Studies On Genetic Mechanism Of Cytoplasmic Male Sterile Pepper And The Molecular Markers Related To The CMS Gene

Pepper (Capsicum annuum L.) is world-wide vegetable with great importance to flavouring industry. Pepper is the second largest vegetable crop in China. The cytoplasmic male-sterility (CMS) of pepper is the important way of utilization of heterosis. Using CMS pepper to produce hybrids is one of the major objectives in the present world pepper breeding. In addition, the CMS pepper is the best experimental material for the inheritance of character, cytology and molecular.Researches on CMS pepper have an important value for enrichment of CMS mechanism. Based on different CMS lines, maintainer lines and restoring lines in pepper, F1, F2, F1 XB, F1 XF1 and AX(R1 XR2) population were constructed and the inheritance of CMS trait was studied; The abortive mechanism of CMS pepper was investigated by observing the meiotic behavior and male gametes development under optical and transmission electron microscope. RAPD and AFLP techniques were used to analyze the genomic DNA and mitochondria DNA patters to obtain the polymorphic bands that related to the CMS trait for further studies. The results are as bellows:1. CMS 21 A, YanA and 8A belonged to sporophytically cytoplasmic male sterility, and possessed the same genetic trait. The sterility of CMS 21 A, YanA and 8 A depended upon the sterile cytoplasm and one pair recessive gene. The genetic effects of cytoplasmic sterile gene in pepper expressed mainly on the parthenocarpy, and there was the significant difference of parthenocarpied fruitsetting ratio between CMS YanA, 8 A and CMS 21 A. The cytoplasmic male sterile gene had no significant effects on main agronomic traits, such as plant size, fruitsetting number, fruit size and yield. The major agronomic traits in F1 progency made by CMS lines were slightly better than these emasculated by its maintainer lines. It means that sterile cytoplasmic gene possessed of the advanced function and positive effects. The results of propagating experiment showed that sterile cytoplasmic gene had not negative effects. It's more efficient to propagate and maintain CMS lines and produce hybrid seeds by artificialsupplementary pollination in plastic greenhouse than in open field. Completely fully restoring lines, Xiong 804, LS₇, Xiangzi, Luozi, SI201, sweet and hot pepper inbred translated by R-gene and the partial restoration of Nanchang 92-1 and Luotian No.2 to CMS 21A and 8A were definited. The completely restoring lines possessed a pair of dominate restoring genes. The restoring genes between Xiangzi, Luozi and hot pepper inbred translated by R-gene was allele, and was not allele with the restoring gene of SI201. The restoring genes were mainly distributed in the hot pepper inbreds, there were less restoring genes in sweet pepper than in hot pepper.2. Meiosis in CMS pepper was normal, and uni-nucleate pollen grains could be released from the tetrads of CMS inbred line and the fertile maintainer line. At metaphase I, the chromosome constitution was composed of nine ring bivalents and three rod bivalents. Equal chromosome divisions resulted in two poles with chromosome n = 12 at anaphase I, and four poles at anaphase II. After tetrad stage, however, only the uni-nucleate pollen grains from the fertile maintainer line could develop into functional gametes, while the uni-nucleate pollen grains from the CMS lines went through a process of rupture and the cellular components were released into the anther sac. Observations of paraffin sections viewed with the light microscope showed that the tapetum of CMS inbred line 8A at uni-nucleate stage swelled abnormally and pressed against pollen grains of the locule. Further observations with transmission electron microscopy revealed that the mitochondria in 8A tapetum were highly vacuolated, and there was no accumulation of sporopollenin on the surface of CMS 8 A pollen grains, suggesting a close relationship between early degeneration of tapetum, gross morphological changes in mitochondria and the CMS.3. 213 out of 380 primers gave the amplified products on the genomic DNA between CMS line and its mainta...