SSR Marker Location On The Restorer Gene For M-Cytoplasmic Male Sterility In Soybean

As an efficient approach for crop yield improvement.the use of hybrid varietiesh as been a widely used approach invarious commercial food crops around the world.Great success has been achieved in the development of hybrid varieties in several major crops,including rice and maize.Due to lack of genetic male sterile resources or mutants.soybean is one of a few crop species,in which heterosis has not been exploited to an extent that is practically viable until recently.Recently successe in the development of soybean cytoplasmic genetic male sterile(CMS) lines and their application on the use of heterosis in the crop was achieved in China,which markecd the leading position of China in the field in the world.Soybean CMS lines can be classified into two types according to their origins.M typeis derived from ZD8319.Although these lines has been used for breeding of hybrid varieties,limited information is available on their mode of inheritance,the genetic markers associated with restorer genes.In this study,M type CMS lines and this corresponding W931A restore lines was used to conduct a series of crosses.By studying the segregations pattern of the fertilities of F₁,F₂ the in heritance of the M type CMS lines was identified.DNA was extracted from the F₂ Segregat -ing population and screened with simple sequence repeat(SSR) markers to look for genetic Markers closely linked to the restore gene.The results of the study are summarized as followed.1.Pollen abortion is an indicator for identifying the male sterile plants.Pollen fertility of F₁ plants from crosses.The F₁ pollen is semi-sterile,which provided evidence that the traits ofmale sterility in these lines are controlled by a single-genie gametophytic type system.Investigation of the fertilities of this F₂ plants.The result provides additional evidence that the male sterility in M types CMS lines is controlled by a single genic gametophytic-type system.2.Analysis on the fertilities of individual CMS plants with different extend of male sterility suggested that soybean male sterility can be affected by environmental variables.In different environmental conditions,the male sterility and fertility can be alternated.This alternation can be due to quantitative changes in which the percentage of pollen abortion varies indiff erent growth years.It can also be due to qualitative change,in which the sterile cytoplasm can be converted into fertile cytoplasm.This type of alternating resulted in the occurrence of unexpected male fertile plants in the progenies of the sterile lines.The converting rates vary in diferent genotypes.3.It is confirmed that restoration of the fertility of the M type of soybean CMS lineis control -led by a single dominant nuclear gene.Three SSR makers,Satt684,Satt276 and Satt545, which are genetically linked to the uclear restorer gene,were selected by screening of 213 pairs of the SSR marker.The genetic distance between markers and the restorer genes are 29.5cM,10.7 cM and 14.1 cM respectively.The nuclear restorer gene is located in A1 linkage group according to(Song et al,2004) soybean genetic map.