Seedling root QTLs analysis on dynamic development and upon nitrogen deficiency stress in Upland cotton

Abstract

Roots are vital to plant anchorage and efficient uptake of water and nutrients, and play an important role in environmental fitness, performance and yield formation in crops. The main objective of this study was to dissect the developmental behavior of seedling root traits at different developmental stages, and try to explore stress effect of nitrogen deficiency at seedling stage by mapping quantitative trait loci (QTLs) using an intraspecific population of recombinant inbred lines in Upland cotton (Gossypium hirsutum L.). Totally, 34 QTLs and 27 conditional QTLs for root length, root surface area, root volume, number of root tips and number of root forks were detected, respectively, in which 18 were congruent QTLs. The performance of five seedling root traits and QTLs showed obvious dynamic characteristics at three developmental stages. Special conditional QTLs were detected by QTL mapping strategy, in which conditional QTLs with different effects were identified at certain stages, demonstrating that the expression of genes showed temporal characteristics during root development. After nitrogen deprivation and deficiency stress for five days, a total of 11 QTLs were identified. Of these, ten QTLs were also identified in previous three stages under normal nutritional condition, and one QTL qNRT-chr19-1 referring number of root tips was newly detected, which suggested that it might be related to stress response of N-deficiency. After nitrogen deprivation for eight days, a total of 5 QTLs for plant height, maximum root length, fresh weight of root, and root/shoot ratio were identified. These QTLs and dynamic QTLs might offer different clues to understand the developmental mechanism and genetic basis of seedling root traits and to select root trait architecture in breeding program of Upland cotton.