Heterosis Of F₁Reciprocal Crosses, Performance And Potential Of F₂and Seed Reproductive Efficiency On Hybrids Cotton

Agronomic characters and economic heterosis of F1hybrid seedlings from obverse cross (Bll×4-5, Bll×119-1) and inverse cross (4-5×B11,119-1×B11) were evaluated in this project. Also, the potential value of of F2and reproductive efficiency hybrids of "huazamian H318" were studied in the research for the further theoretical and practical basis to extend the two varieties. The main results were as follows:1. Agronomic traits at seedling stage of F1hybrids:The cotyledon size of F1hybrids form obverse cross was significantly larger (P<0.05) than that of inverse crosses, which was obviously affected by maternal inherited effects. The growth of the first three true leaves showed that the development of the first leaf could be related to the hybriding mode, which also affected by female parents. So the development of the first leaf was mainly dominated by nuclear genome, and also may be influenced by maternal effects on some level. There was no significant difference of in seedling height and leaf number from main stem between obverse cross and inverse cross, showing that the heredity of the two traits may be controlled by the nuclear genome of both two parents.2. SPAD value of the function leaves at different growth stages:SPAD value can reflect the chlorophyll content. SPAD value of hybrid F1between obverse cross and inverse cross of two cultivars at different growth stages did not show significant difference.3. Yield traits and its components between obverse cross and inverse cross:The cotton yield and lint yield of obverse cross from "huazamian H318" were305.6and124.9kg/666.7m2respectively, while that of "huazamian4hao" was313.8and128.0kg/666.7m2. The cotton yield and lint yield of inverse cross hybrid F1of "huazamian H318" were303.5and123.6kg/666.7m2respectively, while which were310.3and125.9kg/666.7m2from inverse cross hybrid F1of "huazamian4hao". The yield between obverse cross and inverse cross didn’t show significant difference, but their mid-parent heterosis and over-parent heterosis were obvious. The yield between hybrid F1(no matter obverse hybridized or inverse hybridized) from two cultivars and the control did not show significant difference. So both two varieties show potential value in agricultural production. However, MH (mid-parent heterosis), AH (over-parent heterosis) and CH (over-standard heterosis) of the boll weight and lint index from obverse cross performed better than those of inverse cross.4. The fiber quality between obverse cross and inverse cross:The differences of fiber quality with five indexes obverse cross and inverse cross hybrid did not show significant diference. Five indexes of fiber quality-fiber length, uniformity, micronaire value, elongation, and strength, from obverse cross hybrid F1of "huazamian H318" were29.87mm,84.23%,5.30,6.30%and29.97cN/tex respectively, while inverse cross hybrid F1were29.84mm、84.13%、5.27、6.23%and30.77cN/tex. The five index of obverse hybrid of "huazamian4hao" were30.80mm、84.97%、5.29、6.20%and30.47cN/tex, while negative hybrid F1was30.74mm、84.53%、5.29、6.20%and30.67cN/tex. The fiber quality of both obverse cross and inverse cross hybrids had a little bit heterosis when compared to the control.5. Correlation analysis of agronomic traits:There was significantly positive (P<0.01) correlated relationship between cotton yield and weight per boll. The correlated relationship between cotton yield and lint percentage was significantly positive (P<0.05). Weight per boll was significantly positive (P<0.01) correlated with lint percentage and significantly negative (P<0.05) correlated with the number of bolls per plant.The number of bolls per plant was significantly negative (P<0.05) correlation relationship with lint percentage. There was no correlated relationship between cotton yield and fiber quality. During fiber mature stage, the SPAD value of leaves and the bolls number per plant has significantly positive (P<0.05) correlation, indicating that during the fiber mature period, the higher SPAD value will company with the slower aging of the leaf which resulting in the increasing of bolls per plant. Fiber length and micronaire value has significantly positive (P<0.05) correlation with strength. Elongation was significantly negative (P<0.01) correlated with strength.6. Performance and potential of "huazamian H318F2":Cotton yield and lint yield of F2were295.2and117.5kg/666.7m2, respectively. Cotton yield of F2decreased by3.40%and lint yield decreased by5.92%when compared to F1. Compared with the control, cotton yield of F2was reduced by2.51%and lint yield was reduced by4.47%, but all the differences didn’t reach the significant level. Only fiber strength of F2was significantly lower (p<0.05) than F1, while other indexes of fiber quality had no significant difference. However, there was no significant difference between F2and the control on fiber quality. For insect resistance, about75%of F2population inherited insect resistance character of the parents which can resistant cotton ball worm, but the rest plants did not show insect resistantance, indicating that the heredity of insect-resistant was controlled by one dominant allele. All these data suggested that "Huazamian H318F2" had potential in agricultural production.7. Reproductive efficiency of "huazamian H318":Hybrid seed production from non-insect-resistant plants as female parents (obverse cross) was lower than using insect resistant plants as female parents (inverse cross) on the same field conditions. The highest seed yield (74.9kg/666.7m2) was achieved from inverse cross when plants density was1300plants per666.7m2, while seed yield was lowest (51.6kg/666.7m2) from obverse cross at density of1300plants per666.7m2. The seed index from inverse cross was lower than the one from obverse cross, however, the seed germination rate between obverse cross and inverse cross did not show significant difference.