The Comparing Analysis Of The Genetic Effect Of Main Characters Among Different Crossing Type In Cotton

Cotton is one of the important economic crops. It is the permanent goal of breeder to breed new high-yield and high-quality varieties of cotton. The utilization of heterosis is a new way to improve the qualitative and yield of cotton fiber. On the basis of last two years, in this experiment five upland cottons as maternal plants, six upland cottons (one is brown cotton) and one sea island cotton as paternal plants were crossed in NCII heredity copulation design. The heterosis appearance of F1 component and the correlation to the genetic distance of parents in the different hybrid type were studied. Next year, four representative components were selected : Naturally colored cotton×white cotton, sea island cotton×upland cotton, and two upland cotton×upland cotton. The genetic effects of the main characters were calculated by the method of generation mean analysis, the genetic mechanism of heterosis were probed into. The color genetic mechanism and genetic correlations of brown cotton were analyzed. The findings are showed as follow:1. The contrast of heterosis between upland component and island cottonAll of yield traits have high heterosis in upland component and island component. Among island component boll number's mid-parental heterosis is higher than among upland component. Boll weight, lint yield per plant and lint percent among island component are as same as upland cotton. On super-parental heterosis, all of yield traits have advantage among upland cottons, boll number has advantage among island cotton.About quality character, the superiority of 2.5%span length is the most evident. Its mid-parental heterosis and super-parental heterosis are high. The mid-parental heterosis among sea island cottons is high than upland cotton. It is showed that fiber length has evident super dominance. Breaking strength has superiority too.2. The correlation of the heterosis and the genetic distance of parentsAbout the heterosis and the genetic distance of parents, it is showed that the correlation degree is different in different traits. the coefficient of correlation between mid-parental heterosis and the genetic distance of parents, about fruit nodes,boll number,lint yield,2.5% span length,fiber uniformity,breaking strength is significant or extremely significant positive correlation. Lint percent,fiber elongation rate is negative correlation.. The coefficient of correlation of bolls between super-parental heterosis and the genetic distance of parents is significant positive correlation. That of lint percent,breaking strength,fiber elongation rate is negative correlation. Others aren't significant.3.The genetic effect analysis of filial generation of different crossing typeThe genetic effects among the fruit brunch number, boll number per plant and seed index are same in natural color cotton×white cotton, white cotton×white cotton, sea island cotton×upland cotton. The number of fruit brunches has marked dominance effect and dominance-dominance effect. Boll number and seed index are accord with additive-dominance-epistasis model. The additive effect is major. Boll weight and lint yield of plant are complicated. They are different in different crossing type and remain to be researched. Fiber length is accord with additive-dominance-epistasis model in all of crossed type, but additive effect is significant. The dominance-dominance epistasis is significant in sea island cotton×upland cotton.Fiber uniformity index is conformed to additive-dominance-epistasis model, additive, dominance and dominance-dominance epistasis are all significant. The appearance of macroniare value is different : it is conformed to additive-dominance-epistasis model in natural color cotton×white cotton, it is conformed to additive-dominance model in sea island cotton×upland cotton. The additive effect and dominance effect are significant.. Fiber elongation rate is conformed to additive-dominance-epistasis model, the additive effect is significant. Breaking strength's additive effect is significant in upland cotton×upland cotton and sea island cotton×upland cotton, in natural color cotton×white cotton there is the additive effect, but it isn't significant. The dominance effect is significant in sea island cotton×upland cotton .4.The correlation between heterosis and genetic effectFrom super-parental heterosis and its superiority source, the dominance effect and the epistasis lead to the heterosis. All of the the epistasis, dominance - dominance epistasis contribute most to heterosis. additive - additive epistasis take effect under the circumstance of additive effect existing, it has less contribution to heterosis. additive - dominance epistasis has no contribution to heterosis.5.Genetic analysis and correlation of colour trait of brown cottonBrown fiber'color was controlled by a pair of main gene, these genes are incomplete dominance to white gene. And it is modified by some minor genes. This gene system is Gai Junyi's major-gene and polygene inheritance system. White degree was positive correlation with boll number per plant, boll weight, lint yield per plant, lint percentage, 2.5%span length, uniformity, breaking strength except elongation rate.