Abstract: After 60 years of research and production practice, China not only has established an intensive farming based technology system of cotton cultivation with distinctive Chinese characteristics, but also has founded a relatively complete theoretical system for China cotton cultivation. Such a theoretical system of cotton cultivation has made important contributions to enable China to be the first major cotton producing country in the world. Boll-setting optimization theory is the core of the theoretical system for high-yielding and fine-quality cotton production in China. The establishment, main contents and prospects of the boll-setting optimization theory are reviewed in this paper. Fiber yield and quality are a function of boll setting, which is significantly affected by boll-setting period, spatial position of the bolls, and the physiological state of the cotton plant. Optimization of cotton fruiting can be realized through formation of more bolls at the best boll-setting period, and in the best spatial position in a cotton plant with the most healthy physiological state. Peak boll-setting period is a stage with high photosynthetic efficiency for a cotton plant. Cotton fruiting can be further improved by synchronizing the periods of high photosynthetic efficiency of leaf canopy, peak boll-setting and ample light and heat resources. To optimize cotton fruiting, it is necessary, on the one hand, to stabilize or increase both the biological yield and economic index and on the other hand, to simultaneously increase the number of bolls per unit area and boll size through coordinating cultivar, environment and cultivation measures based on the dry matter accumulation and distribution features of high-yielding cotton. Photosynthetic products are the material basis that determine cotton yield. Dry matter accumulation at different growth stages directly affects boll setting in cotton. Optimization of cotton fruiting requires the maintenance of a higher dry matter accumulation after full bloom throughout the boll opening stage and a relatively high harvest index. It also requires configuration of an ideal plant architecture and optimal crop population structure through proactive and anticipatory control of cotton ontogeny. Maturity performance is termed as senescence performance of a cotton plant during boll opening. It includes performances of normal maturity, late maturity and premature senescence performance, respectively. Disorders of sink and source, as well as root and canopy often decreased root-sourced cytokinin levels and increased abscisic acid content, which might lead to early or delayed senescence-associated gene expression, finally leading to the formation of abnormal maturity performance (late maturity and premature senescence). To optimize the boll setting, it is necessary to well coordinate the relationship between the sink and source, root and canopy to realize the normal maturation of cotton plants. The establishment of boll-setting optimization theory not only promotes the development of science and technology of cotton cultivation in China, but also provides a strong theoretical support for the healthy development of China's cotton industry. It is believed that boll-setting optimization theory will remain the core of China’s theoretical system for high yield and quality cotton cultivation in the future. However, with the adoption and development of simplification, mechanization, sustainable and green production technology, cotton fruiting optimization theory will also experience further changes and development to better support the development of China's cotton production.

Key words: cotton , optimization of boll-setting , high yield , fine fiber quality