Analysis Of Genetic Effects And Heterosis For Seed Quality Characters In Upland Cotton (G.hirsutum L)

Cotton is one of the most important economic crops.Cotton fiber is its main purpose,cottonseed is the by-product of cotton.Most of the cottonseed used as the feed for ruminant animals;like cattle,coat and so on,or as fertilizer,and it has been utilized fully.In fact,cottonseed has high value both in nutrition and research. Cotton seed kernel contains protein(30%～45%),oil(25%～40%),gossypol (about 1%),so it is a economic crop both in oil and protein as well.On the other hand,studying cottonseed is also for fiber studying,as fiber is developed from the superficial cells of the cottonseed,the quality of the fiber is mostly depended on the nutrition supply from cottonseed.In addition,cottonseed contains all of the genetic message,its sowing quality is closely related to the plant growth and cotton yield.So the genetic research on cottonseed has double meanings both in theories research and practical application.In present study,we used 10 parents and their 32 F₁ and 33 F₂ combinations to analyze six physical properties and six chemical properties in one year's field experiment,using the genetic model for diploid seed(concluded embryo nuclear genes,cytoplamic genes,maternal nuclear genes)to estimate the genetic variant components and genetic effect correlations,as well as the heterosis of the upland cottonseed.The main results of the studies were as follows:(1)Building the regression equations for analyzing protein content by NIRS,the parameters of RSQ is 0.933,1-VR is 0.929,SEC is 0.623,and SECV is 0.638. The results of high in RSQ and 1-VR,and low in SEC and SECV reflect that the regression equation will be good for analyzing the contents of protein,oil and gossypol in cotton kernel powder.(2)The performance of the physical traits in upland cotton seed were simultaneously controlled by the genetic effects from the diploid nuclear genes and maternal plant nuclear genes,except the kernel percentage.The kernel percentage was controlled by the genetic effects of embryo nuclear genes, cytoplasmic genes and maternal plant nuclear genes.The dominance effect of embryo and maternal plant genes were important in the performance of fuzzy seed index and naked seed index,especially the maternal dominance effect.The embryo dominance effect and the maternal additive effect were equal important in kernel/hull.The rest effect was significant in kernel percentage.In a whole, maternal gene effects were more important than another effects in the performance of physical traits.The high value in general heritability and low value in narrow heritability showed their breeding value is lower.(3)The results of the varinance of the nutritional traits showed that there were no cytoplasmic effect,controlled by embryo and maternal nuclear genes.The additive and dominance effects were equal important in the 6 nutritional traits of cottseed,especially the dominance effect.Maternal nuclear effect is more important.The high values both in additive and dominance effects and in general heritability and narrow heritability indicated the higher efficiency in breeding improvement for nutritional traits of cottonseed.It is possible to select new cultivars with good cottonseed nutrition qualities.(4)The coefficient of correlation between seed physical traits showed there were positive correlation ship between fuzzy seed index and naked seed index,fuzzy seed index and kernel index,kernel index & kernel percentage,and kernel index & kernel percentage,but negative correlation between kernel/hull & kernel index.The coefficient of correlation between seed chemistry traits showed there were positive correlation between gossypol content & gossypol index,oil content & oil index,protein content & protein index,gossypol content & oil content,gossypol content & oil index,gossypol index & oil content,and gossypol index & oil index.There were negative correlation between gossypol content & protein content,gossypol content & protein index,gossypol index & protein content,gossypol index & protein index,oil content & protein content, oil content & protein index,oil index & protein content,and oil index & protein index.All these showed that it was possible to improve gossypol content and oil content,but difficult to improve the gossypol content and protein content or protein and oil content at same time.(5)The coefficient of correlation between seed physic traits and chemistry traits showed that the correlations were same between naked seed index and chemistry components and/or kernel index and chemical components were same.Because of the negative maternal dominance correlation,the phenotype and genotype correlation between these two cottonseed physical traits with gossypol content, gossypol index,oil content were negative,but their embryo dominance correlation was positive.The correlation between those physic traits and protein content were positive because of the positive maternal dominance correlation. All these results showed to improve the naked seed index or kernel index would result to low value in gossypol content,oil content and gossypol index.But these phenomenon could be improved by selection of seed genotypes.The high correlation between physic traits and protein content,protein index indicated that the maternal effect was important in the improvement of cotton seed quality.The correlation between fuzzy seed index and protein index was positive,so we could select high protein according to the fuzzy seed index.(6)The results of average heterosis in F₂ population on nutrient quality characters of cotton seed indicated that positive heterosis especially high maternal heterosis was observed in gossypol content.Although positive heterosis was observed in oil content and gossypol index,negative heterosis were observed in protein content and oil index,the value of heterosis were very low.The heterosis of protein index was negative,there were 32 combinations with negative heterosis among total 33 combinations and with high mean value(up to-16%).Because of the maternal negative heterosis,the embryo positive heterosis may enhance the seed protein index in some extent.The average heterosis in F₂ population were not observed in fuzzy seed index,naked seed index,kernel index, kernel/hull,which influented by the negative maternal hetersis.The embyto heterosis in naked seed index were positive,which advance the heterosis to some extent.The positive effects of embyto,cytoplasm and maternal made the positive heterosis in kernel content,but all the value is low.(7)For fuzzy seed index,negative values in mid-parent heterosis and transgressive value were observed both in F₁ and F₂,which indicated that there was no heterosis on physical properties.However,there were mid-parent heterosis of naked seed index,kernel index and kernel/hull in F₁.Kernel percentage in F₁ exhibited the mid-parent and the transgressive heterosis,while kernel percentage in F₂ also exhibited the transgressive heterosis with lower value.For nutrient properties,the mid-parent and the transgressive heterosis were observed in protein content and index in F₁ but not in F₂,which implied the low utilization value of them.Gossypol content in F₂ exhibited the mid-parent and the transgressive heterosis but not in F₁.Oil content and gossypol index only exhibited the mid-parent heterosis in F₂ with low value,which indicated the utilization value of them was lower.Heterosis of oil index was not observed.