Analysis Of Genetic Effects And Heterosis For Main Economical Characters In Transgenic Insect Resistant Cotton (G.hirsutum L)

It is very effective to control the damage of cotton bollworm (Heliothis armigera) and other insects belong to Lepidoptera for the extensive utilization of transgenic insect resistant cotton, which is very important for the stablization and development of the cotton production in China. Up to now, there were more than 30 transgenic insect resistant cotton cultivars had been derived commercially in China, and more than hundreds cotton cultivars or hybrids with insect resistant genes were taking part in differnrt level of the regional cultivar tests in cotton production area, and the acreage of the transgenic insect resistant cotton had reached to 2/3 of the total cotton growing area in China. So it was very important for the breeding of the transgenic cotton to carry out the basic research works on the inheritance of the transgenic insect resistant cotton. Nine Bt and non-Bt cotton parents and their 36 F₁ combinations were analyzed for four yield traits, lint yield, bolls per plant, boll weight and lint percentage, as well as the fiber quality traits in two year's field experiment, using the genetic model of additive-dominance with environmental interaction effects and additive-dominance additive X additive with environmental interaction effects, respectively, and the genetic variant components and genetic effect correlations, as well as the heterosis, of the transgenic insect resistant cotton were estimated in this paper. The main results of research were as follows:1. All the yield traits of the transgenic insect resistant cotton were mainly controlled by the additive and dominant effects. Among them, the dominant effects were leading in the lint yield, boll weight, and lint percentage, while bolls/plant was a additive one on other hand. In addition, there were some interaction effects between genes and environments for bolls/plant and lint percentage. The general heretability in the broad-sense of lint yield, boll weight, and lint percentage was obviously larger than that of the interaction heretability in the narrow sense, but the interaction heretability in the narrow sense of bolls was larger on the other hand.2. The residual effects of fiber quality traits for the transgenic insect resistant cottonwas larger, especially for the micronaire and 2.5% staple length (>50%). There was much different about additive, dominant and interaction effects for each fiber quality traits, and the additive and dominant effects of micronaire and fiber strength were significant, but the AXE and D X E interaction weren't significant. On the contrary, the additive and dominant effects for elongation and uniformity weren't significant, but the AXE and DXE interaction were significant. The additive effects for 2.5%length was insignificant, and the dominant effects for 2.5% staple length was significant, and the AXE and DXE interaction were significant. In addition to additive and dominance effects, the additive X additive epistatic effects or interaction was significant for most of fiber quality traits.3. The genetic correlation analysis showed that the genotype and phenotype correlation for yield and bolls/plant of the transgenic insect resistant cotton were large, and their values were almost the same. The additive correlation between yield and bolls/plant were significant, as well as boll weight and lint percentage, and the values of additive correlation between lint yield and bolls/plant were large, as well as lint yield and lint percentage. Only the genotype and phenotype correlation of staple length and fiber strength in transgenic insect resistant cotton were very significant, and the dominant correlation between staple length and fiber strength was very significant. Genetic correlations between yield traits and fiber quality traits of the transgenic insect resistant cotton were estimated. The result indicated that the addition correlation between lint yield and fiber strength was very significant, the same as the positive addition interaction correlation. The positive genotype and phenotype correlation of bolls/plant and staple length were very significant, and the addition and dominant correlation was also very significant. The addition and dominant correlation, and addition interaction correlation of lint percentage and fiber strength were also significant or very significant.4. The F2 genotypic value and their heterosis were analyzed and forecasted from the data in the parents and their F|. The result of yield traits indicated that the average heterosis over mid-parent in F2 of the transgenic insect resistant cotton were4.0%, 5.1%, -1.3% and 3.2% for yield, boll per plant, boll weight and lint percentage, respectively, and that over the better parent were -7.3%, -6.0%, -4.2% and -0.5%, respectively. While the results for fiber quality traits indicated that the average heterosis in F2 of the transgenic insect resistant cotton over mid-parent were -0.8%> -2.9%, 1.0%, -8.5% and 0 for staple length, fiber strength, micronaire, elongation and uniformity, respectively, and that over the better parent were-2.2%, -5.6%, -0.8%, -13.7% and-1.3%, respectively. So there was some negative heterosis in yield traits and fiber traits in F2 of transgenic insect resistant cotton, which led to the limitation for utilization of F2. 5. The results of genetic analysis for yield and fiber quality traits of transgenic insect resistant cotton indicated that there was some potential to improve the yield traits of the transgenic insect resistant cotton using crossing breeding programs. However, there were some difficulty in improving the fiber quality by the cross breeding program, and only a limited effective had been made. For the utilization of heterosis among the transgenic insect resistant cotton, it is very important to consider the yield and fiber quality, as well as their genetic correlation, of two parents which have been used in hybrid, in order to develop a superior heterosis transgenic insect resistant hybrid cotton.