Breeding Of A New Alfalfa Variety With Multifoliate Traits By Space Mutation

Space mutation breeding is a highly innovative breeding method,which is widely applied to many aspects of crops in China.However,the space mutation breeding of forage grasses is in the initial developing phase.As an important perennial legume forage in China,the research of alfalfa(Medicago sativa L.)multifoliate traits plays an important role in alfalfa breeding.By space mutation of“Shen zhou No.3”,four varieties of alfalfa were used as the materials in this study.Through beneficial mutants screening,the new multifoliate alfalfa germplasm were selected,and the new germplasm were evaluated in different regions,also transcriptome by RNA-seq between multifoliate traits and trifoliate traits were analyzed,respectively.The results were as follows:1.Four different alfalfa varieties were used to space mutation,341 mutants population were obtained after planting.Through 3 years consecutive observation of agronomic characteristics,44candidate materials with 8 different variation profiles were selected,accompanied with the mutation rate of 12.9%.Notably,6 different alfalfa cultivars with multifoliate traits were importantly selected,and the mutation rate was 1.76%.2.A new alfalfa germplasm named HM-2 was selected using individual selection and mixed selection.HM-2 was well adapted to different climatic conditions of different regions,such as Lanzhou,Longxi,and Qingyang.The average multifoliate rate of HM-2 was 69.75%,also 79.26%and 1005.39%higher than Hangmu No.1(38.91%)at P<0.01 and other multifoliate alfalfa cultivars(6.31%)at P<0.01,respectively.There was no significant difference among different climate conditions of HM-2,and the multifoliate traits of HM-2 possessed good hereditary stability.3.Under the same condition,the hay yield of HM-2 was reached to 19784.2 kg/hm~2,which was 7.99%higher than Hangmu No.1,17.44%higher than Sandeli,and 33.81%higher than the multifoliate alfalfa cultivar from abroad.4.The nutrient contents of HM-2 was evidently improved than the control,the content of CP was reached to 21.8%,which was 11.22%higher than Sandeli(19.6%),2.83%higher than Hangmu No.1(21.20%),6.97%higher than other multifoliate alfalfa cultivars(20.38%).Moreover,the protein content per unit area was 5220.91 kg/hm~2,and was 36.88%higher than the control.The relative feeding value was 142.1%,and was 25.43%higher than the control(P<0.05).5.RNA-seq was investigated between the leaves of HM-2 and the control alfalfa cultivar,38.89 Gb clean data was obtained,and 95259 unigenes were assembled.239 differentially expressed genes(DEGs)were selected,with 146 genes up-regulation and 93 genes down-regulation.Furthermore,28 genes were only expressed in HM-2 leaves.In total,170 DEGs ware annotated.6.The new germplasm HM-2 has passed the systematic research and has been reviewed by the National Grass Variety Approval Committee for participating in the national grass variety regional trial.