Studies On The Cross Breeding For The High Heterosis Of Cotton Hybrids In Resistance To Pink Poll-worm And Its Applications

In 2004, cross combinations of hybrids were made by adopting upland cotton varieties as parental materials that include 2 sterile female parents, 3 female parents and 4 male parents with high yield or high quality or pink boll-worm resistance with different mechanisms following the way of North Carolina â…¡(NC â…¡). 22 materials were tested in total, "Eza No.1" was used as the control variety and another traditional upland cotton cultivar "Hkang No.1" as the reference at the same time. The test was made in accordance to the design of randomly grouped plots and repeated 3 times for studying some main economic and agronomic characteristics, physiological indexes, resistance to insects and diseases, heterosis of F₁ hybrids and the correlation between the main characteristics. Variance analysis was made for each index to compare the diversity among the materials. The main results were as follows:(1) The seed cotton yield of 8 F₁ hybrids were higher than that of the control "Eza No.1", the lint yield of 4 F₁ hybrids were higher than the control, and the percentages of yield increase varied from 1.27% to 21.96% and 0.98% to 18.15%, respectively. The seed cotton yield and lint yield of the 13th material were much higher than that of the control.(2) Among the yield components of the hybrid variety, the mature boll number accounts for a larger proportion, whereas the boll weight and the lint percentage are equivalent to or even lower than those of non-resistant hybrids and the control. Therefore the main cause that the insect resistant varieties have a higher output is due to mat they have higher resistance and more mature bolls.(3) The five indexes of fiber quality of the F₁ hybrids were as follows. The fiber length varied from 24.57mm and 28.20mm, the fiber uniformity was between 81.83% and 84.97%, the fiber elongation percentage was between 6.03% and 6.87%, the fiber strength changed from 23.43 cN/tex to 30.5 cN/tex and the Micronaire values of all F₁ hybrids, which varied from 5.23 to 6.23, were higher than the normal. The fiber quality of the insect resistant materials had no advantage over the control.(4) By evaluation of the percentages of the damaged seeds in the general environment, the results showed that the hybrids with the backgrounds of transgenic insect resistance (Bt/CpTI) had the lower percentages than that of the non-resistant varieties. The results of resistance to the Fusarium wilt showed that one material was tolerant and the others were resistant or high resistant.(5) The results of correlation analysis indicated that the mature boll number showed...