An active role of systemic fungicides to curb wheat powdery mildew caused by Blumeria graminis f. sp. tritici
Keywords:Wheat, Powdery mildew, Fungicide activity, Blumeria graminis f. sp. tritici, SEM examination
Efficacy of five systemic fungicides (flusilazole, propiconazole, diniconazole, cyproconazole and tetraconazol) in curbing powdery mildew disease of wheat (Sakha93) and its impact on yield components were evaluated under field condition during two successive season. Both fungicides, propiconazole and diniconazole exhibited the highest value of efficacy (88.80% each) recording the lowest rate of disease infection (1 each). The contrast was noticed with tetraconazol (55.50% efficacy, 4 disease infection) with significant differences to untreated control during both seasons. The results of fungicide application reflected on yield components where 1000-kernel and 1000-ml weights recorded the highest values with propiconazole (49.03 g and 742.65 g) followed by diniconazole (47.69 g and 737.62 g), respectively. Tetraconazol come in the last order in this respect (44.39 g and 672.07 g). An active role of fungicide (propiconazole) on Blumeria graminis f. sp. tritici was examined on infected wheat leaves (8-day old seedlings) by scanning electron microscopy (SEM). To investigate the effect on early develop of conidia, fungicide was applied at 24 h post inoculation (hpi), and collapsed conidia along with blocked development beyond the primary appressoria were observed. Where conidia germinated, appressoria formed two or three lobes. To investigate the effect on fungal morphogenesis, applying of fungicide at 2 day post inoculation (dpi) greatly reduced the mycelium formation associated with a rapid collapse of hyphae compared with untreated control. Fungicide treatment at 10 dpi inhibited and delayed sporulation alongside formation of aberrant and collapsed conidiophores. The conidiophores formed elongated tubes with no regular or sepatated chain of conidiospores. Results concluded that fungicide is an efficient curative fungicide at very low concentrations if it is applied early enough after infection. Also, fungicide has a significant impact on fungal survival.