Genetic diversity among some important Syrian wheat cultivars was estimated using Amplified Fragment Length Polymorphism (AFLP) markers. Five Triticum aestivum L. and 10 Triticum turgidum ssp. durum were analyzed with 11 EcoRI-MseI primer pair combinations. Of the approximately 525 detected AFLP markers, only 46.67% were polymorphic. Cluster analysis with the entire AFLP data divided all cultivars into two major groups reflecting their origins. The first one contained T. aestivum L. cultivars, and the T. turgidum ssp. durum cultivars and landraces were grouped in the second. Narrow genetic diversity among all cultivars was detected with an average genetic similarity of 0.884. The lowest similarity index (0.9) was found between Cham5 and Hamary (durum wheat), whereas this value was 0.93 between Salamony and Bouhouth 4 (T. aestivum L.). The narrow genetic diversity level indicates that these genotypes could be originated from the same source. AFLP analysis provides crucial information for studying genetic variation among wheat cultivars and provides important information for plant improvement.

Fusarium head blight (FHB) is consistently one of the most important barley diseases worldwide. This study aimed to evaluate the pathogenicity of 16 isolates of four Fusarium species under controlled conditions and their genetic variability using 22 random amplified polymorphic DNA (RAPD) markers. Pathogenic variation was characterized based on disease development rates and disease index on two Syrian barley landraces with varying resistance to FHB, Arabi Aswad (AS) and Arabi Abiad (AB). Significant differences in intra- and inter-Fusarium species pathogenicity and in susceptibility between the above-mentioned cultivars were highlighted. Overall, the two barley landraces showed moderately susceptible to moderately resistance levels to fungal infection and FHB spread within the head. Quantitative traits showed significant correlation with previous data generated in vitro and under field conditions, suggesting that growth chamber indices can predict fungal pathogenicity and quantitative disease resistance generated under various experimental conditions. Based on PCR amplification with seven different primers, the isolates showed genetic variation. Dendrogram generated by cluster analysis based on RAPD markers data showed two main groups, suggesting that a possible clonal origin could exist in the four Fusarium species. RAPD fingerprints are not useful to distinguish the 16 Fusarium isolates with different levels of pathogenicity.

Leaf scald caused by the infection of Rhynchosporium secalis, is a worldwide crop disease resulting in significant loss of barley yield. In this study, a systematic sequencing of expressed sequence tags (ESTs) was chosen to obtain a global picture of the assembly of genes involved in pathogenesis. To identify a large number of plant ESTs, which are induced at different time points, an amplified fragment length polymorphism (AFLP) display of complementary DNA (cDNA) was utilized. Transcriptional changes of 140 ESTs were observed, of which 19 have no previously described function. Functional annotation of the transcripts revealed a variety of infection-induced host genes encoding classical pathogenesis-related (PR) or genes that play a role in the signal transduction pathway. The expression analyses by a semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) revealed that Rar1 and Rpg4 are defense inducible genes, and were consistent with the cDNA-AFLP data in their expression patterns. Hence, the here presented transcriptomic approach provides novel global catalogue of genes not currently represented in the EST databases.

Spot blotch, caused by Cochliobolus sativus, is an important barley disease which causes extensive grain yield losses worldwide. In order to investigate the molecular responses to the C. sativus infection, leaf transcriptome and proteome before and after fungus inoculation in a resistant barley genotype, were compared using cDNA-AFLP and 2-D PAGE techniques. A notable number of transcripts and proteins exhibiting significant differential accumulations were detected compared to the non-inoculated controls. Functional annotation of the transcripts and proteins revealed a wide range of pathways including cell wall fortification, metabolism, signal transduction and defence. Spearman correlations of the relative abundances for those genes represented by both an mRNA and a protein showed a weak (r s = 0.4; P < 0.001) relationship, indicating that post-transcriptional processes play a critical role in regulating the protein level during infection. Taken together, our study suggested that a joint analysis of the transcriptomic and proteomic of barley data can provide useful insights that may not be deciphered from individual analysis of mRNA or protein expressions.

The biotrophic Blumeria graminis (Bg) and the necrotrophic Cochliobolus sativus; (Cs) are economically important fungal pathogens of barley globally. To better understand barley mechanisms to resist these pathogens, changes in salicylic acid (SA) and its responsive genes particularly the pathogenesis related PR1, PR2, PR3 and PR5 were evaluated using qRT-PCR across four time points post infection. Data showed that SA contents significantly increased (P = 0.001) in infected plants of both resistant and susceptible genotypes 24 h post inoculation in comparison with non-infected controls. In addition, time-course tests revealed a notable contradiction in the defense-related genes expression patterns between barley and Bg and Cs interactions, showing that expression patterns of the same defense-associated genes were altered in adaptation to different pathogens. PR1 and PR2 genes were highlyactivated inresistant plants infected with the necrotrophic pathogen Cs rather than of the biotrophic one. The uniformity in barley defense response mechanisms could be in convention with the well-accepted notion that these responses are high intense in the resistant genotype. Our work provides useful information on the expected role of SA pathways in barley towards biotrophic and necroptrophic pathogens with different lifestyles.