Effects of drought on agronomic and fiber quality in an introgressed backcross inbred line population of Upland cotton under field conditions

Upland cotton (Gossypium hirsutum) is the most important fiber crop and an important oilseed crop in the world. Developing drought tolerant cultivars is important to sustainable cotton production in arid and semi-arid regions. However, there is a lack of information on genetic variation for drought tolerance in breeding populations. In this study, a backcross inbred line (BIL) Upland population with germplasm introgression from a more drought-tolerant American Pima cotton (G. barbadense) parent was evaluated in multiple field environments under well-watered (WW) and water-limited (WL) conditions at the flowering stage. Drought at the flowering stage reduced seedcotton yield (SCY), lint yield (LY), boll weight (BW), fiber length (FL), and fiber strength (STR) but increased lint percentage (LP), micronaire (MIC), neps per size, nep per gram, seedcoat nep size, and seed coat fragment count by gram. Significant genetic differences in the BIL population were detected for most agronomic and fiber quality traits and drought susceptibility index (DSI) for these traits. DSI of SCY and LY ranged from 0.01 to 1.5 and 0.1-1.45, respectively, reflecting the tolerance level of the BILs under WL conditions. The broad-sense heritability estimates were moderate for most agronomic traits and moderate to high for most fiber quality traits. Results indicated that highly positive correlation was detected for agronomic and fiber quality traits between WW and WL conditions, with the highest correlations for SCY, LY, UHM, SCY, and MIC. Promising BILs with drought tolerance were identified. This study has provided a line of evidence that field drought tolerance was transferred from the more drought tolerant Pima line to Upland cotton.