Molecular characterization of genetic variation in somaclones of durum wheat (Triticum durum Desf) using SSR markers

This study is a continuation of a previous work; the main objective is to characterize the induced somaclonal variation in the first generation of durum wheat plants. In a previous experiment, in vitro plants of three genotypes of durum wheat were obtained following treatment with PEG6000 (0%, 10% and 20%). First generation offspring was produced. Five microsatellite markers were used for genotyping 26 durum wheat somaclones obtained under stressful and non-stressful conditions from 3 durum wheat cultivars. Amplifiable and reproducible alleles were obtained in three of the tested loci. These loci provided in total 78 monomorphic alleles of which 69 were detected in somaclones while the remaining 9 in the mother plants. High values of among-population genetic diversity were found, which accounted for 71 % of the total genetic variation. The number of alleles per locus varied from three to six. Estimated genetic distances varied from 0.83 to 1.67 between populations. The somaclonal variation was identified with 2 SSR markers. Five new alleles were identified in somaclonal variants DKR1-S1, DKR1-S2, OZR1-S2, WR1-C3 and WR1-S1at loci gmw131 and gwm427. Genetic variation rate was 21.74%. Eighty % of the genetic variation was identified in plants obtained from callus undergoing high osmotic pressure. The presence of selective agent in the medium could explain the observed genetic variations. Somaclonal variation cannot always be detected at the gross morphological level. The selected SSR markers could be used to study the uniformity of plants obtained from tissue culture and varietal identification

Molecular and genetic characterization of Fusarium head blight resistance in winter wheat Centenaire

Fusarium head blight (FHB) is a devastating disease of wheat (Triticum aestivum L.) with worldwide economic and health impact caused by a group of trichothecene producing Fusarium species with Fusarium graminearum being the most prevalent. Breeding wheat resistant to FHB is one of the best strategies to minimize crop and grain quality losses due to the pathogen. However, the numbers of reported FHB resistance sources are limited including mostly spring genotypes and as well the molecular events leading to FHB resistance are still poorly understood. In the present work, we initiated a study on molecular and genetic characterization of FHB-resistant winter wheat genotype Centenaire exhibiting Type II resistance. The molecular aspect of this thesis was identification and characterization of putatively candidate defense genes expressed in Centenaire during F. graminearum infection using suppression subtractive hybridization. Forty three differentially expressed sequences were identified as up-regulated in the resistant germplasm due to the infection in the first 72 hours post-inoculation. Time-course expression study confirmed that some of the newly identified transcripts were differentially expressed between resistant and susceptible wheat accessions and they were related to metabolic pathways with potential role in resistance. Thirty out of forty three gene candidates were assigned to the corresponding wheat chromosomes and several were localized in the regions known to harbor quantitative trait loci for head blight resistance. In the present thesis we reported the identification of five new full-size ATP-binding cassette transporters G (ABCG) subfamily differentially expressed in wheat genotypes with contrasting resistance to head blight. The obtained results emphasize the potential involvement of ABCG transporters in wheat resistance to FHB, at least in part through the detoxification of the pathogen-produced mycotoxin deoxynivalenol. In addition, evidences that ABCB and ABCC transporter subfamilies may be also involved in resistance mechanisms were shown. Molecular markers were used to study the genetic basis of the quantitative resistance to FHB in wheat population B360 derived from cross between Centenaire x Robigus and consisting of 148 individual lines. Considering marker segregation data and phenotypic observation for each line from population B360 in different environments allowed us to identify eight microsatellite markers on chromosomes 1B, 2B, 3A, 4B, 5A and 6B linked to quantitative trait loci for FHB resistance. The results presented in this work point out possible molecular mechanisms involved in resistance to head blight. Identification of microsatellite markers linked to quantitative trait loci for FHB resistance propose winter genotype Centenaire as a source for head blight resistance with possible use in wheat breeding programs.(BIOL 3) -- UCL, 201

Identification, characterization and mapping of differentially expressed genes in a winter wheat cultivar (Centenaire) resistant to Fusarium graminearum infection.

Fusarium head blight (FHB), predominantly caused by Fusarium graminearum, is a destructive disease that poses a serious threat to wheat (Triticum aestivum L.) production around the world. A suppression subtractive hybridization (SSH) cDNA library was constructed from F. graminearum infected spikes of a resistant Belgian winter wheat variety Centenaire, exhibiting Type II resistance to FHB. Forty-three differentially expressed transcripts were identified and classified in different categories according to their predicted function, including proteins involved in defense response, signaling, transport of molecules, metabolism and proteins with unknown function. Time-course gene expression analysis between the FHB resistant genotype Centenaire and the susceptible genotype Robigus was carried out on twelve selected genes in order to validate the SSH screening. Real-time quantitative polymerase chain reaction showed that the selected transcripts were differentially expressed between the resistant and the susceptible genotype at three-time points (24, 48 and 72 h) after inoculation with the pathogen, and mostly, the transcripts accumulation rates were higher in the FHB-resistant as compared to the susceptible one. Thirty identified differentially expressed loci were mapped on the corresponding wheat chromosomes either by in silico analysis or by PCR-based mapping strategy, and fifteen of these loci were located within or nearby chromosomal regions known to have quantitative trait loci for FHB resistance in winter wheat cultivars. This work emphasizes the differential gene expression between the FHB-resistant winter wheat Centenaire and the susceptible Robigus and highlights the putative genes and mechanism involved in the disease resistance reaction

Gene expression profiling by cDNA-AFLP reveals potential candidate genes for partial resistance of 'Président Roulin' against Venturia inaequalis

BACKGROUND: Scab, caused by the fungus Venturia inaequalis, is one of the most important diseases of cultivated apple. While a few scab resistance genes (R genes) governing qualitative resistance have been isolated and characterized, the biological roles of genes governing quantitative resistance, supposed to be more durable, are still unknown. This study aims to investigate the molecular mechanisms involved in the partial resistance of the old Belgian apple cultivar ‘Président Roulin’ against V. inaequalis. RESULTS: A global gene expression analysis was conducted in ‘Président Roulin’ (partially resistant) and in ‘Gala’ (susceptible) challenged by V. inaequalis by using the cDNA-AFLP method (cDNA-Amplified Fragment Length Polymorphism). Transcriptome analysis revealed significant modulation (up- or down-regulation) of 281 out of approximately 20,500 transcript derived fragments (TDFs) in ‘Président Roulin’ 48 hours after inoculation. Sequence annotation revealed similarities to several genes encoding for proteins belonging to the NBS-LRR and LRR-RLK classes of plant R genes and to other defense-related proteins. Differentially expressed genes were sorted into functional categories according to their gene ontology annotation and this expression signature was compared to published apple cDNA libraries by Gene Enrichment Analysis. The first comparison was made with two cDNA libraries from Malus x domestica uninfected leaves, and revealed in both libraries a signature of enhanced expression in ‘Président Roulin’ of genes involved in response to stress and photosynthesis. In the second comparison, the pathogen-responsive TDFs from the partially resistant cultivar were compared to the cDNA library from inoculated leaves of Rvi6 (HcrVf2)-transformed ‘Gala’ lines (complete disease resistance) and revealed both common physiological events, and notably differences in the regulation of defense response, the regulation of hydrolase activity, and response to DNA damage. TDFs were in silico mapped on the ‘Golden Delicious’ apple reference genome and significant co-localizations with major scab R genes, but not with quantitative trait loci (QTLs) for scab resistance nor resistance gene analogues (RGAs) were found. CONCLUSIONS: This study highlights possible candidate genes that may play a role in the partial scab resistance mechanisms of ‘Président Roulin’ and increase our understanding of the molecular mechanisms involved in the partial resistance against apple scab. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/1471-2164-15-1043) contains supplementary material, which is available to authorized users

Identification and differential induction of ABCG transporter genes in wheat cultivars challenged by a deoxynivalenol-producing Fusarium graminearum strain.

Fusarium head blight (FHB), predominantly caused by Fusarium graminearum, is a devastating disease that poses a serious threat to wheat (Triticum aestivum L.) production worldwide. A suppression subtractive hybridization cDNA library was constructed from F. graminearum infected spikes of a resistant Belgian winter wheat, Centenaire, exhibiting Type II resistance to FHB in order to identify differentially expressed members of full-size ABCG family. Members of the ABCG family are pleiotropic drug transporters allowing the movement of structurally unrelated metabolites, including pathogens-derived virulent compounds, across biological membranes and could be potentially involved in resistance to plant pathogens. In this study, five new full-size ABCG transporter expressed sequence tags TaABCG2, TaABCG3, TaABCG4, TaABCG5 and TaABCG6 have been identified. Time-course gene expression profiling between the FHB resistant Centenaire and the susceptible Robigus genotype showed that the newly isolated transcripts were differentially expressed up to 72 h-post inoculation. The respective genes encoding these transcripts were mapped to corresponding wheat chromosomes or chromosomal arms known to harbor quantitative trait loci for FHB resistance. Interestingly, these ABCG transcripts were also induced by deoxynivalenol (DON) treatment of germinating wheat seeds and the toxin treatment inhibited root and hypocotyl growth. However, the hypocotyl of the FHB resistant cultivar Centenaire was less affected than that of the susceptible cultivar Robigus, reflecting more likely the genotype-dependent differential expression pattern of the identified ABCG genes. This work emphasizes the potential involvement of ABCG transporters in wheat resistance to FHB, at least in part through the detoxification of the pathogen-produced DON

Abortive seed development in common bean (Phaseolus vulgaris L.)

peer reviewe