Genotypic variation in functional contributors to yield for a diverse collection of field-grown cotton

Yield improvement in cotton could be accelerated through selection for functional yield drivers such as interception of cumulative photosynthetically active radiation ( n-ary sumation IPAR), radiation use efficiency (RUE), and harvest index (HI). However, information on the extent to which these traits vary in cotton in the southeastern United States is limited. It was hypothesized that functional yield drivers would vary significantly within a diverse cotton collection. This study was conducted in Tifton and Athens, GA, and included a total of 4 site-years. Lint yield, total biomass production, n-ary sumation IPAR, RUE, and HI were all affected by genotype. Biomass was more strongly correlated with RUE than n-ary sumation IPAR. Even among the highest yielding genotypes, values for functional yield drivers (biomass and harvest index) differed significantly, indicating that high yields could be achieved by differentially manipulating these underlying traits. However, when considered for all genotypes, only HI exhibited a significant positive correlation with yield. Boll production and intra-boll yield components were also affected by genotype. When considered across upland genotypes, lint per boll, lint per seed, and lint percent were strongly associated with HI and lint yield, whereas boll mass and seed number per boll were not. We conclude that the genotypes evaluated in the current study achieve high lint production per boll and lint yields by manipulating different yield drivers. However, lint yield was primarily maximized through an increase in HI due to increases in boll production and within-boll distribution of biomass to fiber, not due to increases in total biomass production or boll size. Lint yield varied significantly across a diverse collection of cotton genotypes. Maximum lint yields were achieved by manipulating different functional yield drivers. Across all upland genotypes, harvest index was most strongly associated with lint yield. Harvest index was most associated with sympodial boll numbers, fiber per boll, and fiber per seed.