Chromosome Mapping Of Branched Spike Gene And Gene Cloning Of Ramosa2 In Wheat

Wheat is one of the most important crops in the world. The core of wheat improvement intensively depends on the revealation of genetics and molecular mechanism of important agricultural characteristics. In history, each breakthrough in the breeds owed to the creation,discovery and the use of new genetic resource. "FEN 33", one of the wheat inflorescence morphology mutants, has many branched spikes growing upon the main spike node. Therefore,"FEN 33" may effectively increase yield due to the more spikes. Our research on "FEN 33" aimed to illuminate the molecular mechanism of wheat inflorescence development and fully explore its potential application value in the yield. In this study, we systematically analyzied histologic morphology and inheritance law of "FEN 33" and maped the branched spike gene by SSR markers. Wheat homological gene ramosa2 was cloned, which arised branched inflorescence in maize.In FEN33, there were 11 branched spikes and 118 seeds growing on each main spike on average. A large F2 population of "CS" crossed with "FEN33" was constructed, containing 40,000 F2 individuals. Basing on the separate proportion of branched spike in this population, our study found that the branched spike was mainly determined by two recessive genes and simultaneously influenced by some other genes.209 SSR markers were selected for scanning the whole wheat genome, and 87 of them have polymorphism in the two parents. Polymorphism markers and Bulked Segregant Analysis (BSA) were applied in the analysis of 96 individuals with branched-spike in F2 population. The result was that branched spike gene was respectively linked to SSR markers on 2A chromosome and 2D chromosome, so branched spike gene was elementarily located to the two chromosomes in wheat. On the 2A chromosome, location of branch spike gene was near SSR markers gwm372,wmc502, and the genetic distance was 9cM and 11.25 cM respectively. On the 2D chromosome, the gene was located near SSR markers gwm484,gwm102, the genetic distance was 15 cM and 17 cM respectively.Erik Vollbrecht(2005),Esteban Bortiri(2006),Namiko Satoh-Nagasawa(2006) ect cloned gene ramosa1,ramosa2,ramosa3 which controlled the inflorescence branch in maize and any mutation in the three genes could increase the inflorescence branchs. In this study, wheat homological gene ramosa2 was firstly cloned according to the sequence reported on barley,maize,sorghum and rice. Many ramosa2 homologic sequences were detected in "FEN33" and "CS", which indicated that ramosa2 may have more than one copy in Triticum aestivum L. The amino acid sequence deduced from the nucletide sequence has the respective similarity of 95% with barley,81.8% with rice,79.9% with maize and 79.2% with sorghum. However, the relationship between the branched spike gene and ramosa2 need to be further studied in the future.In conclusion, according to the special wheat branched spike phenomeno, our research focused to study the mechanism of branched spike, which set up good foundation for cloning of branched spike gene and illumination of the mechanism of branch spike, and help to finally apply "FEN33" to the wheat high yield breeding.