Optimization of cotton variety registration criteria aided with a genotype-by-trait biplot analysis.

China is one of the largest cotton producing countries in the world thanks to high yields, on which a variety registration system has mainly focused, so that a lack of quality is nowadays acknowledged as a weak point of the cotton industry in that country. The objective of this study was to check the hypothesis that bias in cultivar selection in favor of yield has been maintained through the application of an imperfect selection index (SI), but that a better outcome is possible. Our demonstration is based on an analysis of the data from ten years of cotton variety trials using genotype-by-trait biplots, implemented both for the cultivar selection index (SI) currently applied in China and for an adjusted selection index (ASI) that more effectively took into account the antagonism between yield and quality traits.

[Ecological regionalization of cotton varieties based on GGE biplot].

By using the heritability-adjusted GGE biplot analysis method, and taking the trial sites Anqing, Nanyang, Huanggang, Jingzhou, Wuhan, Xiangyang, Changde, Yueyang, Nanjing, Nantong, Yancheng, Jiujiang, Jianyang, Shehong, and Cixi as the representative cotton-planting areas in the Yangtze River basin, the ecological regionalization of cotton varieties in the basin was made based on the lint cotton yield, and the regionalization results were adjusted by the information ratio (IR) method, aimed to provide scientific basis for the selection of cotton varieties in the cotton-planting areas of the basin. The cotton-planting areas in the Yangtze River basin could be divided into three ecological regions, i.e.

Response of the enzymes to nitrogen applications in cotton fiber (Gossypium hirsutum L.) and their relationships with fiber strength.

To investigate the response of key enzymes to nitrogen (N) rates in cotton fiber and its relationship with fiber strength, experiments were conducted in 2005 and 2006 with cotton cultivars in Nanjing. Three N rates 0, 240 and 480 kgN/hm(2), signifying optimum and excessive nitrogen application levels were applied. The activities and the gene expressions of the key enzymes were affected by N, and the characteristics of cellulose accumulation and fiber strength changed as the N rate varied.

[Modeling of cotton boll maturation period and cottonseed biomass accumulation].

Field experiments with different maturity cotton cultivars and sowing dates were conducted at different sites to quantitatively study the effects of cultivar characteristics, weather conditions (air temperature and solar radiation), and crop management variable (N application rate) on the cotton boll maturation period and cottonseed biomass accumulation. The cotton boll maturation period was simulated by using the scale of physiological development time. Based on the hypothesis of sink-determined, the cottonseed biomass accumulation model was then developed.

[Effects of air temperature on enzyme activities of cotton plants related to saccharide metabolism of cotton fiber].

Taking two cotton cultivars with different fiber strength (KC-1, average fiber strength 35 cN x tex(-1); and AC-33B, average fiber strength 32 cN x tex(-1)) as test materials, a field experiment with two planting dates (25 April and 25 May) was conducted in Nanjing of Jiangsu (lower reaches of Yangtze River Valley) and Xuzhou of Jiangsu (Yellow River Valley) to study the dynamic changes of plant sucrase, sucrose synthase, sucrose phosphate synthase, and beta-1,3-glucanase activities during the development of cotton fiber at different air temperatures and their relationships with fiber length and strength. In the development period of fiber elongation, sucrase and beta-1,3-glucanase activities were higher; while during the period of fiber thickening, sucrose synthase and sucrose phosphate synthase activities increased rapidly and were high, but sucrase and beta-1,3-glucanase activities had a rapid decrease. The higher sucrase activity in fiber elongation development period favored the fiber length development, while the rapid increase of sucrose synthase and sucrose phosphate synthase and the rapid decrease of sucrase and beta-1,3-glucanase activity favored the development of fiber strength.

[Roles of nitrogen fertilization in regulating the physiological bases of fiber specific strength formation in cotton bolls bloomed at different dates].

To study the roles of nitrogen fertilization in regulating the physiological bases of fiber specific strength formation in cotton bolls bloomed at different dates (July 15, July 25, and September 10; expressed as PSB, SB, and AB, respectively), field experiments were conducted in two sites with different ecological conditions, i.e., Nanjing (middle lower reach of Yangtze River Valley) and Xuzhou (Yellow River Valley).

[The inheritance of an ultra-dwarf plant mutant from upland cotton].

The inheritance of an ultra-dwarf plant mutant from upland cotton (Gossypium hirsutum L.) was studied, which showed that the mutant was controlled by single recessive quality gene. This gene was denominated as du tentatively.