| Drought is one of the main factors limiting maize production in China. In Southwest maize ecological region, one of the three major maize production regions of China, most of maize fields distribute on mountain and hill slopes with barren soil and rain-fed irrigation. Seasonal drought that often occurs during seedling emergence and milking stages makes significant loss of maize yield. The areas of drought were more than 2300 ten thousand ha. in the year 2001,and maize is a crop that need much of water, and is sensitive to water stressing among dry land crops, so that drought have effected yield of maize. There are two ways for resisting and defending drought and raising yields of maize, one is to improve water ecologic environment, the aim is to meet the need of plant living; the other way is to develop the ability of maize, which make plant's drought tolerant improving and reach stable yield. Comparing with two ways above, the later is benefit way for breeding maize variety of drought tolerance through filtering and identifying maize germplasm materials of drought tolerance.The lowest soil moisture (7.5 %) under which drought tolerant inbred lines could germinate and emerge was screened through pot experiment by control watering and used as the wilting coefficient of the sandy loam soil in the experiment field. High-quality seeds of the 57 inbred lines that have been popularized in China or bred newly in recent years were selected by germination test and sown in a plastic roof to prevent rainfall. Soil moisture was controlled, which the content of moisture is little higher than wilting coefficient, the drought tolerance of 57 inbred lines was identified, and 15 indexes related with drought tolerance about growing and physiologic and biochemistry of 12 inbred lines were investigated. According to difference of drought compared with non-drought, drought tolerant coefficients were calculated, and a multiple regression analysis with drought tolerance coefficient of per plant kernel yield as dependent variable was made. The result shown, there are big difference of drought tolerance in maize inbred lines. The coefficients of drought tolerance of Anthering and silking interval and per plant kernel yield have a variance of 0.01-0.93 and 0.05-0.81. Such as big variance range of drought tolerance just is potential of breeding drought tolerance variety. The results are exactly28summarized below.7.1 Identification result of drought tolerance of 57 inbred linesThe drought tolerance of 57 inbred lines can be divided five classes , inbred line of 81565 is the strongest drought tolerant variety , that drought tolerance coefficient of per plant kernel yield is over 0.8; 7 inbred lines (N87-1. R09 and so on ) are second level, and drought tolerance coefficient are 0.61 ~0.80; 36 inbred lines (P3245-4, Ye52106 and so on) are middling drought tolerant varieties that drought tolerance coefficients of per plant kernel yield are 0.41~0.60. 9 inbred lines ( L30, zhong451 and so on) are weaker drought tolerant varieties that drought tolerance coefficients of per plant kernel yield are 0.21~0.40. the last of 4 inbred lines (21-ES, 200B, Dan340 and 9526) are the weakest drought tolerant varieties that drought tolerance coefficients of per plant kernel yield are under 0.20.7.2 Screening of drought tolerance indexes identified during seedling stage Through multiple regression analysis of drought tolerances about 6 indexes identifiedduring seedling stage with per plant kernel yield, the result shown: the contributions of emergence rate and biological output to drought tolerance of maize were very significant. It indicated, under drought condition, the more level of emergence rate and biological output is high, the more drought tolerance of maize is strong. On the contrary, drought tolerance is weak.7.3 Screening of drought tolerance indexes identified during grown up stage Through multiple regression analysis of drought tolerances about 9 indexesidentified during grown up stage with per plant ker...
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