Polyploidization And Comparative Research On Intergenomic Hybrids(ACD,AACD)of Oryza

Heterosis,a common heredity phenomenon in nature,is used as an important way to improve yield and quality and increase resistance to stress by breeders.Many hybrid crops,taking hybrid rice for example,show better character than their parents such as higher plant,bigger seeds and more yield due to heterosis.However,heterosis utilization in rice faces the bottle neck obstacle when rice yield goes up to 1000 kilogram per 667 square meter,in that less elite genes in hybrids and less diversity between parents exist.The excellent genes were widely utilized in cultivate rice Oryza sativa but few genes in wild rice were introduced to 0.sativa.but these useful genes and diversity in over 20 species of Oryza are valuable resource to rice breeding,which will benefit to solve the problem of yield increasing less than 5%currently.In order to make full use of wild rice,a novel rice breeding strategy was developed by Detai Cai with setting up super rice variety through intergenomic hybridization and polyploidizaton.His research group created triploid by crossing 0.sativa(AA)with 0.alta(CCDD),rescued the immature embryos,and doubled the whole chromosomes of triploid to form allo-hexapolyploid rice(AACCDD),which displayed male sterile and made it difficult to explore the useful genes in C and D genome.On the basis of allo-hexapolyploid rice(AACCDD),the 48 chomosomes,stable and high liked as cultivated tetraploid rice(AACD)were generated by crossing allo-hexapolyploid rice(AACCDD)with diploid rice variety HN2026(ApAp)possessing Polyploid Meiosis Stable gene(PMeS).This study continues to double the chromosomes of tetraploid rice(AACD)to generate autoallo-octopolyploid rice(AAAACCDD),and confirm the polyploidization at the level of morphology,cytology and DNA.The results show as following:1.Triploid hybrid(ACD),autoallo-tetraploid(AACD)and autoallo-hetraploid(AACCDD)plants showed different morphology compared as cultivated rice parents,stronger stem,more flourishing growth,more tillers,longer and wider flag leaves,and some morphologic character was similar to the wild rice parent 0.alta(CCDD).But the autoallo-octoploid rice(AAAACCDD)plants show slow growth,short and small stems,less tillers,and abnormal growth.2.The chromosome number counting showed the number of Cw026-3x(ACD)was 36,Cw026-6x(AACCDD)was 72,Cw-4x(AACD)was 48,and Cw-8x(AAAACCDD)was 96,which confirmed Cw-8x was real autoallo-octoploid in cytology.3.Pollen mother cells of different hybrids development process compared with that of the parents show abnormal behavior:most of the polyploidy cells in triploid(ACD)and hexaploid(AACCDD)developed to meiotic prophase ?,few cells could developed to the meiotic metaphase I;cells in tetraploid(AACD)developed abnormally,displaying univalent,trivalent,quadrivalent and multivalent in meiotic prophase ?,and lagging chromosomes in anaphase ?,metaphase ? and anaphase ?.4.The real hybridity of triploid(ACD),tetraploid(AACD),hexaploid(AACCDD)and octoploid(AAAACCDD)was confirmed by DNA markers RM598 and RM3513,which contained the amplified bands with PCR from both A genome and CD Genome.These results are the first report and which will be a very good background of The triploid,tetraploid,hexaploid and octoploid rice materials are vital to genomic evolution research in Oryza and provide important germplasm to rice polyploidization breeding.