Influences of the combination of high temperature and water deficit on the heritabilities and correlations of agronomic and fiber quality traits in upland cotton

With climate change manifested in cotton growing regions primarily as a combination of rising temperatures and prolonged periods of low rainfall, it has become critical to improve the resiliency of upland cotton (Gossypium hirsutum L.) to concurrent heat and drought stress. However, few investigations have considered the effect of this combined stress exposure on the phenotypic and genotypic correlations between important cotton traits, or on their respective heritabilities. To that end, we evaluated two upland cotton recombinant inbred line (RIL) populations under managed well-watered (WW) and water-limited (WL) irrigation regimes in the presence of high temperature across multiple environments. In both RIL populations, the broad-sense heritability for lint yield was higher under WW relative to WL conditions. The highest broad-sense heritabilities in both irrigation regimes were observed for lint percentage and fiber quality (micronaire, length, strength, uniformity, and elongation) traits. The genotypic correlations between lint yield and percentage were among the strongest values estimated, followed by a range of non-significant to moderately strong genotypic correlations between lint percentage and the five fiber quality traits in the two RIL populations. Within a RIL population, the strength and direction of between-trait phenotypic and genotypic correlations were similar for WW relative to WL conditions, although there were notable differences for them between RIL populations. Taken together, these results have the potential to benefit climate-oriented breeding programs when developing selection and testing schemes for the genetic improvement of cotton traits with a variable range of environmental stability under heat and drought stress.