Construction of optimum number of fruiting nodes benefit high yield in cotton population

High yield is the most important goal for cotton growers, but widely application of previous reported agronomic practices was difficult due to variations of locations, climate, and cropping system in Yangtze River area. It is desirable to find an universal index to indicate canopy structure and photosynthetic production states for high yield. Field studies with different planting densities, sown dates and nitrogen rates were conducted to detect the relationship between lint yield and number of fruiting nodes per hectare (FNN) during 2016 and 2017 cotton growth seasons. Across different cultivars and cultivation practices including sown dates, nitrogen rates, and planting density, the FNN was comparatively stable under highest yield, indicating the optimum FNN (290−320×104 nodes/ha) would benefit high yield formation. In 2018 and 2019, three FNN cotton populations (low, optimum and high) constructed by three nitrogen rates were designed to assess the canopy structure, photosynthetic production and final yield. The results showed that there were moderate plant height (conventional cultivar Sikang1: 101.7 cm–103.5 cm, hybrid cultivar Sikang3: 109.5 cm–110.1 cm), length of fruiting branch, bigger space for individual fruiting node, uniform vertical distribution of LA (the leaf area) and light intensity in cotton plants under optimum FNN. In addition, high leaf SPAD, highest leaf Fv/Fm, activities of SuSy, SPS, and SAI, uniform vertical distribution of dry matter and high ratio of dry matter accumulation in reproductive organs in cotton plants were found under optimum FNN condition. These results suggested that appropriate plant type and canopy structure could be constructed by building optimum FNN, and optimum FNN would promote photosynthetic capacity and dry matter accumulation in reproductive organs, and ultimately benefit the final yield. In addition, due to the comparatively stable FNN in high-yield cotton production across different cultivation practices and locations, FNN would be an key index to build high-yield cotton population.