Carbohydrate profiles during cotton (Gossypium hirsutum L.) boll development and their relationships to boll characters

The dynamics of non-structural carbohydrates (NSC) in various fractions of cotton boll might have significant impact on within-boll lint and seed yields. The objective of this research was to determine how NSC in the three fractions of cotton boll (the fiber, the seed, and the burfluctuated at various stages of development and assess whether there was any association between carbohydrate profiles and boll characters. Five upland cotton genotypes differing in boll size and its components were examined in 2011 and 2012. Boll samples were harvested at 10, 17, 24, 31, 38, 45, and 52 days post anthesis (DPA) and analyzed for glucose, fructose, sucrose and starch. The starch concentration in those fractions from all genotypes was characterized by a declining trend with a faster decrease during the first 24 DPA than during later stages of boll development in both years. The sucrose concentration in embryos increased up to 24 DPA and then declined down to a minimum at 38 DPA corresponding the beginning of embryo desiccation. Thereafter, the sucrose concentration increased linearly, to form a second peak observed at 52 DPA. No difference between two years was found for the kinetics of sucrose concentration in embryos. The sucrose, glucose and fructose concentrations in fibers presented as single-peak curves during fiber development with the maxima occurring at either 17 or 24 DPA, corresponding to the transition phase from primary to secondary wall formation or to the beginning of massive secondary cell wall formation. Boll characters (boll size, lint percentage, and lint mass per boll) were more related to the starch and sucrose changes in embryos than in fibers. Sucrose might withdraw from either seeds or fibers to burs by maturity.