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Universitäts Bonn (2004)

Improving crop varieties of spring barley for drought and heat tolerance with AB-QTL-analysis

Mohammed, Khalaf Ali Hamam

Titre : Improving crop varieties of spring barley for drought and heat tolerance with AB-QTL-analysis

Auteur : Mohammed, Khalaf Ali Hamam

Université de soutenance : Universitäts Bonn, Landwirtschaftliche Fakultät

Grade : Doktorgrade 2004

Résumé
In the years 2002-2003, 323 BC2DH individuals of double haploid (DH) spring barley population were genotyped with SSRs markers. The BC2DH lines were evaluated in greenhouse trials for drought and heat tolerance. Altogether 13 parameters for the determination of drought tolerance and 12 parameters for the investigation of heat tolerance were examined. There were two treatments for the drought experiment, 50% field capacity (FC) level for drought stress and at 100% FC level for the control. We used two treatments for the heat experiment (normal climate and in greenhouse). The traits measured were : relative leaf water content, osmotic adjustment, heading date, number of spikes per plant, number of kernels per spike, number of leaves per main tiller, flag leaf area, first leaf area, second leaf area, carbon isotope discrimination (for the drought experiment), yield, biomass and harvest index. The traits were compared to determine the presence of alleles from the wild barley parent by means of the AB-QTL-analysis. The 97 mapped SSRs covered 1013 cM of the barley genome ; the mean SSR density is equal to 11.1 cM. Polymorphic SSRs revealed 54 putative QTLs in two groups. The first had 20 putative QTLs for the drought experiment and the second 34 putative QTLs for the heat experiment. Altogether, 30 (55.5%) favorable allele effects of the Hsp alleles were detected for both drought and heat experiment. 14 (70.0%) favorable effects were detected for drought tolerance. These traits, osmotic adjustment, yield, biomass, relative leaf water content, carbon isotope discrimination, number of leaves per main tiller and flag leaf area were controlled by 7, 3, 3, 3, 2, 1 and 1 QTL respectively, in the drought experiment. Most of the favorable Hsp alleles were located on chromosomes 1H, 5H and 7H (2, 8 and 3 respectively). Under drought stress first leaf area was positively and strongly correlated with flag leaf area. Positive correlations were expressed by second leaf area with flag leaf area and first leaf area. Yield was positively correlated with harvest index, number of spikes per plant and number of kernels per spike. Biomass showed correlations with number of spikes per plant, number of leaves per main tiller, flag leaf area, first leaf area, second leaf area and yield. 16 (47.0%) favorable effects of the Hsp alleles were detected for heat tolerance. Flag leaf area, osmotic adjustment, yield, harvest index, biomass, first leaf area, relative leaf water content, number of spikes per plant and heading date were controlled by 8, 7, 4, 4, 3, 3, 2, 2 and 1 QTL respectively, in heat experiment. Most of the QTLs were located on chromosomes 3H and 4H (3, and 5 respectively). Correlations of heading date with osmotic adjustment, and number of leaves per main tiller were strongly positive. Strong positive correlations were expressed by second leaf area with flag leaf area and first leaf area. Yield was positively and strongly correlated with harvest index.

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