Breeding And Utilization Of Cytoplasmic Male Sterile Lines In G.hirsutum

Cotton is one of the most important economic crops in the world.The main objective of breeding is to increase the yield of cotton.The utilization of cotton heterosis is one of the most important ways to increase yield and improve the comprehensive character of cotton.Due to high labor cost,cytoplasmic male sterile three-line hybridization for seed production is imperative.In 1998,a new cytoplasmic male sterile germplasm line of upland cotton(G.hirsutum)was obtained,through a sterility mutant in the recombinant inbred line of upland cotton with southern propagation to boost up generations.In 2015,a new upland cotton restorer line "Zhehui-08" was developed.Three hybrid combinations were constructed in 2016,and the hybrid restoring rate reached to 100%,but the yield competitive advantage was not strong.This study intends to carry out backcrossing between the new upland cotton sterile line and ten parents with high combining ability to improve the combining ability of the sterile lines.Through constructing the three-line hybrid cotton combinations,the yield and fiber quality traits in Dangtou,Anhui province were investigated,and the main results are as follows:Through backcrossing,the cytoplasmic male sterility gene of upland cottons was transferred to ten parents of strong dominant hybrid cotton combinations.And ten new cytoplasmic male sterility lines were obtained successfully with 100% sterility rate.Ten newly transferred cytoplasmic male sterile of upland cotton were orderly,consistent,and the overall plant characters were similar to its maintainer.Through pollinating male sterile lines with maintainers,the boll-forming and boll-opening of male sterile lines were normal.The phenotypes of bolls and fibers were similar with maintainer.However,the lint yield,lint percent and seed germination traits of male sterile lines were lower than maintainers.Fiber strength and elongation were slightly lower than maintainers.And fibers were longer than maintainers.Through crossing ten cytoplasmic male sterile lines of upland cotton with restorer lines(Zhehui-08),the lint yield of 10 three-line hybrid cotton combinations was 114.77~152.4 kg/mu,with the average of 135.77 kg/mu.While it was 131.57 kg/mu in CK.The boll weights ranged from 5.37 g to 6.47 g,with an average of 6.0 g and 5.5 g as controls.The lint percent were 38.63~ 45.17%,with an average of 41.27%,compared with 41.4% for the CK.Fiber lengths ranged from 28.38 to 31.62 mm,with an average of 29.54 mm and a control of 29.36 mm.The fracture ratio strength was 29.67 to 32.42 cN/tex,with an average of 31.23 cN/tex,compared with 29.6 cN/tex for the CK.Macron values ranged from 4.2 to 1.73,averaging 4.53 versus 4.55.,The heterosis analysis results of 10 combinations of cytoplasmic male sterile lines of upland cotton showed that the mid-parent heterosis of lint yield of male sterile line combinations was 9.25-31.34%,with an average of 21.13%.The competitive advantage was 12.77% to 15.83%,with an average of 3.19%.The mid-parent heterosis in fiber length was 0.3% to 3.23%,with an average of 2.45%,and the competitive advantage was-3.34% to 7.7%,with an average of 0.62%.The fiber strength of mid-parent heterosis was 0.58% to 10.22%,with an average of 4.77%,and the competitive advantage was 0.24% to 9.53%,with an average of 5.51%.The cytoplasmic male sterile gene of upland cotton had no negative effect on the yield and fiber quality of three-line hybrid cotton.The yield of male sterile hybrid was higher than that of maintainer hybrid combination without cytoplasmic male sterile gene.And there was no significant difference in fiber quality and character.Two strong advantage combinations ZDH124A×Zhehui-08 and ZDY012A×Zhehui-08 were selected.The lint yields of these two combinations were 148.27kg/mu and 145.93kg/mu,respectively.Which increased by 16.7kg and 14.36 kg compared with the CK,respectively.Moreover,the fiber quality and characters were superior,which had a greater utilization value and application prospect.In this study ten upland cytoplasmic male sterile lines were developed,which could be affected and alleviate the high cost of artificial emasculation during hybrid seed production in production practice.And also provide parental materials for selection and research of cytoplasmic male sterile lines in upland cotton.