Improvement Effect Of Multifoliate Traits On Alfalfa By Backcross

Multifoliate Alfalfa(Medicago sativa L.)have the potential to improve the yield and quality.In this paper,the backcross population is constructed by using multifoliate alfalfa and trifoliate alfalfa as parents.At the same time,the changes of multifoliate character of F1 generation alfalfa obtained by different breeding methods are observed,and the growth character and the variation of multifoliate character in growth stages are studied.Then,the multifoliate alfalfa of different compound leaf types are compared.Combined with the regeneration of alfalfa in summer and autumn,the grey relational degree of dry weight per alfalfa plant is analyzed.Then general combining ability analysis is carried out on trilobites and leafy plants in backcross population.The purpose of this paper is to systematically describe the improvement of multifoliate character of alfalfa after backcross and to explore its general combining ability.In order to provide high quality materials with high combining ability for the improvement of multifoliate character.The main research results are as follows:(1)The multifoliate rate of single plant and population of backcross population BC,and BC2 are significantly higher than that of F1 generation plants.Among them,the multifoliate rate of population of F1,BC1 and BC2 populations are 55.03%,69.73%and 76.27%,respectively.In the four growth periods in spring,the multifoliate rate of single plant showed a decreasing trend,while the multifoliate rate of population generally increased first and then decreased.In F1,BC1 and BC2 populations,the multifoliate rate of single plant significantly decreased from vegetative growth period to bud growth period,from initial flowering period to bearing pod stage,the declines ranged from 4%to 7%and from 13%to 15%.However,multifoliate rate of population increased significantly from the vegetative growth period to the bud stage,and decreased significantly from the initial flowering stage to the pod setting stage.(2)By comparing the progeny populations of F1 generation alfalfa obtained by different breeding methods.The multifoliate rate of single of F2 generation is significantly lower than that of BC1 and S1 populations.The multifoliate rate of single plant and population is the highest in S1 population.However,due to the difficulty of alfalfa self-crossing,the S1 population plants obtained by self-crossing are also the least among the three populations.The plant height,branching number and dry weight per plant of F2 population are the highest among the three populations.The performance of the three groups in each growth period is similar to that of F1 and BC2 groups,all of which showed a decrease in multifoliate rate of single plant,and a decrease after the first increase in multifoliate rate of population(3)Comparing the leaf areas of leafy plants of different compound leaf combinations.The leaf area of triclobular compound leaves will decrease with the increase of compound leaf combination type per plant,only 6.14 cm2 in type 4+5+64-7 alfalfa.At the same time.the leaf area of 7 lobules and compound leaves is larger than that of other types of plants,14.98 cm2.According to the formula of weighted correlation degree,4+5+6+7 alfalfa had the best agronomic traits.(4)The comparison of regeneration character of alfalfa population in summer and autumn indicated that the optimal cutting period of alfalfa in summer is the early flowering period,and the optimal cutting period in autumn is when the temperature is above 10℃.The comparison of the regeneration character of the four alfalfa populations showed that the regeneration character are close in summer,and the regeneration rates of S1 and BC1 populations with higher multifoliate rate decreased later and the regeneration curves are.more gentle in autumn.At the same time,through the analysis of grey correlation degree,the fresh dry ratio is the largest influence on alfalfa dry weight per plant,followed by plant height,multifoliate rate of single plant and regenerated plant height in summer(5)Through 6 backcrossing alfalfa parents,18 two-row hybrid combinations are constructed for general combining ability determination.The results showed that,among the 6 backcross parents,the effect value of combining ability of single plant multi-leaf ratio as parent in the backcross population is higher,which could be used for breeding of multi-leaf traits.The total combining ability of the parents of trifoliate plants is high and has high value.At the same time,the correlation between the general combining ability and the phenotypic value of plant height,branch number and leaf multiplicity per plant is significant.