Effect of shading at different developmental stages of cotton bolls on cotton fibre quality

Sunlight is one of the most important factors affecting cotton yield and fibre quality. There are more rain at flowering boll-forming stages in Yangtze valley, and unsuitable cotton population structure in Huanghe River valley limiting the increase of yield and the improve of fibre quality. The effect of sunlight on growth of cotton in seedling stage has been systemically researched, but limited research on fibre quality and the development in flowering boll-forming stages reported. The objective of this study was to evaluate the effect of shading on cotton fibre quality using the cultivars Zhongmiansuo 41 and Lumianyan 18 with three shading stages：boll age of 0-20 days （treatment Ⅰ ）, boll age of 21-40 days （treatment Ⅱ ） and boll age from 41 days to boiling （treatment Ⅲ ）. The results showed that the maximum fibre length of cotton was decreased and the elongation period was increased by shading. Fibre length was the maximum of CK at the boll age of 25 days without shading, while that of treatment Ⅰ at the boll age of 35 days, and that of treatment Ⅱ at the boll age of 30 days, but that of treatment Ⅲ also at the boll age of 25 days. Fibre gauge tenacity and maturity were both decreased, but fibre fineness was increased under shading at different stages. Treatment Ⅱ was the most effective one affected fibre development and was significantly different from CK, while treatment Ⅰ and treatment Ⅲ had less effect on fibre development. All the trends of the cotton fibre characters changed under shading were similar between two cultivars.