Title : Genomic architecture of biomass heterosis in Chinese cabbage
Abstract:
Heterosis is a complex biological phenomenon in which hybrids exhibit superior phenotypic characteristics, such as enhanced biomass production, developmental rates, grain yields and stress tolerance. Chinese cabbage (Brassica rapa) is a major edible leafy-producing crop, and its F1 hybrids have been widely used in commercial production for many years. In this study, we generated 135 intraspecific hybrids by crossing 28 Chinese cabbage accessions. The agronomically important traits were evaluated comprehensively, including yield of whole plant gross weight, net weight, leaf weight, leaf number, plant height, head height, head width, head leaf number, plant diameter and head core length, at 70 d after sowing (DAS). We observed strong positive correlations among biomass, leaf weight and net weight in hybrids, indicating that both net weight and leaf weight were the main contributors to hybrid biomass. To identify loci or genes with the potential contribution to Chinese cabbage biomass heterosis, we conducted large-scale genome-wide association study (GWAS) analyses on heterosis for the complex agronomic traits using an algorithm for compressed mixed linear model in GAPIT software. A total of 764 protein-coding genes within the 10-kb genomic regions surrounding the heterosis-associated SNPs were identified and thought to be candidate genes for biomass heterosis in Chinese cabbage. Of the 764 genes, 547 genes had functional annotations for biological process categories in the GO database. These genes were divided into diverse functional categories, including the generic categories such as cellular processes, intracellular part, metabolic processes and developmental processes, and the specific categories such as photosynthetic membrane, nitrogen compound metabolic process, unidimensional cell growth, cell division, reproductive process, cell proliferation, indicating the collective contribution of these biological pathways to biomass heterosis in Chinese cabbage.
