| Drought stress poses a serious threat to maize growth and production. In China, the maize germplasm resources with drought tolerance are relatively poor, so identification of drought tolerant varieties from maize inbred lines and its wild relatives have great importance in broadening maize germplasm resources and drought tolerant maize breeding. This study evaluated the drought tolerance among twelve teosinte lines, three distant hybridization populations and two maize recombinant inbred lines (RIL) populations using the morphological, physiological and biochemical features under drought condition and identifed drought tolerant germplasm. The main results from this study were as follows:1. The evaluation of drought tolerance in twelve teosinte lines. The NDVI value, SPAD value, relative water content, relative electrical conductivity, free proline content, soluble sugar content, MDA content and SOD activity of teosinte were measured under the well water (WW) and water stress (WS) condition for 30 days. The results showed that NDVI value, SPAD value, relative water content, free proline content, soluble sugar content and SOD activity in teosinte had a positive correlation with drought tolerance in plants, while relative electrical conductivity and MDA content had a negative correlation with drought tolerance. SPAD value showed the hysteresis effect and the other traits showed compensation effects or super compensation effects during the process of re-watering after the drought stress. We analyzed the comprehensive evaluation value of drought resistance (D value) in different teosinte lines, and found that each teosinte line performed differently in drought tolerance. Zea nicaraguensis and Zea luxurians were extremely drought resistant; Z. mays subsp. Huehuetenangensis, Zea diploperennis and Zea perennis were moderate drought resistant; Z. mays subsp. Mexicana was drought-sensitive; Z. mays subsp. Parviglumis showed dramatic diversity among varieties with different drought tolerance. In addition, five drought resistant teosinte lines and three drought sensitive teosinte lines were selected from the twelve teosinte lines to evaluate their drought tolerance with increased drought stress intensity (60 days of drought stress treatment). According to the average subordinative function value of each trait, we identified two extremely drought resistant materials and two extremely drought sensitive materials. The two extremely drought resistant materials were Zea luxurians (No.7 teosinte) and Z. mays subsp. Parviglumis (No.12 teosinte), respectively, while the two extremely drought sensitive materials were Z. mays subsp. Parviglumis (No.1 and No.2 teosinte).2. The evaluation of drought tolerance at seedling stage of three genetic populations constructed by the distant hybridization of maize inbred lines (R15,178, Zheng58) and Z. mays subsp. Mexicana. Leaves mortality and the plant mortality at seedling stage were measured after 70 days of drought stress treatment. The results showed that the drought tolerance of R15×Z. mays subsp. Mexicana population was stronger than 178 × Z. mays subsp. Mexicana and Zheng58 × Z. mays subsp. Mexicana populations. We divided these three populations containing 377 materials into four groups using cluster analysis. The four groups named the group ?, ?, ? and ?, showed decreased drought tolerance, containing 46,108,133 and 90 materials, respectively. The group ? was extremely drought resistant, the group ? and ? were the medium drought resistant, and the group ? was extremely drought sensitive.3. The evaluation of drought tolerance at seedling stage of two maize RIL populations (C5 and C6 populations). Dry weight, moisture content, growth amount, leaves mortality, SPAD value and plant mortality at seedling stage of recombinant inbred lines were measured under well water (WW) and water stress (WS) condition for 40 days. We found that the correlations between each trait were significant except for the correlations between SPAD value and dry weight or growth amount. Heritability of each trait we tested was medium or medium high, and the drought tolerance characters of recombinant inbred lines were well reflected by the traits we measured. Drought tolerance of the C5 population was slightly stronger than the C6 population. According to the comprehensive evaluation value of drought resistance (D value), we divided the two maize RIL populations into three groups, including the drought resistant group, the moderate drought resistant group and the drought sensitive group. Among them, the drought resistant groups of the C5 and C6 RIL populations included 20 and 18 recombinant inbred lines, respectively, while the drought sensitive groups included 18 and 20 recombinant inbred lines, respectively. |
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