Analysis Of Genetic Structure In Backcross Population Of Multifoliate Alfalfa

Multifoliate alfalfa has higher leaf/stem ratio, and has the potential to enhance and improve current quality of alfalfa. In the field observation, mulitifoliate alfalfa’s branches is less and height is small, so to improve other traits of multifoliate alfalfa become this research target. The Huaiyin alfalfa of Jianghuai region’s local varieties (nonrecurrent parent) and the PL34HQ of Nan’ao multifoliate alfalfa strains(recurrent parent) were parents in this experiment, and were used to build the strengthen F1 poptlation and backcross BC1 population by artificial pollination. Comparison analysis of alfalfa types of different compound leaves between 116 individuals of the BC1 population and 90 individuals of the F1 population, and analysis of the agronomic characters, the genetic diversity and population structure of the BC1 population, were to understand the genetic characteristics of improvement for multifoliate alfalfa, and the excellent plants or group were chose from the BC1 population, serving as the subsequent breeding material. The main results are as follows:1. Plant proportion of compound multifoliate types (’4+5’,’4+5+6’and’4+5+6+7’compound leaf types) containing four leaves and five leaves in the BC1 population was higher than that in the F1 population; 16.67% of the plant was four leaves type of multifoliate type in the F1 population and multifoliate type was single.2. Analyzd relational degree of alfalfa types of different compound leaves in the BC1 population, showed alfalfa type of’4+5+6+7’ compound leaves had the biggest relational coefficients, and comprehensive performance of agronomic traits of this type was better.3. The average values of agronomic traits were less than the mid-parent value in the BC1 population. The dry weight of single plant was extremely significant positive correlation with the plant height, the plant branches, and was significant positive correlation with the stem/leaf ratio in the BC1 population. The correlation coefficient of various characters with the dry weight of single plant from high to low were the plant branches, the plant height, stem/leaf ratio, fresh/dry ratio, multifoliate rate of main branch and multifoliate rate of single plant.4.25 pairs of primer were detected 137 allelic variation in the BC1 population, and 5.48 to per primer; variation range of the polymorphism ratio were 60% to 100%, the average polymorphism ratio was 81.59%, and variation range of the gene diversity were 0.1517 to 0.4063, the average gene diversity was 0.2869. Variation range of PIC were 0.6344 to 0.9604 in 25 pairs of primer, the average PIC was 0.8600.5.106 individual plants (Q≥0.5) of the BC1 population were divided into four groups, the remaining 10 individual plants (accounting for 8.62% of the total) was for mixed groups. Change rule of the genetic diversity and Shannon index were consistent. In the BC1 population, analysis of the multifoliate traits of four groups indicated, Group 1 had the highest multifoliate rate of single plant, was significantly higher than Group 2 and 3, and was no significant difference with Group 4; Group 4 had the highest multifoliate rate of main branch, was significantly higher than Group 2 and 3, and was no significant difference with Group 1; Multifoliate rate of population of Group 4 was the highest in four groups. There were no significant differences in the plant height, the plant branches, the stem/leaf ratio, and the dry weigh of four groups. Group 4 had the highest fresh/dry ratio, was significantly higher than Group 1.