Identification And Formation On Natural Hybrids Of The Campeiostachys Drob

Natural hybridization is considered to be an important way of speciation,providing raw materials for the evolution of biodiversity.However,in the perennial species of the Triticeae,natural hybridization between different genera or different species is common.Triticeae plants contain a large number of perennial forage resources,among which Campeiostachys is an allopolyploid species with the St,Y and H genomes.At the experimental site of the Sichuan Provincial Grassland Science Research Institute in Hongyuan County,Sichuan Province,there are many different genera and species of hardy and drought-tolerant Triticeae perennial grass.In the field where Campeiostachys breviaristata was planted,we found two plants which were suspicious natural hybrids.A variety of methods were used in this study,including morphology,meiotic pairing behavior,genomic in situ hybridization(GISH)and molecular phylogenetic analysis,to identify the genomic constitutions of the natural hybrids,to explore the parental species and the formation mechanism of this two natural hybrids.The experimental results are as follows:1.Observed by morphology,these natural hybrids are perennial grasses,stronger than the surrounding plants,and similar in appearance to Campeiostachys breviaristata,e.g.spikelet 2 per node,lanceolate glumes,with short awns and the awn length is 4 ～ 6 mm.2.The pollen fertility of these two natural hybrids were 21.2% and 13.3%,respectively,while the seed setting rates were 18.6% and 10.7%,which were lower than normal plants.The fertility of two C.breviaristata(ZY17007,ZY17009)were 88.7% and 86.8%,and the seed setting rate were 82.5% and 84.3%.3.The number of chromosomes in metaphase mitotic indicates that these hybrids were hexaploids with 42 chromosomes(2n= 6x= 42).4.Meiotic pairing was observed in the two natural hybrids.Chromosome pairing of the two hexaploid hybrids was complete,with averaged 20.44 and 20.93 bivalents per cell,respectively,and the C-values were 0.92 and 0.94.The results indicated that the genome of these two hybrids have high homology.5.The results of two-color(St-green,H-red)genomic in situ hybridization(GISH)showed that the genomic constitutions of the two natural hybrids was St St HHYY;6.The phylogenetic analysis based on the DMC1 sequence showed that the possible parents of the two natural hybrids were C.breviaristata,Elymus submuticus,and Elymus atratus.The phylogenetic analysis of the chloroplast gene rps16 showed that female parent of the two natural hybrids was C.breviaristata.Combined with morphological and molecular data,the parents of the two natural hybrids were C.breviaristata and E.submuticus,and C.breviaristata was the female parent.