Virulence Analysis of Wheat Powdery Mildew (Blumeria graminis f. sp. tritici) and Effective Genes in Middle Delta, Egypt.

Wheat powdery mildew (Blumeria graminis f. sp. tritici) has increased in Delta Egypt in recent years as a result of growing susceptible cultivars of bread wheat. Fifty-two isolates of B. graminis f. sp. tritici collected in 2013 and 2014 from commercial fields in five provinces were analyzed for virulence, using 21 genes conferring resistance to powdery mildew (Pm genes) as well as 12 local wheat cultivars. First true leaves of 10-day-old wheat differentials were inoculated with isolates derived from a single pustule of B. graminis f. sp. tritici. No virulence to the resistance genes Pm3d, Pm12, Pm16, Pm24, Pm35, Pm36, and Pm37 was detected, indicating that these genes could be used for resistance breeding. Virulence to Pm2, Pm4a, and Pm6 was low, while high virulence to genes Pm1a, Pm3a, Pm3c, Pm3f, Pm5a, Pm7, Pm8, Pm9, and Pm17 was found, indicating that breeders should be very cautious in using these genes. At the adult stage, genes Pm2, Pm3d, Pm3f, Pm4a, Pm6, Pm12, Pm16, Pm17, Pm24, Pm35, Pm36, and Pm37 were completely effective in both years. All the tested Egyptian wheat cultivars were susceptible under natural field conditions. The virulence of B. graminis f. sp. tritici population and resistance Pm genes have been assessed for the first time in Egypt.

Developing transgenic wheat to encounter rusts and powdery mildew by overexpressing barley chi26 gene for fungal resistance.

BACKGROUND: The main aim of this study was to improve fungal resistance in bread wheat via transgenesis. Transgenic wheat plants harboring barley chitinase (chi26) gene, driven by maize ubi promoter, were obtained using biolistic bombardment, whereas the herbicide resistance gene, bar, driven by the CaMV 35S promoter was used as a selectable marker. RESULTS: Molecular analysis confirmed the integration, copy number, and the level of expression of the chi26 gene in four independent transgenic events. Chitinase enzyme activity was detected using a standard enzymatic assay. The expression levels of chi26 gene in the different transgenic lines, compared to their respective controls, were determined using qRT-PCR. The transgene was silenced in some transgenic families across generations. Gene silencing in the present study seemed to be random and irreversible. The homozygous transgenic plants of T4, T5, T6, T8, and T9 generations were tested in the field for five growing seasons to evaluate their resistance against rusts and powdery mildew. The results indicated high chitinase activity at T0 and high transgene expression levels in few transgenic families. This resulted in high resistance against wheat rusts and powdery mildew under field conditions. It was indicated by proximate and chemical analyses that one of the transgenic families and the non-transgenic line were substantially equivalent. CONCLUSION: Transgenic wheat with barley chi26 was found to be resistant even after five generations under artificial fungal infection conditions. One transgenic line was proved to be substantially equivalent as compared to the non-transgenic control.