| Drought is one of the important factors that constraints maize production in China. When drought stress occurs just before or during flowering period, a delay in silking is observed, resulting in an increase in the length of ASI and a severe decrease in grain yield. Under drought condition, searching for some secondary traits that have high heritability and correlate to grain yield, and constructing selection index may provide a working alternative to improve the efficiency of breeding towards better drought tolerance. In this paper, molecular marker technique and QTL mapping method were used to identify genetic segments conferring the expression of flowering and yield components; to examine the consistence of detected QTLs over environments; to determine if QTLs for Anthesis-silking interval or filament fertility could be used in Marker-Assisted-Selection (MAS) for improvement of grain yield under drought conditions in temperate maize.In this study, a F2 population with 184 individuals, derived from a cross of Huangzao 4XYel07, is used to construct a SSR genetic map, and locate QTLs for conferring anthesis, silking, ASI, ear setting percentage and grain yield. The results are summarized as follows:(1) Ninty-nine SSR primers were" used in analyzing genotypes of the F2 population, and the allele frequencies of Huangzao4 and YelOV were 50.59% and 49.05%, respectively. Chi-square test indicated that 12 markers loci (5.88%) skewed from the expected gene segregation (1:2:1). Thirty-three markers (32.53%) skewed from the expected genotypic segregation. A genetic linkage map is constructed using 102 polymorphic loci, covering 1543cM on total ten chromosomes with an average interval length of 17.3cM.(2) Under well-watered condition, 9 QTL involved in the expression of anthesis were detected on chromosomes 1, 3, 4, 5 and 7; 8 QTL for silking were detected on chromosomes 1, 3,4, 5, 6, 7 and 10; and 6 QTL for ASI were mapped on chromosomes 1, 2, and 3. respectively. Under drought stress, 8 QTL for anthesis were identified on chromosomes 1, 4, 5, 6, 9 and 10; 4 QTL for silking were detected on chromosomes 3, 4 and 10; and 4 QTL for ASI were identified on chromosomes 2, 3, 5 and 9. respectively. For the three flowering traits, each QTL detected could explain around 5.8% to 39.8% phenotypic variance, and the gene action was partial dominant or over-dominant. Under two water regimes, the QTL detected for each trait was different, but some stable QTL could be detected.(3) Under well-watered regime. 2 QTL involved in the expression of ear setting percentage were detected on chromosomes 3 and 6. and the gene action were additive and partial dominant effects, respectively. 2 QTL could totally explain about 19.9%-56-phenotypic variance. Under drought stress, 4 QTL for ear setting percentage were detected on chromosomes 3, 1 and 10, and the gene action were dominant and partial dominant effects, respectively. 4 QTL could interpret 60.4% phenotypic variance. Under well-watered condition, 4 QTL controlling grain yield were identified on chromosomes 3, 6 and 7; while 5 QTL were identified under drought stress, which were on chromosomes 1, 2, 4 and 8. The gene action was additive and partial dominant effects, and each QTL could explain 7.3% to 22.02% phenotypic variance, respectively.(4)In two sites and two water regimes, the linear correlation between ASI and silking, or silking and anthesis were all highly significant (P<0.01), but the linear correlation between ASI and anthesis was not significant except Shanxi water-stressed. In Shanxi, the linear correlation between anthesis, silking, ASI, ear setting percentage with grain yield were all significant (p<0.05), and the linear correlation coefficient between ear setting percentage and grain yield was very high (0.62) under well-watered .(5) Under drought conditions, ASI and ear setting percentage can be used as the secondary traits for grain yield selection. Based on linked markers detected and gene action analysis, the selection st...
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