Physiological characterization of leaf‐shape isolines of upland cotton

Abstract Four major leaf shapes exist in tetraploid cotton ( Gossypium hirsutum L.): normal, sub‐okra/sea‐island, okra, and super‐okra. The majority of upland cotton ( G . hirsutum ) varieties in the United States possess a normal leaf shape. However, the other three leaf shapes were reported to show a few production advantages such as accelerated flowering rates, early maturity, reduced lint trash and boll rot, and increased pest resistance. In this study, we evaluated the leaf‐shape isolines LA‐213‐okra, LA‐213‐normal, LA‐213‐super‐okra, and LA‐213‐sub‐okra for physiological traits related to yield and performance and identified the isolines associated with superior physiological mechanisms. During flowering stage, narrow leaf shape isolines, LA‐213‐okra and LA‐213‐super okra, showed 6%–19%, 0%–15%, and 3%–73% greater chlorophyll index, quantum efficiency of photosystem II, and photosynthetic rate, respectively, than the LA‐213‐normal and LA‐213‐sub‐okra isolines. Further, the water use of LA‐213‐super‐okra was 12%–22% lower than that of the other three leaf shape isolines. With superior physiological performance, the okra and super‐okra leaf shapes offer useful trait variation for cotton breeding and variety development.