| Alfalfa growing in Heilongjiang which overwintering rate low,frozen injury and even death.Based on the analysis of biological characteristics and cold resistances of Gongnong 1,Wega7F,WL319HQ,Aohan mixed with meadow fescue at 3:7 and were treated by 60COy-ray irradiation,ultraviolet,EMS and magnetic field-free space,which in order to improve the cold resistance of alfalfa by mixed sowing with meadow fescue and mutagenesis,meanwhile breeding of high yield,good quality and high hardy alfalfa.The major findings are as follows:1.The relationship between root morphology and cold resistances of alfalfa singly or mix-sowed with meadow fescueThe overwintering rate of alfalfa mixed-sowing with meadow fescue was much higher than single sowing respective alfalfa varieties.Root collar diameter,taproot diameter,lateral root number of mixed-sowing treatments had more higher than single sowing,but taproot length and crown depth in soil showed the reverse tendency.Root collar diameter increased at first and then decreased before overwintering,which from November 15th to April 30th did not change significantly.2.The relationship between root physiological indexes and cold resistances of alfalfa singly or mix-sowed with meadow fescueThe results showed that no matter either singly sowed or mix-sowed plants,physiological traits such as the soluble sugar,soluble protein,and free proline of the alfalfa roots increased as the temperature decreased at the end of autumn,and decreased when the air temperature increased in the spring.The Malondialdehyde(MDA)content and Peroxidase(POD)activity of all the treatments showed the trend of up-down-up during the whole overwintering stage.Investigation of the overwintering rate and using the membership function method combined with correlation analyses revealed that the order of the cold-resistance of the selected alfalfa cultivars were as follows:Gongnong 1+meadow fescue>Gongnongl>Wega7F+meadowfescue>Wega7F>WL319HQ+meadow fescue>WL319HQ>Aohan+meadow fescue>Aohan.3.Effects of different mutagens on alfalfa germination and seedling growth.Germination energy and germination rate was decreased with the dose of 60C-?-ray irradiation and ultraviolet increasing.Germination was inhibited by EMS and magnetic field-free space treatments.The root length and seedling length were promoted at first,which inhibited with the dose of 60CO?-ray irradiation increasing.Ultraviolet promoted root length,but inhibited seedling length,which were inhibited by EMS and magnetic field-free space.4.Effect of different mutagens on alfalfa agronomic traits150Gy 60COy-ray irradiation and 60min ultraviolet promoted plant height,but EMS inhibited it.Plant height of WL319HQ and Aohan were promoted,and the plant height of Wega7F and Gongnongl were inhibited by magnetic field-free space treatment.The branch number was increasing after the mutagenic treatments.The biomass increasing by 150Gy 60CO?-ray irradiation,60min ultraviolet and magnetic field-free space treatments.5.Effect of different mutagens on chlorophyll content and photosynthesisGongnongl treaded by 450Gy60COy-ray irradiation,Wega7F treaded by 60min ultraviolet,WL319HQ treaded by 0.4%EMS and Aohan treaded by magnetic field-free space,which chlorophyll content were highest.Photosynthetic rate was promoted that WL319HQ and Gongnongl treaded by 0.4%EMS,Wega7F treaded by 60min ultraviolet and Aohan treaded by magnetic field-free space.6.Effect of different mutagens on physiological characteristicsThe SOD,POD,CAT,MDA,soluble sugar,soluble protein and free proline were determined.The antioxidant enzyme activity was promoted by different mutagenic,mutagenic activity on three kinds of enzymes performance is POD>CAT>SOD.There was no significant effect on MDA.The content of energy metabolism matter,such as soluble sugar,soluble protein and free proline were improved by mutagenic.7.Effect of different mutagens on cell structure characteristicsThe microstructure of the leaf thickness of alfalfa was increased and the leaf vein protuberant degree was decreased by the different mutagenic.The ultramicrostructure of the chloroplast in the alfalfa leaves was observed under different mutagenic.Lower dose or concentration of mutagenic treatments,the chloroplast of the cell showed distortion,ambiguity in membrane,loose in grana lamella,disintegration in thylakoid,increases in lipid ball.Under the highest dose or concentration mutagenic treatment and magnetic field-free space,the chloroplast of the cell displayed swelling and distortion,fracture in grana lamella and disintegration in membrane system.Membrane systems of the chloroplast were disintegrated and its chloroplast structures were damaged more seriously,both plastids and starch grain were increased.In general,cold-resistance of alfalfa mix-sowed with the meadow fescue was higher than alfalfa singly sowing.150Gy60COy-ray irradiation,60min ultraviolet 0.4%EMS were the better mutagenic treatments that improve the cold resistance. |
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