Study On The Methods Artificial Engendering The High Showing Stigma Of Upland Cotton And Its Application In Cotton Hybrid Seeds Production

In the thesis, the experiments of methods of high showing stigma artificial engendering by using GA3 and its application in cotton hybrid seeds production had been designed to study the effects of GA3 on flowers and floral organs, boll formation and boll characters, and to compare the differences of yield and benefit of cotton hybrid seeds production. The feasibility of applying artificial engendering high showing stigma by using GA3 in cotton hybrid seeds production also had been expounded in the thesis. The conclusion of the thesis were as followings.1) The effects of GA3 on cotton flower and floral organs, boll formation and boll charactersBy spreading with GA3 of the concentration of 25～200 mg/kg on the buds, the stigma had been lengthened, sepals and corollas had been enlarged, the color of the corollas had been faded, while the stamens hadn't changed significantly, so the high showing stigma had been engendered. The treatment with GA3 had no significant influence on the pollination ability, and the vigor of the pistil and that of the pollen. While pollination efficiency had been reduced significantly if artificial pollination was not conducted. The result indicated that the pollination efficiency of self-cross could be reduced by the high showing stigma engendered with GA3 treatment.2) The approaches of engendering the high showing stigma of cottonThe result showed that there was a significant negative correlation between the length of stigma showing above stamens and pollination efficiency of self-cross. Generally, the length of stigma showing above stamens was longer than 8mm, the ratio of self-cross pollination was lower than 5%. This suggested that the length of stigma showing above stamens was longer than 8mm was the key to the technology of applying high showing stigma engendered by using GA3 treatment. According to the results, the approach of engendering high showing stigma by using GA3 was to spread buds with GA3 of the concentration of 100 mg/kg, the optimum treating time was 6 to 18 days after the buds visible.3) The feasibility of applying artificial engendering high showing stigma in cotton hybrid seeds productionThe two keys to assuring the quality of cotton hybrid seeds production were the length of stigma showing above the stamens (above 8 mm) and the self-cross retention (lower than 5%). According to our study, to assure the length of high showing stigma being above 8mm and the self-cross retention being lower than 5%, we need 23 WD(working days) for spreading the buds with GA3 two times, and covering the stigma with litter paper for prevention self-pollination, and manual assistant pollination,, which was 7 WDs/667m/less than that of normal manual stamens-removing method. This resulted the reducing of the cost of cotton hybrid seeds production to 10.26 yuan/kg, which was 6.27 yuan/kg less than that of normal manual stamens-removing method. The result suggested that applying the approach of artificial engendering high showing stigma by using GA3 in the cotton hybrid seeds production was feasible.The high showing stigma above 8 mm can be engendered dependably by taking a suitable approach. The method can be applied in cotton hybrid seeds production to get a purity of above 95% of cotton hybrid seeds, and to save the labor cost, and increase the seeds yield and benefit. The method was with great significance for cotton hybrid breeding and cotton hybrid seeds production.