple trees to tolerate saline–alkali soil has long limited their growth and yield. Malus sieversii f. niedzwetzkyan is a wild species capable of growing on saline–alkali soil in Xinjiang.Here, we conducted a hydroponic experiment in which M. niedzwetzkyana and M. domestica “Royal Gala” seedlings were subjected to 150 mM saline–alkali stress. Physiological data indicated that the saline–alkali resistance of M. niedzwetzkyana was higher than that of M. “Royal Gala,” as the concentrations of ROS were lower and Na+/K+ ratios were higher in M. niedzwetzkyana than in M. “Royal Gala” under saline–alkali stress. Transcriptome analysis was conducted on the leaves and roots of M. niedzwetzkyana at different time points under saline–alkali stress (0 h, 6 h, and 12 h). A total of 599 differentially co-expressed genes associated with saline–alkali stress were identified. GO and KEGG pathway analysis revealed that DEGs in the leaves were enriched in glutathione metabolism, hydrolase activity, and heme binding following exposure to saline–alkali stress. However, DEGs in the roots were enriched in phenylpropanoid biosynthesis, flavonoid biosynthesis and iron ion binding. We identified hub genes related to superoxide dismutase and Na+, K+ transport using weighted gene co-expression network analysis.Our findings provided new insights into the saline–alkali tolerance of M. niedzwetzkyana at the physiological and molecular levels. this research provides an important genetic resource for identifying genes involved in responses to saline–alkali stress.