Powdery mildew of wheat and its management
134Powdery mildew caused by Blumeria graminis f. sp. tritici is the fourth most important disease of wheat after three rusts. It inflicts yield losses to the tune of 13–34% and 50–100% under low or moderate infestation and severe infestation, respectively. It is essential to understand the damaging trend, etiology, virulence pattern, host resistance, genetics of host resistance, and fungicidal management for its successful control. Molecular studies on host–parasite interaction of wheat-powdery mildew system are continuously being conducted resulting in identification and mapping of resistant genes. Currently, ~80 designated resistance alleles have been identified at 51 loci (Pm1-Pm55, Pm18 = Pm1c, Pm22 = Pm1e, Pm23 = Pm4c, Pm31 = Pm21, Pm48 = Pm46). In addition, <50 resistance genes have been located but carry temporarily designated nomenclature. Use of molecular markers such as simple sequence repeat (SSR), amplified fragment length polymorphism (AFLP), restriction fragment length polymorphism (RFLP), random amplified polymorphic DNAs (RAPD), and sequence tagged sites (STS) has contributed to identification and mapping of many resistant genes. Fungi- cidial sprays have been successfully applied as a shorterm alternative for its management. In this chapter damages caused by wheat powdery mildew, virulence structure of the pathogen in epimeological important areas, identification of resistant sources, postulation of racespecific resistant genes, major resistance genes and molecular markers flanking the resistant genes, and fungicdal management of the disease have been reviewed.