Root system architecture analysis and genome-wide association study of root system architecture related traits in cotton

: Root is the main organ of plants that absorbs water and nutrients. The growth of the root system will directly affect the absorption and utilization of nutrients, the resistance to abiotic stress and finally the yield of cotton. In this study, a natural population of 220 upland cotton accessions and a chromosomal segment substitution line (CSSL) population with 325 lines, derived from the crossing and backcrossing of Gossypium barbadense acc. 3-79 with G. hirsutum cv. ‘Emian 22’ were selected to collect the major root phenotypic traits. Four major traits, namely main root length (MRL), root fresh weight (RFW), root dry weight (RDW) and lateral root angle (LRA) were investigated, and genome-wide association analysis (GWAS) was performed for four root traits in natural populations in combination with genome resequencing. The results showed that the four root traits of the natural population are all in line with normal distribution, and the CSSL population were all in skewed distribution. The mean value of root index of CSSL population was higher than that of natural population. A total of 2,714,140 SNP was obtained from the resequencing data of the natural population. The principal component analysis (PCA) showed that the RFW and MRL could be used as two indexes for cotton root classification, through which the cotton root could be divided into nine types in each population. The analysis of population structure demonstrated that the natural population can be divided into five subgroups. Ge-nome-wide association analysis rrevealed that two association sites were simultaneously associated by RFW and RDW in natural populations. The results of this study provide a theoretical basis for further research on root system architecture (RSA) and its genetic mechanism, and it is also of great significance to cotton breeding of abiotic stress resistance.