Physiological response and corresponding transcriptome analysis highlight Actinidia valvata DJY-C-1 with the strongest tolerance to waterlogging stress

Waterlogging stress significantly impacts kiwifruit (Actinidia) growth and productivity. This study aims understand the physiological and molecular mechanism underlying waterlogging tolerance in kiwifruit genotypes to screen waterlogging-tolerant genotypes for rootstocks breeding. Plants with plastic bags were put into plastic bucket with water for 0 to 10 days for the water waterlogging treatments, the phenotypic changes of the three genotypes were observed. The mophological results showed that under waterlogging stress, ‘Bruno’ exhibited severe leaf damage and root inhibition, while ‘DJY-C-1′ showed the strongest tolerance and ‘DJY-B-1′ moderate tolerance.. Further analysis found that the ‘Bruno’ had a weak ability to synthesize osmotic adjustment substances and a low antioxidant capacity in its roots. Transcriptome sequencing analysis showed that differentially expressed genes (DEGs) were mainly concentrated in biological processes related to cellular stress, antioxidant defense, and protein synthesis. The genes related to glutathione metabolism were found to be up-regulated in the ‘DJY-C-1′ but stable or down-regulated in ‘Bruno’. The study successfully identified the highly tolerant genotype ‘DJY-C-1’ and revealed that kiwifruit responded to waterlogging stress by enhancing stress response and antioxidant mechanisms, as well as regulating key pathway gene expression. These findings provide a solid theoretical basis for the commercial breeding rootstocks and cultivation of Actinidia under waterlogging.