Root Growth Parameters of Converted Race Stocks of Upland Cotton and Two BC2F2 Populations

Abstract

Genetic modification of the rooting system may lead to more drought tolerant upland cotton, Gossypium hirsutum L. This experiment was designed to evaluate rooting traits at the seedling stage for 68 Converted Race Stocks (CRS) compared with TAM94L‐25 and ‘Lankart 142’, and to investigate the recoverability of robust rooting traits in two BC2F2 populations derived by crossing a robust (M‐9044‐0031) and a nonrobust (M‐9044‐0057) rooting CRS donor parent with TAM94L‐25. Initial screen of the CRS showed that genetic variation occurred among the 68 accessions for root length (RL), lateral root number (LRN), root fresh weight (RFW), lateral root dry weight (LRDW), and total root dry weight (TRDW). There was a 2.3‐, 2.6‐, 4.6‐, 4.8‐, and 4.4‐fold difference among the 11 most robust and 11 least robust rooting CRS accessions for RL, LRN, RFW, LRDW, and TRDW, respectively. However, no CRS were identified that were superior to the elite germplasm and BC2F2 recurrent parent, TAM94L‐25. The robust rooting population of M‐9044‐0031/3*TAM94L‐25 produced longer RL and more LRN per plant than the nonrobust rooting population of M‐9044‐0057/3*TAM94L‐25. However, no differences were observed between the two BC2F2 populations for root weight parameters. Results suggest that the day‐neutral CRS accessions have useful genetic variability for root growth parameters, that robustness of seedling rooting parameters can be recovered easily, and that seedling rooting robustness can be improved by crossing robust rooting parents.