Identification and characterization of candidate genes for primary root length in Asiatic cotton (Gossypium arboreum L.).

One major gene controlling primary root length (PRL) in Gossypium arboreum is identified and this research provides a theoretical basis for root development for cotton. Primary root elongation is an essential process in plant root system structure. Here, we investigated the primary root length (PRL) of 215 diploid cotton (G. arboreum) accessions at 5, 8, 10, 15 days after sowing. A Genome-wide association study was performed for the PRL, resulting in 49 significant SNPs associated with 32 putative candidate genes. The SNP with the strongest signal (Chr07_8047530) could clearly distinguish the PRLs between accessions with two haplotypes. GamurG is the only gene that showed higher relative expression in the long PRL genotypes than the short PRL genotypes, which indicated it was the most likely candidate gene for regulating PRL. Moreover, the GamurG-silenced cotton seedlings showed a shorter PRL, while the GamurG-overexpressed Arabidopsis exhibited a significantly longer PRL. Our findings provide insight into the regulation mechanism of cotton root growth and will facilitate future breeding programs to optimize the root system structure in cotton.