Study On The Genetics Of Boll Development And Its Relationship With Yield Quality In Land Cotton With Different Density

As the main economic product in cotton production,cotton boll is composed of boll shell,fiber and cotton seed.The yield and quality of cotton fiber are closely related to the genetic and environmental factors of the variety,and the appropriate density helps to improve the ventilation and light penetration of cotton plants.In this experiment,seven land cotton parents and 21 orthologous combinations were tagged at peak flowering under three density conditions:high density(2.4×10~5 plants/hm~2),medium density(1.8×10~5 plants/hm~2)and low density(1.2×10~5 plants/hm~2),and thereafter at early(5 and 10 d),middle(15,20,25 and 30 d)and late(40 and 50 d)stages,respectively.Samples were taken to determine the bell shape and dry weight of each component,and the growth trends and characteristic values were analyzed by DPS,and the genetic variance,heritability,correlation and effect values were predicted by ADM and developmental genetic model with environmental interactions.The main findings were as follows:1.The dry weight and boll shape traits of each boll component accumulated at different rates,but the growth trends were basically the same.Among them,the maximum value can be reached in 30 days for boll shell.The growth of fiber and dry matter of cotton seeds accelerated in 30-50 days and increased almost linearly.Volume,longitudinal diameter and transverse diameter grew faster from 0 to 25 days and fluctuated within a certain range from 25 to 50 days.Comparing the dry weight and boll shape traits of each boll component at different densities,the accumulation of boll shell was the greatest at low densities,and the maximum accumulation rate appeared the latest;the fast growth period lasted the longest at high densities for cotton seeds and fibers,and the accumulation was the greatest at medium densities.There were highly significant or significant differences in the maximum accumulation of volume and duration of the fast-growth period among the densities,and low density>medium density>high density;the maximum accumulation of boll longitudinal diameter was not significantly different between high density and medium density,and was highly significantly lower than that of low density;the characteristic values of boll transverse diameter were not significantly different among the three densities.2.Developmental genetic analysis of the boll traits showed that the boll traits were mainly affected by unconditional and conditional dominance with environmental reciprocal variance,indicating that there might be a greater heterosis advantage under different density or environmental conditions.Traits such as single boll weight,coat score,maturity,neatness and Macron value were influenced by maternal genotype,and there was a greater heterosis advantage for most yield and quality traits,but the heterosis advantage was inconsistent under different density conditions.The results of heritability analysis showed that most of the boll traits and each component of dry matter had large broad-sense heritability and broad reciprocal heritability during growth and development,while there were large unconditional narrow-sense heritabilities in the middle and late stages,while the narrow-sense and broad-sense heritabilities of quality traits were larger and the heritabilities of yield traits were all lower,thus having a better indirect selection effect on yield traits through boll traits.3.Genetic correlations showed that there were significant additive correlations between boll shell dry weight,fiber dry weight,boll volume,boll longitudinal diameter and boll transverse diameter in the middle and late stages of boll development,and significant maternal correlations between fiber dry weight in each period,and most of them could be expressed in phenotypes,so that the final performance of these traits could be selected by the performance after the middle stage;correlations between boll shape and each component dry weight and yield and quality in different periods of land cotton The correlations between dry weight of shell,boll volume,longitudinal diameter of single boll,transverse diameter of boll and fiber length,maturity,specific strength and elongation in most periods were significant additive and genetically and phenotypically positive,and fiber dry weight and single boll weight and neatness in most periods were significant maternal,genetic and phenotypic correlations,and cotton seed dry weight and single boll weight,fiber maturity and neatness were significant additive or maternal and genetically and phenotypically positive,Therefore,selecting materials with slightly thicker hulls,larger boll length,boll diameter and boll volume would help to improve most of the quality traits,while fiber dry weight and cotton seed dry weight had less influence on other yield quality traits except for single boll weight and neatness.4.The predicted values of boll dry weight according to different densities at different periods showed that 15-16.Card at high and low densities,and 4-12 at medium densities significantly increased progeny boll dry matter accumulation,and Xinlu Zhong51 at three densities could significantly reduce progeny boll dry weight of crosses.The predicted values of fiber dry weight at different densities showed that Xinlu Zhong37 was significantly more effective at the three densities,and 15-16.Card was significantly less effective at the three densities.The predicted values of dry weight of cotton seeds at different densities showed that Xinluzhong 37 was significantly synergistic at high density,69-8 was significantly synergistic at medium and low densities,and Xinluzhong 51,49-13 were synergistic.The predicted values of boll volume at different densities showed that 15-16.card could increase the progeny boll volume at high and low densities,more positive values were predicted for 4-12 at medium density,and more negative values were predicted for AL15-11 at all densities.The predicted values of longitudinal boll diameter at different densities showed that AL15-11 at high density,4-12 at medium density,and 15-16.card at low density could significantly increase the longitudinal boll diameter of progeny,and Xinlu Zhong51 at all three densities could reduce the longitudinal boll diameter of progeny.According to the predicted values of boll diameter at different densities and periods,4-12 could significantly increase the boll diameter of hybrid progeny at three densities,and Xin Lu Zhong51 could significantly decrease the boll diameter of hybrid progeny.