Infection process of Blumeria graminis f. sp. poae BGP(TG) on the leaves of Poa pratensis with different resistance

Abstract:

[Background] Poa pratensis powdery mildew caused by Blumeria graminis f. sp. poae is an airborne disease, and planting resistant species is the most economical, environmentally friendly, and effective method for controlling this disease. [Objective] To observe the infection process of BGP(TG) on the leaves of three P. pratensis species with different resistance and clarify the role of papillae in the resistance of P. pratensis to powdery mildew. [Methods] Coomassie brilliant blue staining was combined with microscopy to observe the infection process of BGP(TG). The rate of secondary germ tube formation and the formation of haustoria and effective papillae in the three species were determined. [Results] The powdery mildew symptoms in ‘Explorer’ were more serious than those in the other two species, and the infection process of BGP(TG) was similar in different species. However, the formation of primary haustoria on the leaves of ‘Explorer’ was earlier than that of the other two species. One- or two-days post inoculation with BGP(TG), the formation of fifth-level germ tubes on the surface of ‘Taihang’ was slower than that of ‘Explorer’ and ‘Black Jack’. One day post inoculation with BGP(TG), more effective papilla was formed on ‘Taihang’ than on ‘Black Jack’, and the effective papilla formation rate on ‘Black Jack’ was higher than that on ‘Explorer’ (P＜0.05). [Conclusion] This study clarifies the infection process of B. graminis f. sp. poae and provides a theoretical basis for the prevention and control of powdery mildew in P. pratensis.