Genetic Studies On DGMS Line Shaan-GMS And Ogu-nwsuaf CMS In Brassica Napus L,

Rapeseed which has significant heterosis is one of the most important oilcropsworldwide. The key step to utilize heterosis is to establish a simple and efficient pollinationcontrol system. Up to date, the main important systems in hybrid rapeseed production inChina are cytoplasmic male sterility (CMS), genetic male sterility (GMS), chemicalhybridizing agents (CHA) and self-incompatibility (SI). Because of the advantages of GMS,such as complete and stable sterility, almost no negative cytoplasmic effects, and easilytransferable characteristics to diverse genetic backgrounds, GMS systems have been usedwidely and have gradually become an effective system in hybrid rapeseed production inChina.So far, several kinds of GMS mutants have been discovered in B. napus. In1985, Li etal discovered and reported fertility of a new GMS mutant Yi-3A was controlled by anepistatic interaction of the dominant GMS gene (Ms) and the suppressor gene(Rf). Thisgenetic model provided a theoretical basis for the utilization of DGMS in hybrid rapeseedproduction. Recently, Song et al had found the fertility of Rs1046AB derived from Yi-3Aand609AB bred by themself more comformed with genetic model of one gene with multiplealleles. Therefore, this study was carried out from cytological, genetic and molecular level inorder to reveal the genetic model of DGMS line Shaan-GMS and clarify whether the fertilityof this mutant was conditioned by an epistatic interaction of the dominant GMS gene (Ms)and the suppressor gene (Rf) or by one gene with multiple alleles at the same time. Theresults obtained are as follows:1) According to morphological observation, squanshing and sliced observation, cellmorphology statistics, the result indicated that the pollen mother cells (PMCs) of DGMSline0A30A derived from Shaan-GMS were degenerating at the beginning of meiosis andcould not pass the anaphaseⅠstage, with no dyads or tetrads formed, suggesting the DNAdamage checkpoint and spindle assembly checkpoint were activated in sterile anthers.During meiosis process of the sterile plants, several kinds of abnormal meiotic cells couldbe observed: nuclei condensed PMCs, cells with micronuclei, collapsed cells,plasmolysis-cell, cells connected with nucleoplasmic bridge, and "microspore'sanalogue" developed from PMCs without meiosis but enclosed by the exine wall. Local damaged cells of tapetum in sterile anther were discovered about at metaphaseⅠstage,then degraded gradually and collapsed finally.2) In order to reveal the genetic model of DGMS Shaan-GMS fertility in B.napus, two typesof crossing were made between sterile plants of homozygous GMS two-type line with therestorer lines, and between fertile plants of homozygous GMS two-type line with fertileplants of heterozygous two-type line, respectively, then fertile plants of the resulting F1were testcrossed with fertile plants of heterozygous two-type, the fertile plants in thisprogeny was selected to self and the male sterile plants to backcross with fertile plants ofheterozygous two-type. In florescence, fertility of all above progenies was investigatedand Chi-square test was conducted. The preliminary results suggested that the restoregene of new restore lines9A49,9C390may be allelic to male sterile gene of Shaan-GMS.Restore gene in fertile plants of homozygous Shaan-GMS two-type line was allelic tomale sterile in fertile plants of heterozygous Shaan-GMS two-type line.3) Five randomly selected fertile and sterile individuals of homozygous GMS two-typelines, heterozygous GMS two type lines were pooled to construct two fertile bulks andtwo sterile bulks. These four DNA bulks were used to screen SRAP, AFLP primers andfive fertile and sterile DNA samples to screen SCAR primers. The results showed thatonly one pair of SCAR primer could amplify polymorphic band between the fertileindividuals and sterile individuals of heterozygous GMS two-type line, which meaningthis band was specific to the gene Ms. We had also screened out14SRAP primers to Mfloci,7primers to ms loci. From210AFLP primer combinations, we selected31primercombinations which could amplify characteristic bands of Mf, and4primer combinationswhich could amplify characteristic bands of ms.4) The restoring and maintaining relationship between the Ogu-NWSUAF CMS and OguCMS was different. A multiplex PCR assay showed that Ogu-NWSUAF CMS couldamplify the characteristic fragments both of Ogu CMS system specific gene-orf138product and Nap CMS system specific gene-orf222product,which showed that themolecular characteristics of Ogu-NWSUAF CMS was different from that of Ogu CMS.The restoration of Ogu-NWSUAF CMS was controlled by a pair of dominant nucleargene.