Physiological and transcriptome analysis provided insights for the response of yellowhorn to drought stress

This study not only provide a theoretical basis for screening drought-resistant yellowhorn rootstocks but also lay the foundation for the research on the drought resistance mechanism of yellowhorn. Drought is a major limiting factor in the production and cultivation of yellowhorn, an important woody oil species in China. It is important to select excellent drought-resistant rootstocks, and the current reproduction of rootstocks of yellowhorn is mainly through seed propagation. In this study, we analyzed the phenotypes, physiology and anatomy of the F1 generation of five yellowhorn varieties (‘Zhongshi 1’, ‘Zhongshi 4’, ‘Zhongshi 7’, ‘Zhongshi 9’ and ‘Yuanda’) which are currently the main promoted varieties of yellowhorn. The changes in physiological traits were used to comprehensively rank drought resistance by the membership function method. The results showed that the drought resistance of different varieties was in the order ‘Zhongshi 9’ > ‘Zhongshi 4’ > ‘Yuanda’ > ‘Zhongshi 7’ > ‘Zhongshi 1’. In addition, we investigated the molecular signature of two yellowhorn varieties exhibiting a large difference in levels of drought resistance using transcriptome data. A total of 119 differentially expressed genes (DEGs) were found between the 2 yellowhorn varieties under drought stress. Based on KEGG analysis, DEGs were mostly enriched in three pathways. According to the correlation analysis between weighted gene co-expression network analysis (WGCNA) and physiological traits, a total of four co-expression networks with high correlation were constructed, and some hub genes of yellowhorn in response to drought stress were found. We carried out a comprehensive evaluation of yellowhorn drought tolerance based on parental lines. It solves the current problems faced in the breeding of yellowhorn and lays the foundation for studying the molecular mechanism of drought resistance in yellowhorn.