Genetic Variation In Relation To Drought Tolerance In Chinese Maize Inbred Lines And QTL Identification At Seedling Stage

In the study, the genetic variation in 53 maize inbred lines in relation to drought tolerance was characterized using leaf relative moisture content, leaf water conservation, MDA content and seedling survival rate. Fifty-three 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 moisture contents, water conservation and lower MDA contents, while the cases reversed for drought susceptible lines. Leaf relative moisture content and water conservation were two important traits indicating drought responses at seedling stage in maize.The diversity at DNA level was investigated by 63 SSR markers. The total number of alleles was 245, and a mean polymorphism information content was 0.596. The UPGMA analysis showed that 53 inbreds could be classified into 6 subgroups (Lancaster, BSSS, PA, Luda Red Cob, Sipingtou and PB), which were generally consistent to their known pedigree records and breeder's experiences. Comprehensive differences were observed on the mean of leaf relative moisture contents, leaf water conservation and seedling survival rate among the six sub-groups with relatively high level for BSSS, Sipingtou and PB. These three sub-groups were identified as the important sources of drought tolerance. Twenty-one SSR marker alleles were significantly associated with drought tolerance, which could be employed for evaluating the inbred lines of maize to drought responses at DNA level.In this paper,screening of 28 (BC2F1) resulted in a total of 683 surviveing BC2F1 plants from 8400 interogression lines (ILs) under the drought stress that killed the recurrent parents (RPs). We found that the selection efficiency was largely diffence in 28 BC populations. The results indicated that althought most parents didn't show drought tolerance, there were transgressive segregations in most BC populations for the drought tolerance (traits), suggesting these favorable alleles are"hidden"in the donors. Using SSR molecule marker and graphical genotype method to analyze BC populations (Chang7-2×CA156 and Ye478×B73) found that average each individual plant carrying 17 and 13 introgressed segments, and each chromosome carrying 47 and 34 introgressed segments. Take advantages of both linkage and linkage disequilibrium (LD) mapping principle to identify and mapping seedling QTL, there were 38 QTLs in 2 BC populations, in which seven independent loci(Bin 1.09,5.00,5.06,7.01,7.02,8.00,10.02 ) were associated with SSR marker alleles associated with drought tolerance , and also five loci (2.04,2.07,6.05,6.07,9.04) were associated with"universal drought tolerance QTL"(QTL UQ2-1,UQ2-2,UQ6-1,UQ6-2,UQ9-1).