Study On Biological And Physiological Characteristics Of 6 Alfalfa Materials

Alfalfa(Medicago sativa)is a perennial herbaceous legume.In the north of China,climate and other reasons pose a certain threat to alfalfa growth,especially the problem of safe overwintering of alfalfa.Therefore,it is an important goal of alfalfa breeding to improve the cold resistance and overwintering ability of alfalfa to adapt to the planting conditions in high latitudes,and the development of new germplasm resources is an effective way to solve this contradiction.In this paper,the remaining alfalfa plants after cold weather were screened.On April 16,2017,seedlings were raised in the greenhouse in Qianbuhong Village,Wuyuan County,and a single plant was transplanted to the field in mid-June.Using random block design.To evaluate theses alfalfa materials,we observed its biological characteristics,agronomic characters and resistance indexes and explored the relationship between multiple indicators.In order to screen out the superior materials with strong cold resistance,high productivity and excellent nutritional quality,and to provide new germplasm resources for alfalfa breeding.The results are as follows:1.The autumn dormancy grade and cold resistance index of 6 materials were evaluated.The results showed that the autumn dormancy grades of No.1,No.2 and No.3 are grade 1,which belong to autumn dormancy material,and the autumn dormancy grade of material No.4 and No.6 are grade 6 and grade 4,respectively,which are semi-autumn dormancy material.The autumn dormancy grade of No.5 material was grade 8,which belonged to non-autumn dormancy type,and the other materials were all autumn dormancy type.Correlation analysis shows that autumn dormancy grade was positively correlated with cold resistance index and negatively correlated with overwintering rate.2.The analysis of plant structure of 6 alfalfa materials showed that the distribution of total biomass of alfalfa at all levels was irregular rhombic structure,which belonged to the upper type of forage grass.Alfalfa materials No.1,No.3 and No.4 have good straightness,good plant type structure,high yield and high quality potential.The stem of No.2 and No.6 materials is creeping and high density planting will seriously affect the yield and quality.The biological yield was positively correlated with plant height,plant weight,branch number,stem diameter and stem length,and the yield of alfalfa material No.4 and No.6 with the highest stem length,stem diameter and single plant weight was also higher in the first year.In this study,the hay yield of different stubble is different.The first hay yield accounted for about 40% of the total annual hay yield.3.The dry-fresh ratio and crude protein content of No.3 and No.6 materials were significantly higher than those of other materials,and the CP content and RFV of forage grass at budding stage were significantly higher than those of other cutting stages.With the prolongation of growth period to pod setting stage,the contents of NDF and ADF of forage grass increased significantly.4.The contents of soluble sugar,starch,sucrose,glucose,fructose,raffinose and stachyose increased at first and then decreased with the growth and development of Medicago sativa,and the accumulation of carbohydrates in different organs was different.The contents of soluble sugar,starch and sucrose were mainly stored in the root.Glucose,raffinose and stachyose were mainly distributed in the leaves,while the fructose content was more in the stem,followed by the leaves and the least in the roots.Carbohydrates rise and fall many times throughout the year,showing "V" type.The total sugar content decreased most obviously in the returning green stage(April 7)and seed setting stage(June 20).Starch decreased sharply at the end of autumn(October 30)and during the seed setting period(June 20).The highest values of fructose and glucose content appeared before the green period(February 28),flowering stage(June 13)and when the weather turned cold(October 30).This is closely related to the growth and development of plants.5.The contents of MDA,soluble protein and free proline in roots increased significantly during overwintering period,and the contents of MDA in roots were negatively correlated with the cold resistance of alfalfa.The contents of free proline and soluble protein in alfalfa roots were the highest in the middle winter and decreased when it turned green in spring.The correlation between soluble protein and cold resistance of alfalfa was small.