| White clover is a high quality forage grass, which has wide ranges, strong ability to adapt and value in use. It can adapt to many kinds of soil, and can effectively resist to wet, barren, and cold. But drought and serious plant disease greatly limited its planting and promotion. In recent years, as the maturity of mutagenesis technology, mutation breeding was recognized and paid attention by more and more people. In order to research the effect of water stress on height, root length, above ground(underground) biomass., chlorophyll, water retention of leaves, relative water content, plasma membrane permeability, Pro, soluble sugar, SOD, POD, MDA; and the different effect of E.polygoin DC on two different varieties, this experiment in vitro selection and potted selection screened the drought tolerant mutants and the disease resistant mutants of White clover, which is mutagenesis by 60Co-y. The main results were as follows:1.To determine the suitable concentration, medial lethal concentration, and lethal concentration, four materials of White clover Rivendel variety were selected with mannitol in vitro screening. Then the mutants were identified by measuring height, root length, biomass, chlorophyll, MDA, Pro, SOD, POD, and compared the difference between the mutation materials and the original materials. Besides, four materials’drought tolerance were evaluated by using the standard deviation coefficient of weight method; nine drought resistance indexes of materials were selected by principal component analysis. The results showed that 20Gy mutagenic materials and 80Gy mutagenic materials had higher medial lethal concentration and lethal concentration than original material. Through comprehensive evaluation, the drought tolerance order of four materials from strong to weak was 20Gy,90Gy,80Gy, OGy. It meant the drought tolerance of all mutagenic materials were stronger than original material. The principal component analysis showed that nine drought-resistance indexes were synthesized into three comprehensive indexes, which represented 96.6%of original information. The first comprehensive index mainly included the ground biomass, Pro and SOD; the second comprehensive index mainly included the underground biomass, height, MDA and POD; the third comprehensive index mainly included chlorophyll.2.The cutting seedlings of mutagenic White clover Haifa variety by 6 Co-y were treated with water stress about 21d, which had grown about 64d in pots. Then the mutants were evaluated by measuring the ground(underground) fresh-weight, the ground(underground) dry-weight, chlorophyll, relative water content, water retention of leaves, MDA, electrical conductivity, soluble sugar, Pro, and compared the difference between the mutation materials and the original materials. Besides, materials’drought tolerance were evaluated by using the standard deviation coefficient of weight method; eleven drought resistance indexes of materials were selected by principal component analysis. The results showed that 97 mutants were selected from 120 materials. The treatment group’s the ground(underground) fresh-weight, the ground(underground) dry-weight, chlorophyll, relative water content were lower than control group; and its water retention of leaves, MDA, soluble sugar, Pro, electrical conductivity were higher than control group. In addition to chlorophyll and water retention of leaves, materials had significant difference(P<0.05). Through comprehensive evaluation, a total of 41 mutagenic materials’ comprehensive value were greater than original material Ⅲ. It meant the drought tolerance of 41 materials were stronger than original material, and selecting 4 extremely drought tolerance materials(Ⅲ40-1, Ⅲ70-2, Ⅲ70-3, Ⅲ70-5). The principal component analysis showed that eleven drought-resistance indexes were synthesized into three comprehensive indexes, which represented 85.23%of original information. The first comprehensive index mainly included the ground(underground) fresh-weight, the ground(underground) dry-weight; the second comprehensive index mainly included chlorophyll; the third comprehensive index mainly included electrical conductivity.3.The cutting seedlings of mutagenic White clover Haifa variety and Cllilkanova variety by Co-y were treated with artificial inoculation E.polygoin DC, which had grown about 64d in pots. Then the results showed that the disease index of Haifa variety distributed between 30.18%-62.16%, and most of mutagenic materials’ disease index were lower than original material Ⅲ, which disease index was 62.05%, except Ⅲ3-10;the disease index of Cllilkanova variety distributed between 72.58%～81.31%, and half of mutagenic materials’ disease index were lower than original material V, which disease index was 75.83%. Compared Haifa variety and Cllilkanova variety, the latter were easier infected E.polygoin DC and serious occurred, which disease index were greater than 72%. |
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