Genetic Analysis Of Heterosis And Other Traits In Uplang Cotton

Cotton is produced as raw material for the textile industry and is considered to be a high value crop. During the past decades, the hybrid cotton was greatly planted by the Yellow River valley and the Changjiang River valley. Therefore, the method for mating hybrid cotton is necessary for establishing the parental core. In this study, nine parental lines of upland cotton, collected from germplasms of the Yellow River valley, were evaluated byGardner and Eberhart's diallel analysis for combining ability, heterosis and other genetic parameters for cotton yield, fiber quality et al. Furthermore, genetic distances from molecule and phenotypic data were estimated. Comparison of phenotypic and molecular distances related with heterosis, combining ability from Gardner and Eberhart's diallel analysis, and F₁ performance was analyzed to predict heterosis. Based on the above genetic distances and leaf morphology among the nine parental lines, the present study also reported the quantitative genetic analysis of time of flowering, leaf morphological traits and premature senescence of leaf from the intraspecific crosses using joint segregation analysis or generation mean analysis.1. 45 diallel entries including nine parental lines and their 36 crosses were evaluated by Gardner and Eberhart's diallel analysisâ…¡andâ…¢. For a majority of traits, variety, heterosis, crosses, general combining ability (GCA) effects were significant, and average heterosis and variety heterosis effects was not significant, indicating additive effects were important for heterosis of upland cotton. Estimates of variety, GCA and variety heterosis effects showed Zhongmiansuo 41, Handan 109 and Luyanmian 28 among nine the parental lines were the relative best for heterosis of yield. According to the results of population midparent heterosis and population high-parent heterosis, a majority of the performances of F₁ were between their double parental lines, but proportion of high-parent heterosis, especially positive significance, was relatively less. The genetic relationship among yield and fiber quality had some changes after hybrid occurred among the parental lines. According to the above results, the utilization of heterosis is feasible for several traits, and hybrid cotton cultivars for breeding in upland cotton should increase no. of total bolls, retain suitable boll weight lint%, and cooperatively improved fiber quality.2. This study was also undertaken to determine the relationship between parental distances estimated from phenotypic traits and molecular markers with heterosis and F₁ performance. The positive correlation between phenotypic and molecular distances was highly significant. Negative correlations between molecular and phenotypic distances with several traits of F₁ were highly significant. Mean phenotypic and molecular distances were significantly correlated with GCA and variety effects for most of traits with negative. According to the results, the corrections were negative between phenotypic or molecular distances with a majority of heterosis traits.3. This paper presents a study of the genetic control for time of flowering in Kang3×Chaoji463 and Handan109×Ji98 crosses obtained from different early-maturity parental lines. In each cross, multiple generations including P₁, F₁, P₂, B₁, B₂ and F₂ were evaluated under two natural field conditions. The data on time to flowering in the F₂ populations had a continuous distribution but deviated from normality. A joint segregation analysis (JSA) revealed that time of flowering in upland cotton was controlled by a mixture of an additive major gene and additive-dominant polygenes. The first- and second-order genetic parameters were all calculated based on the mixture of major gene and polygenes inheritance models using JSA. These results suggested that there was considerable genetic diversity and complexity in days to anthesis in upland cotton. This variation can be used to formulate the most efficient breeding strategy and to design cotton for a particular environment.4. Genetic manipulation of leaf architecture may be a useful breeding objective in cotton (Gossypium spp.). The present study firstly reported quantitative genetic analysis of leaf traits from two intraspecific crosses of inbred lines in upland cotton (Gossypium hirsutum L.) viz. Kang3×Chaoji463 and Handan109×Ji98. Six leaf morphological traits (leaf area, leaf perimeter, main lobe length and width, petiole length, and main lobe length/width ratio) were recorded from multiple generations (P₁, F₁, P₂, B₁, B₂, and F₂) in the two crosses. Generation mean analyses were conducted to explain the inheritance of each leaf morphological trait. The six-parameter model showed a better fit to an additive-dominance model for leaf area, main lobe width, petiole length, and main lobe length/width ratio in the two crosses, suggesting the relative importance of epistatic effects controlling leaf morphology. A simple additive-dominance model accounted for the genetic variation of the main lobe length in the Kang3×Chaoji463 cross. Different models were selected as appropriate to explain leaf perimeter in the two crosses. The estimated minimum number of genes controlling each leaf morphological trait ranged from 0-2 for both crosses. Moreover, the sums of the minimum number of genes controlling leaf morphology were 6 and 2 in the Kang3×Chaoji463 and Han109×Ji98 populations. respectively. Most data suggested that there existed a substantial opportunity to breed cottons that transgress the present range of leaf phenotypes found.5. According to the changes of leaf Chlorophyll (SPAD) before and after the flowering time in nine cotton lines, the reductions between leaf Chlorophyll at 35 days after the flowering and at flowering was used as one of the indicators of senescence. Another measurement of stay-green was an independent visual estimation of the retention of the green-area for leaves at 35 days after flowering on a 1 to 5 scale. Generation mean analyses were conducted to explain the inheritance of leaf senescence for multiple generations (P₁, F₁, P₂, B₁, B₂, and F₂) in the Kang3×Chaoji463 cross. The results according to the SPAD and scale were relative consistent, both showing additive effects controlled the genetic of leaf senescence without dominance and epistatic effects.