| The alfalfa anti-thrips new strain was breed by a forage breeding group in Inner Mongolia Agricultural University, using the breeding method of the clone multiplication and the recurrent selection,through mone than ten years. It have been planted experimentally in the Huhhot peripheral locality continuously several year. The various characters, such as adaptability and agronomic traits had a good performance, and the anti-thrips was strong. Besides, the new alfalfa strain had the remarkable enhancement compared to these local existing alfalfa varieties in the grass crop and the quality aspect.Several alfalfa varieties (Medicago sativa var. Caoyuan No 2, M. sativa var.Aohan, M. sativa var.Algonquian and so on) planted in large area of the east, the middle and the west in Inner Mongolia, with the new strin were used to study their agronomic performance and the thrip resistance, and anlysis the anti-thrips mechanismmid of the new strain. The main results are as follows:1.Thrips damage and thrips distributed characterestics in the field: the result indicated that the level distribution of the thrips in the field were 30×40~30×50cm2 mottling, the major axis was the east and west direction ellipse; The vertical direction mainly distributed 20cm scope in the upside.2. Leaf trichome density of new strain and feeding habits of thrips: the results showed that the new strains of anti-thrips alfalfa leaf trichome density of the new strain distributed the area that less than 10 / mm2, occupied 9.6% of leaflet total area; the area of 10 / mm2 ~ 16 / mm2 accounted for 62.6% of leaflet total area; the area of 16 / mm2 was more than 29%. This means that the area of higher density occupied large proportion than the other strains. The harm point coefficient is 0.25, was lower 16% than the lowest in the comparision. The new anti-thrips strain had the fewer access points, short feeding time compared to the other strains for the thrips feeding behavior. So the resistance of new strain was stronger than the other strains. The choice of rate of thrips to anti-thrips new strain was lower 13% than other varieties.3. The result of agronomic characters research indicates that the hay production and the protein production of the new strain was higher 0.7%~3.3% and 15.9%~19.1% than other 3 strains, including Medicago sativa var. Caoyuan No 2 resprectively.The character , such as the number of various strains branching, the proportion of stem and leaves, plant height, stem diameter and live through the winter character , were not evidence.4. The results of physiologic and biochemistry characters for new strain showed that the enzyme activity, such as POD, SOD, PAL, PPO, CAT, for the new strain changed as qucikly, so the plant could adjust themselves and resume their normal growth and development; but fhe enzyme activity of MDA and proline changed slowly, that is to say relative hazard of thrips is small; The SA content of the new strains changed faster than other strains, and the initial content was high. It could get higher concentrations of SA when the leaves against thrips, and higher concentration of SA would around wound. The histiocyte that infect by other pathogenic bacteria putresce rapidly, result in pathogens died because the loss of suitable environment for the survival, no longer infect new cells around and prevent the expansion of the wound, thus reducing the post-production factors caused by thrips harm; The isozyme analysis showed that increase varieties of protective enzyme content or activity of anti-thrips alfalfa strains could be further confirmed that various indicators of measured activity and the analysis results was coherent.5. molecular marker analysis results indicated that 12 primers simple sequences differed with other 4 strains were selected from the new strain. So the certain genetic differences could existed among the new strain and other various varieties.
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