Study On The Growth Characteristics And Transcriptomics Of Backcross Population Of Multifoliate Alfalfa

Multifoliate Alfalfa(Medicago sativa L.)have the potential to improve the yield and quality.In this paper,the backcross population was constructed by using multifoliate alfalfa and trifoliate alfalfa as parents,and the growth characteristics and the variation of multifoliate character in growth stages of mulitifoliate alfalfa were studied.The correlation analysis of agronomic characters and yield of backcross population of alfalfa was carried out.At the same time,the morphological and structural characteristics and photosynthetic characteristics of different types of compound leaves of multifoliate alfalfa were studied.trifoliate and multifoliate compound leaves were selected to analyze the difference of transcriptome to screen the differentially functional genes.The purpose of this paper is to provide a basis for the study of mulitifoliate character and its controlling genes in alfalfa.It is helpful for the construction of genetic map of alfalfa and the screening of fine alfalfa varieties by molecular assisted breeding.The main results are as follows:(1)The plant height,growth rate,branch number,fresh/dry ratio,multifoliate rate and dry weight of backcross population(BC4m)with multifoliate alfalfa as reincarnation parent were better than those of backcross population(BC4t)with trifoliate alfalfa as reincarnation parent,which indicated that the agronomic characters and yield performance of backcross population with multifoliate alfalfa as reincarnation parent was better than that of backcross population with trifoliate alfalfa as reincarnation parent.The proportion of multifoliate plants in BCim population was 2.6 times higher than that in BC1t population.The plant height,growth rate,branch number,fresh/dry ratio and dry weight of mulitifoliate plants were better than those of trifoliate plants in the two backcross populations obtained by using multifoliate alfalfa and Trifoliate alfalfa as recurrent parents.The results showed that the agronomic characters of multifoliate alfalfa were better than those in non-multifoliate alfalfa.(2)There was highly significant positive correlation between plant height and dry weight(P<0.01),branch number and dry weight(P<0.01).There was a significant negative correlation between multifoliate rate and the ratio of stem to leaf,and there was a significant negative correlation between multifoliate rate with dry weight(P<0.05).The results showed that the increase of plant height and branch number of alfalfa could effectively increase the yield of alfalfa hay,and the increase of multifoliate rate of alfalfa could decrease the ratio of stem to leaf and increase the yield of alfalfa hay.The crude protein content of quinquefoliate alfalfa was higher than that of trifoliate alfalfa.The nutritional value of quinquefoliate alfalfa was higher than that of trifoliate alfalfa.(3)The occurrence of multifoliate compound leaves in Medicago sativa was very unstable.Some multifoliate alfalfa almost all showed the of characteristics multifoliate compound leaves,while some of the multifoliate alfalfa had only a small part of the compound leaves showing the characteristics of multifoliate compound leaves.The more abundant the leaf combination type was and the more the number of multifoliate compound leaves was,the more the leaf area of the main multifoliate compound leaves would be increased,while the leaf area of the trifoliate compound leaves would become smaller.The specific leaf area of multifoliate compound leaves was smaller than trifoliate compound leaves,and the specific leaf area of 7 lobule compound leaves was the smallest,which indicated that the characteristics of multifoliate compound leaves could improve the accumulation of photosynthesis products in alfalfa to some extent.The photosynthetic indexes of different types of compound leaves of multifoliate alfalfa were measured by photosynthetic instrument.The net photosynthetic rate and intracellular CO2 concentration of quinquefoliolate compound leaves of alfalfa were the highest,which indicated that the photosynthetic efficiency of quinquefoliolate compound leaves was the highest.(4)The transcriptome was sequenced to obtain 98,819 genes with an average length of 653.31 bp.The differentially expressed gene analysis showed that compared with the trifoliate control group,1067 differentially expressed genes were up-regulated and 1229 differentially expressed genes were down-regulated in the multifoliate group.The GO enrichment analysis showed that the number of differentially expressed genes was higher in catalytic activity,cell edge,plastid and chloroplast pathways.In the catalytic activity pathway,the number of differentially expressed genes was the largest,but the degree of enrichment was the smallest.In the biogenic pathway of plant morphological secondary cell wall,the enrichment degree of differentially expressed genes was the highest,but the number of differentially expressed genes was the least.The KEGG enrichment analysis showed that the number of differentially expressed genes was higher in amino acid biosynthesis,plant hormone signal transduction,starch and sucrose metabolism pathways,and the enrichment of differentially expressed genes was also significant.In amino acid biosynthesis pathway,the concentration of differentially expressed genes was the highest,and the number of differentially expressed genes was the largest.4 up-regulated and 4 down-regulated differentially expressed genes were selected for PCR verification.The results showed that the relative expression patterns of differentially expressed genes were consistent with the sequencing resuIts.And the expression of CONSTAANS-ZF1 and P450-2 genes were significant difference between trifoliate and multifoliate compound leaves of alfalfa.