Elucidating Genetic Mechanisms of Summer Stress Tolerance in Chinese Cabbage through GWAS and Phenotypic Analysis

The development of Chinese cabbage (Brassica rapa subsp. pekinensis) varieties that are resilient to climate change is becoming increasingly critical. Our study focused on developing stress-tolerant Chinese cabbage during the summer season to minimize the impacts of global climate change. We evaluated 52 Chinese cabbage accessions grown in the field during the late spring–summer season in Korea. Various phenotypic data of Chinese cabbage in adverse environments were collected from field data. In addition to field screening, we used a controlled-environment chamber to observe the direct impact of heat on young plants, particularly in the root area. A genome-wide association study was conducted using two sets of phenotypic data collected from both chamber and field studies and genotype data acquired from GBS analyses. A total of 57 SNPs distributed across all 10 B. rapa chromosomes were selected to be highly related to the target traits. Several candidate genes were annotated using the flanking sequences of these SNPs. The study revealed that most of the annotated genes seemed to be highly connected with the function of the heat stress response. Other genes were also found to be related to the environmental stress response and flowering. These candidate SNPs and genes can provide valuable tools for breeders to develop summer stress-tolerant Chinese cabbage varieties.