Genetic variation in fifty-three maize inbred lines in relation to drought tolerance at seedling stage

Chinese. 了解53份玉米自交系的苗期耐旱性，挖掘耐旱玉米种质。采用幼苗叶片相对含水量、叶片保水力和叶片丙二醛含量，结合水分胁迫下的幼苗存活率，评价了53份玉米自交系的苗期耐旱性，筛选出耐旱系13份、中等耐旱系16份和旱敏感系24份。在水分胁迫下，耐旱系的叶片相对含水量较高、叶片保水力强、丙二醛含量低，胁迫解除后，植株能恢复生长。随着胁迫强度增大，旱敏感系的叶片保水力下降、叶片相对含水量和丙二醛含量迅速降低，复水后植株不能恢复生长。叶片相对含水量和保水力是玉米耐旱性的重要指标，可用于评价玉米自交系的苗期耐旱性。利用63对SSR引物分析了53份自交系的遗传多样性，共检测出245个等位基因变异，平均多态性信息量为0.596。结合系谱资料和育种实践将53份自交系划分为Lancaster、BSSS、旅大红骨、PA、四平头和PB共6个亚群。除Lancaster外，其余5个亚群均含有耐旱系。根据自交系的耐旱性反应，发现BSSS、PB和四平头亚群的幼苗存活率、叶片相对含水量和保水力较高，为重要的耐旱种质类群。采用t测验，在8份耐旱系和10份旱敏感系间检测出21个具有显著频率差异的等位基因，可用于玉米自交系苗期耐旱性评价。BSSS、PB和四平头亚群为重要的耐旱种质类群。检测出的21个具有显著频率差异的等位基因，可用于玉米自交系苗期耐旱性评价。

English. Drought is a potential major constraint to maize stable production. Identification of drought-tolerant germplasms in seedling stage is an efficient way to exploit useful genes. In this study, using leaf relative water content, leaf water conservation, MDA content and seedling survival rate as standard indexes, 53 inbred lines were evaluated for drought responses in greenhouse under water-stressed and well-watered conditions during 2005 in Beijing, China. The evaluation resulted in identification of 13 drought-tolerant, 16 moderately tolerant and 24 susceptible inbred lines, respectively. Under water-stressed condition, drought tolerant lines were found to show higher relative water content, water conservation and lower MDA content, while the cases reversed for drought susceptible lines. Leaf relative water content and water conservation were two important traits indicating drought responses at seedling stage in maize. The diversity at DNA level was investigated applying 63 SSR markers. The total number of alleles was 245, and the mean of polymorphism information content was 0.596. The UPGMA analysis showed that 53 inbred lines could be classified into six sub-groups (Lancaster, BSSS, PA, Luda Red Cob, Sipingtou and PB), which were generally consistent to their known pedigree records and other breeder’s experiences. Comprehensive differences were observed on mean leaf relative water contents, leaf water conservation and seedling survival rate among the six sub-groups. The levels for BSSS, Sipingtou and PB were found to be relatively high. BSSS, Sipingtou and PB were identified as the important sources of drought tolerance. 21 SSR alleles were significantly associated with drought tolerance, which could be employed for evaluating the inbred lines of maize to drought responses at DNA level.