Research For Cytoplasmic And Restorer Gene Effects Of CMS-D2 In Upland Cotton

To investigate whether the sterile cytoplasm and recovery genes of G.harknessii cotton have an effect on seedling growth,leaf photosynthetic characteristics,anther fertility and ultimately yield and fibre quality traits in cotton.In this study,we used the maintainer line ZB[N（rfrf）]as the parent and crossed it with the restorer line ZBR[S（Rf Rf）]and with the sterile line ZBA[S（rfrf）]respectively.Then,after 10 generations of backcrossing with ZB[N（rfrf）]as the rotating parent,three genetically near-isogenic lines were created to maintain the ZB line of G.harknessii cotton,with the genotypes S（Rfrf）and N（Rfrf）and S（rfrf）respectively.In this study,the genotypes S（Rfrf）and N（Rfrf）were used to self-recover the sterile cytoplasmic recovery line SR[S（Rf Rf）]and the sterile cytoplasmic pure recovery line NR[N（Rf Rf）]of upland cotton,and NR and SR were self-reproduced,and the maintainer line ZB was self-reproduced to obtain NB[N（rfrf）].ZB was crossed with NR to obtain NH[N（Rfrf）],ZBA was crossed with NR to obtain SH[S（Rfrf）],and finally two sets of homozygous heterozygous and one homozygous heterozygous G.harknessii cotton recovery gene near-isogenic line materials NH[N（Rfrf）]and SH[S（Rfrf）],NR[N（Rf Rf）]and SR[S（Rf Rf）],NR[N（Rf Rf）]and NB[N（rfrf）],all five materials with nuclear genetic backgrounds from the maintenance line ZB were planted in 2020 in the Yellow River Basin cotton region（Anyang,Henan）and the Yangtze River Basin cotton region（Jiujiang,Jiangxi）,respectively.Differential significance and correlation analyses were conducted on seedling growth traits,leaf photosynthetic physiological parameters at full reproductive period,anther development status,yield and its constituents as well as fibre quality traits,with a view to elucidating the effects of sterile cytoplasm and recovery genes in G.harknessii cotton and their use in heterosis breeding.In this study,the effects of the sterile cytoplasm and recovery genes on the main traits of land cotton were systematically investigated,and the results are of great significance for the selection and improvement of cotton cytoplasm-sterile"three-line"hybrids.The results of the study are as follows:The results of the effect of sterile cytoplasm in G.harknessii cotton showed that:（1）sterile cytoplasm had no significant adverse effect on cotton seedling growth,and there was an increasing trend in plant height,fresh weight and dry weight in SH compared to NH and SR compared to NR,but the difference was not significant;（2）the net photosynthetic rate of sterile cytoplasm heterozygous recovery line SH and sterile cytoplasm recovery line SR was significantly higher than that of sterile cytoplasm heterozygous recovery line NH and sterile cytoplasm recovery line NR at the seedling stage.The net photosynthetic rate was significantly higher in the seedling stage than in the fertile cytoplasmic recovery line NH and the fertile cytoplasmic recovery line NR,with the opposite trend occurring after the boll stage.The trends of transpiration rate,stomatal conductance,intercellular CO₂ concentration and net photosynthetic rate were basically the same;（3）both the sterile cytoplasmic heterozygous recovery line SH and the sterile cytoplasmic recovery line SR had significantly lower anther fertility than the fertile cytoplasmic heterozygous recovery line NH and the fertile cytoplasmic recovery line NR under high temperature stress,mainly in the form of significantly reduced pollen volume,fertile pollen rate and in vitro pollen germination rate;（4）the sterile cytoplasm had a significant negative effect on yield traits,mainly in the form of significantly lower seed cotton yield and lint cotton yield,and significantly lower boll yield per plant and Lint percentage;（5）sterile cytoplasm had no significant effect on cotton fibre quality,and increased cotton fibre strength at the Anyang site,but the difference was not significant;（6）overall,the negative effects of sterile cytoplasm on traits such as net photosynthetic rate,anther development and yield were more pronounced in the Yangtze River basin cotton region where summer temperatures were higher.The results of the restorer gene effect showed that:（1）the restorer gene had no significant effect on cotton seedling growth traits,anther development and net photosynthetic rate during the whole reproductive period;（2）the restorer gene had a significant positive effect on cotton yield traits in the Yellow River Basin cotton area,but no significant effect on cotton yield in the Yangtze River Basin;（3）the restorer gene could significantly increase cotton fibre length.