Sterility Characteristics And Genetic Mapping Of Cytoplasmic Male Sterile Mutant CMS102 In Capsicum Annuum L.

Pepper（Capsicum annuum L.）,which originated in tropical South America,is an annual or limited perennial herb,and is an important vegetable crop.Pepper has strong hybrid advantage,but there are still some problems in pepper hybrid seed production,such as complex seed production procedure,high cost and low seed purity.Three-line hybrid breeding based on the principle of cytoplasmic male sterility can not only solve the problems existing in pepper hybrid breeding,but also speed up the breeding process of improved variety improvement and new variety selection.Therefore,it is of great significance to study the abortion mechanism of cytoplasmic male sterility and the location and cloning of fertility restorer gene in pepper.In this study,using pepper cytoplasmic male sterile mutant CMS102 and its corresponding restorer line ST-8 as materials,the anther cytological morphology of flower buds at different developmental stages was observed by paraffin sections,and the important physiologically active substances of flower buds at different developmental stages were determined,and the abortion characteristics of CMS102 were analyzed.The genetic analysis of CMS102was carried out by constructing F₂ genetic segregation population,and the restorer gene（Ca Rf102）of male sterile mutant CMS102 was finely mapped by BSA analysis.At the same time,the flower buds of the two materials at tetrad stage were analyzed by transcriptome technology,and the differentially expressed genes and their functions during the critical period of pollen abortion were compared.The main results are as follows:（1）The microstructure of anther tissue at different developmental stages was observed:the development of the anther tissue of CMS102 and ST-8 was obviously abnormal at the tetrad stage.In the CMS102 anther tissue,the tapetum cells were abnormally dilated and highly vacuolized,and the extruded tetrad was extruded.While in the ST-8 anther tissue,the tapetum developed normally,and the tetrad formed after pollen mother cell meiosis began to separate with the degradation of callose.In the uninucleate microspore stage,the squeezed tetrad and overexpanded tapetum in CMS102 anther tissue died one after another to form an obvious dead cell band,while in this period,the tetrad isolated from ST-8 anther tissue developed into uninucleate microspores and then continued to develop into mature pollen grains,and the tapetum degenerated completely at binucleate microspore stage.（2）Comparison of physiologically active substances in different developmental stages of flower buds showed:the content of soluble sugar in flower buds of CMS102was higher than that of restorer line ST-8.The content of soluble sugar in CMS102bud is higher than that in restorer line ST-8.The content of soluble protein in ST-8 bud was slightly higher than that in CMS102,and there was significant difference in tetrad stage,which was 1.12 times higher than that in CMS102.The content of free proline in CMS102 was higher than that in ST-8 in the early stage of flower bud development,but in the later stage of development,free proline accumulated rapidly in ST-8,which was 1.60 times higher than that in CMS102.The content of MDA and the activity of POD in CMS102 were higher than those in ST-8 at all stages of flower bud development,and the maximum differences were 1.56 and 1.52 times respectively.（3）Genetic analysis showed that the fertility restoration of CMS102 was regulated by a single dominant gene.The genetic linkage map was constructed by using BSA and SNP genotyping technology.The Ca Rf102 locus of CMS102 was located in the 910.6kb region at the end of chromosome 6,that is,between PARMS markers PM7 and PM11.Combined with the results of transcriptome analysis,it is inferred that Ca6g27063,which encodes PPR protein,is a candidate gene for Ca Rf102.（4）A total of 2065 differentially expressed genes were identified by transcriptome analysis of ST-8 and CMS102 tetrads.GO enrichment analysis showed that these DEGs were associated with biological processes such as material transport,material and energy metabolism,hormone synthesis and metabolism and ROS metabolism.Compared with ST-8,the POD enzyme gene affecting ROS metabolism was significantly down-regulated in CMS102,and cytokinin dehydrogenase（CKX）,which affecting cytokinin metabolism,was significantly up-regulated in CMS102.