Studies On NCa,A Cytoplasmic Male Sterile In Brassica Napus L.

Oilseed rape is one of the most important oil crops that cultivated extensively in the world. Cytoplasmic male sterility (CMS) is the most valuable pollination controlling system for hybrid production. In China, about 70% of the rapeseed hybrids contain the Polima cytoplasm which lead to the cytoplasmic monotone. So exploitation of cytoplasmic diversity has become the key goal for rapeseed breeders. NCa CMS was obtained from the backcrossing descendents of hybridization between Brassica napus L. and Brassica carinata and had showed great economic interest for breeding program in the previous researches. We determined the restorer-maintainer relationship of NCa, pol, nap and ogura CMS by comparing the fertility of F₁ which obtained from these four CMS lines pollinated by 104 accessions of different originals. The pollen abortion stage and ultra-structure characteristics of NCa CMS were observed through light microscopy and transmission electronic microscopy (TEM). And the mitochondrial (mt) polymorphisms of NCa, pol, nap, ogura and tour CMS were discovered by RFLP analysis. We revealed the transcription profile of NCa CMS under the control of restorer gene, and also compared the differential expression of 10 mt genes in different organs in NCa CMS, maintainer line and fertile F₁. At last, differentially expressed genes during pollen abortion in NCa system were cloned by means of cDNA-AFLP. All of these researches on NCa system would be informative and valuable for its application into breeding program. The major results are presented below:(1) The restorer-maintainer relationship determination revealed that NCa CMS showed different fertility from nap, pol, ogura CMS when crossed to the 104 accessions of different originals. NCa maybe a CMS type different from nap, pol, ogura CMS.(2) The anatomical observations on the anther development of NCa CMS by light microscopy and transmission electronic microscopy showed that the anther abortion occurred at the later mono-nucleus microspore (MNM) stage. The microspore mother cell of NCa could pass through meiosis and form tetrads and then tetrads could release microspores, which were similar to the fertile line. The released microspores with one nucleus could continuously develop and form pollen wall soon later. The protoplast and nucleus of MNM degraded in succession and just left the empty pollen wall or with large vacuoles after abortion. The tapetum development was similar to that of the fertile anther up to tetrad stage but after that the protoplasts of tapetal cells were rich in small vacuoles and degenerated gradually. Anther development of NCa sterile line was obviously different from all of the other kinds of male sterile lines examined before, because its abortion stage revealed here was later than any of the examined sterile types and it formed pollen wall soon after microspores released and remained that until pollen degradation.(3) 42 out of the total 54 combinations of probe/enzyme used in RFLP analysis could discover the different bands among NCa, pol, nap, ogura and tour CMS. 5 combinations of atp1/EcoR I, atp1/Hind â…¢, atp6/EcoR I, atp8/BamR I, orf139/BamH I, could powerfully distinguish the 5 CMS lines from each...