Abstract:Brassica napus cytoplasmic male sterility (CMS) NRO4270A was obtained in the progenies of distant hybridization of Raphanus brassica (RRCC) and B.napus (AACC).(1)The fertility investigations of five consecutive years in both winter and spring rapeseed production areas showed that NRO4270A could not produce pollens completely and its male sterility was extremely stable,which could not be affected by environmental conditions,such as temperature and photo period.Its sterility rate and sterility degree are both 100%.(2)NRO4270A,pol,ogu,kos,hau CMS lines were test-crossing with the restorer lines of pol,ogu as well as cultivar Huashuang 4.It was suggested that NRO4270A had different restorer and maintainer relationship with pol,ogu and kos.(3)Microscopic structure analysis and comparison of anther developments of NRO4270A and its maintainer line NRO4270B indicated that NRO4270A pollen abortions occurred between the tetrad stage and the mononucleate stage.At mononucleate stage,its microspore exine could not form,and its tapetum was vacuolated and expanded.Eventually,its tapetum and microspore were completely degraded.The pollen sacs became empty and the pollens could not be produced in it.(4)The mitochondrial DNAs of NRO4270A,pol,ogu,kos,hau,NRO4270B and Huashuang 5 were analyzed through RFLP by 18 probe/enzyme combinations (six mitochondrial gene,atp1,atp6,atp9,orf222,cox2 and cob,as well as three restriction enzymes,EcoRⅠ,BamHⅠ and HindⅢ),respectively.In 11 combinations,NRO4270A showed significantly different bands with the other materials,suggesting that NRO4270A was a new CMS type.Its discovery and utilization will overcome the problems of environmental sensitivity of Chinese major CMS system and the singleness of sterile cytoplasm type in rapeseed hybrid seed production.