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Rheinischen Friedrich-Wilhelms-Universität zu Bonn (2011)

QTL Analysis for Drought Tolerance Related to Root and Shoot Traits in Barley (Hordeum vulgare L.)

Mohammed Abd El-Aziz Abd El-Haliem Sayed

Titre : QTL Analysis for Drought Tolerance Related to Root and Shoot Traits in Barley (Hordeum vulgare L.)

Auteur : Mohammed Abd El-Aziz Abd El-Haliem Sayed

Université de soutenance : Rheinischen Friedrich-Wilhelms-Universität zu Bonn

Grade : Doktor der Agrarwissenschaften (Dr. agr.) 2011

Résumé
Enhancement of drought tolerance of cultivated barley via identifying the potential and beneficial QTL alleles of wild species (H. vulgare ssp. spontaneum C. Koch) is a great target in barley breeding. Therefore, the overall objectives of the proposed study were : 1) to assess variations in shoot, root and physiological traits of BC2DH lines under control and drought stress conditions. 2) to localize and characterize the QTLs underlying drought tolerance related to shoot, root and physiological traits. Mapping was conducted using a combination of phenotypic data of three investigated years and 371 DNA markers. This investigation was done under control and drought stress conditions. Components of variance revealed a wide range of variability for majority of the investigated traits. In total, 79 putative QTLs for 15 studied traits were detected among 5,565 marker by trait combinations in the population S42 under study. They can be divided into 55 QTLs for shoot traits, 15 QTLs for root traits and 9 QTLs for physiological traits. Overall 27 (34.1 %) QTLs showed favorable effects derived from the presence of exotic alleles. Most of putative QTLs were located on chromosomes 1H, 2H, 4H and 5H. For instance, two QTLs (QWS.S42.1H and QWS.S42.4H) had favorable effects due to the presence of the exotic alleles (Hsp) that were responsible for decreasing plant wilting score by 17%. The SSR markers GMS3 [2H], HvNAM2 [2H] and M1o [4H] were associated with QTLs are likely to be dominating number of tillers/plant and number of spikes/plant and the introgressions from wild barley may increase both traits in S42 population. Also for root length, the vernalisation gene VrnH1[5H] was associated significantly with the QTL (QRL.S42.5H). The presence of exotic alleles at this marker locus led to increase root length by 9.17 % under drought conditions. For proline accumulation, the superior performance of exotic allele at marker locus MGB338 on chromosome 5H suggests a transgression effect of the exotic alleles and led to increase proline content BC2DH lines carrying Hsp alleles by 53% under drought conditions. The majority of the digenic epistatic interaction pairs which were detected in current study had favorable effects in enrich the phenotypic values of the studied traits. Interesting, these exotic QTL alleles responded favorably under drought conditions only that indicates the possibility of underlying a novel drought inducible gene. This study has highlighted the role of the exotic alleles for the detection of favorable leads for drought tolerance. Subsequently, a combinatory approach for the selection of favorable exotics alleles can be employed to develop a better shield against the adverse effects of drought.

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Page publiée le 8 novembre 2011, mise à jour le 12 mai 2019