Breeding Of CMS Lines In Sweet Pepper(Capsicum Annuum Var. Grossum), Identification Of Molecular Markers And Biochemical Characters Of Abortion Linked To CMS

Capsicum annuum L.,an annual or perennial plant in capsicum genera of solanaceae originated from middle-south America.Up to now,pepper has become the second largest vegetable crop,planted about 1.35 million hectare area under cultivation in China.Pepper's heterosis is very obvious while the production of hybrid F₁ seeds is mainly propagated by man-emasculation in bud stage.But cytoplasmic male-sterility(CMS) of pepper is the most important way of utilization of heterosis.Using CMS pepper to produce hybrids can greatly decrease working procedures and costs,and guarantee hybrid seeds purity,and prevent parents to be stolen.So,using CMS pepper to select hybrids is one of the most intense popular in the present world pepper breeding.Studies mainly focus on the inheritance of male-sterile characters,creation and application of restorer lines,pollen abortive mechanism and molecular markers linked to CMS.Results were as follows:In the first part,it introduced the breeding of CMST6A and CMSMCA.Sweet pepper CMST6A and its maintainer line T6B,CMSMCA and its maintainer line MCB were successfully bred by hot pepper CMS21A crossed sweet pepper T6 or MC and backcrossed more than six generations.Heredity analyses showed that sterility of CMST6A was controlled by a pair of recessive genes.The observation with I₂-KI showed that sterile pollen percentage of CMST6A and CMSMCA were 98.4%and 97.8%respectively.In the second part,it studied the distribution of restorer genes of sweet pepper CMST6A.Identifying BC₁ fertility indicated that pepper cultivars can be divided into three groups:maintainers,restorers and segregations.CMS fertile restorer genes can be mainly found in long hot cultivars,while CMS maintainer genes easily found in sweet cultivars. Restorer genes of nine cultivars,84-1,Xiong ao 804,Xiangzi 13,Fu_M,Linear hot pepper, NT2M,horn.1,5-2R₁ and 5-2R₃,were located in the same gene site.In the third part,creation and heterosis application of CMS restorer lines in sweet pepper were studied.Sweet pepper restorer lines 5-2R₁,5-2R₂ and 5-2R₃ were developed by northem flat lantern sweet pepper,alfalfa garden early-maturing hot pepper in Nanjing and high lantern sweet pepper 5-2 by means of cross,backcross,self-pollination and testcross.CMS sweet pepper variety Jiangshu No.5 is bred by CMS8A crossed restorer line 5-2R₁,and other four new combinations were selected,Such as "CMS21A×5-2R₁", "CMSYinzaoA×5-2R₁","CMST6A×Xiong ao 804" and "CMSMCA×Xiong ao 804".In the fourth part,the RAPD analysis was conducted on 42 pepper inbred lines from China and overseas.Twenty-three primers selected from 340 random primers were used for 42 pepper samples.A total of 133 DNA bands were amplified,among which 111 were polymorphic.These 133 bands were analyzed using the UPGMA cluster software.The results showed that these inbred lines could be classified into 3 groups when the genetic distance was 0.124.Fertility restorer hot peppers were distributed in the groupâ… ,groupâ…¡and groupâ…¢.It was observated that the restorer genes were random in these tested hot peppers in the molecular level.In the fifth part,RAPD and ISSR analysis were conducted on the genomic DNA of CMST6A and its maintainer T6B in sweet pepper.The specific fragment RAPDAO19₁₄₀₀ and ISSR-8₈₄₀ in CMS line were found.Sequencing analysis of AO19₁₄₀₀ indicated that the length of the sequence was 1378 bp.According to the DNA sequence,one pair of primers was designed and the RAPD markers were transformed into SCAR marker SCAO19₄₉₈. Sequencing analysis of ISSR-8 showed that the length of the sequence was 840bp,with 52%identities and 67%positives of its amino acid sequence with clone LE_HBa-20F17 on chromosome 4 from S.lycopersicum.In the last part,it studied biochemical characters in sweet pepper CMS Lines and its maintainer lines.Compared with maintainer lines,the contents of free proline and free lysine in sterile lines CMSZTA,CMS17A and CMS8A were obviously lower than maintainer lines ZTB,17B and 8B.Free threonine and arginine contents in sterile lines were obviously higher than maintainer lines.Total content of free amino acids in anther in sterile lines was significantly lower than maintainer lines.The content of soluble sugar and protein and the activity of CAT were low in both leaves and buds while the activities of SOD and POD were higher in CMS line than maintainer line.These results suggest that the variation of free amino acids,soluble sugar,protein content and enzyme activities were related to pollen abortion in CMS.