| Drought is one of the main limited factors in maize production in China . The drought areas were more than 2300 ten thousand ha. in the year 2001, and maize is a kind of crop that needs much water, and is sensitive to water stressing among dry land crops , so drought has a greatly effect on maize yield. In Soirfhwest maize ecological region, one of the main maize production regions in China, most of the maize fields distribute on mountain and hill slopes with barren soil and rain-fed condition. Seasonal drought that often occurs during seedling emergence and milking stages causes significant loss of maize yield.There are two ways for resisting and defending drought and raising maize yield .One is to improve water equipment ,whose aim is to meet the need of plant living ;the other one is to develop the drought tolerance of maize. Comparing the two ways above, the later is a better one for breeding drought tolerance maize variety through identifying and screening maize germplasm materials of drought tolerance.The lowest soil moisture, the wilting coefficient of the sandy loam soil in the experiment field, under which drought tolerance inbred lines could germinate and grow was screened through pot experiment by controlling water in a plastic roof to prevent rainfall. High-quality seeds of the 57 experiment inbred lines popularized in China or newly bred were selected by germination test and sown. Soil moisture was controlled a little higher than wilting coefficient, the drought tolerance of 57 inbred lines was identified, and 15 indexes related to drought tolerance about growing and physiologic and biochemistry of 12 inbred lines were investigated. Drought tolerance coefficients were calculated, according to difference of drought compared with non-drought, and a multiple regression analysis was made with drought tolerance coefficient of per plant kernel yield as dependent variable.The result displayed there was a wide difference of drought tolerance in maize inbred lines. The coefficients of drought tolerance of Anthering and Silking interval and per plant kernel yield had a variance of 0.01~0.93 and 0.05~0.81. Such a big variance range of droughttolerance was just a potential for breeding drought tolerance variety.4 inbred lines with significant difference of drought tolerance were selected based upon the drought tolerance identification result of 57 inbred lines to make 6 generation group of PK P2> FK F2^ BK B2, in the same time 11 inbred lines with different drought tolerance were chosen to make 55 crosses according to complete diallel crosses of Griffing method 4. All the indexes with significant correlation to drought tolerance were investigated and transformed to drought tolerance coefficients to carry out the estimation of gene effect value and the related genetic parameters. All the experimental results are summarized below.1. Identification result of drought tolerance on 57 inbred linesThe drought tolerance of the 57 inbred lines could be divided into five levels according to their drought tolerant coefficients of per plant kernel yield. Level I: the strongest drought tolerance whose drought tolerance coefficients were over 0.8 only including 81565; Level II: the stronger drought tolerance whose drought tolerance coefficients were 0.61~ 0.80 including N87-1, R09 and 5 others; Level III :the middle drought tolerance whose drought tolerant coefficients were 0.61~0.80 including P3245-4, Ye52106 and 34 others; Level IV: weaker drought tolerance whose drought tolerance coefficients were 0.21~0.40 including L30> Zhong451 and 7 others; Level V: the weakest drought tolerance whose drought tolerance coefficients were under 0.20 including 21-ESx 200B, Dan340 and 9526.2. Screening of drought tolerance indexes identified during seedling stageThe multiple regression analysis of drought tolerances on 6 indexes identified during seedling stage with per plant kernel yield as dependent variable showed that the contributions of emergence rate and biomass to maize drought tolerance were very significa... |
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