Genetic Investigation Andcytological Comparison Of Twogenic Male Sterile Lines In Brassica Napus L.

Genic male sterility(GMS)is one of effective pollination control systems in hybrid rapeseed(Brassica napus L.)breeding.The recessive GMS line 9012 A and the male sterility lembke(MSL)have made a great contribution to the utilization of heterosis in rapeseed.Male sterile line 5A122,whichderived from the hybrid C022 which was developed on the basis of the recessive GMS line 9012 A.Male sterile line5A135 was derived from the hybrid Marthow which was developed on the basis of MSL male sterility.To reveal anther abortion period and characters as well as genetic relationship of 9012 A and MSL,cytological observations and genetic research were employed to compare the similarities and differences between the two lines.The cytoplasm type of two male sterile lines was identified by one-step multiplex PCR.The obtained results will lay a solid foundation for rapeseed hybrid breeding.The main results are as following:1.Cytological results showed that the 9012 A had been abnormal at the pollen mother cell stage,such as tapetum shedding,dissolved,inflated,and pollen mother cells malformed,dissolved.Some of anthers could develop to microspore stage.Deformed microspores colored lightly were tightly adhered together and had exine at uninucleate pollen stage.Subsequently,the tapetum and microspores dissolved together.At last,only the exine adhered together leaving in the anther sac.The MSL had been abnormal at the pollen mother cell stage,such as tapetum shedding,dissolved,inflated and not complete,and pollen mother cells dissolved.Some of anthers could develop to tetrad stage.The tapetum extended radially and contained a particularly large vacuole.Some tetrads had concentrated and stained deeply with vacuolization.The normal tetrads were rare and very few microspores released from the tetrad.Finally the vacuolized,elongated tapetum and the concentrated tetrads dissolved together,the anther sac atrophied.2.MSL and 9012 A had the same temporary maintainer line,while MSL had different maintaining and restoring relationship with Pol CMS,Double recessive male sterile line and Shaan-GMS.3.The multiplex PCR analysis was used to identify cytoplasm type of 5A122(9012A)and 5A135(MSL).It appeared that the given cytoplasm type(Ogu,IP-Ogu,Shaan 2A,Pol A,Nap,Cam)was associated with a specific combination of the respective PCR products.5A122(9012A)could amplify the combination of 1102-bp and 465-bp,which was specific to Nap type cytoplasm.5A135(MSL)could amplifya500-bp band,which was specific to cam cytoplasm.4.The male sterile lines derived of MSL were crossed with different inbred lines and the resulted hybrids were analyzedfor the main agronomic traits.The results showed that there were significant differences for all traits except for the effective number of branches and the main branchlength.Among them,the plant height of hybrids 5A138,5A161,5A162 were greater than other combinations,the setting position of branch of 5A161 was the highest.The siliques per plant of 5A138 and 5A162 were much more than other combinations.The seed number per silique of 5A162 was greatly more than others.Meanwhile,1000-seed weight of all hybrids were lower than that of the control variety(Qinyou No.7).Seed yield per plant of 5A162 wasthe highest among all hybrids.In summary,MSL has breeding value in Chinese hybrid breeding.