ABSTRACT
Diversified population structures of major filamentous fungi evolved in specific rice intensive production systems. They are speedily analysed and accurately identified by molecular detection tools. If unchecked, pathogenic fungi may initiate disease epidemics that may pose a serious threat to the food security of over 800 million people across the tropical and sub-tropical climates. Several strategies, that are adopted worldwide, are integrated to develop an effective disease management system, are discussed. Crop losses can be minimized by appropriate crop husbandry practices such as exclusion of the pathogenic inoculum, stabilization of pathogenic virulence mechanisms, durable host plant resistance and recycle sources. These management strategies are vital keys to ensure production efficiency, stability of agricultural ecosystems, avoid fungicide resistance and advance research development and extension services for the future.
Rice blast caused by the ascomyceteous Magnaporthe oryzae and sheath blight caused by the necrotrophic soil-borne Rhizoctonia solani are the two most destructive diseases in rain-fed lowlands and dry upland ecologies where predisposing factors favour the development of epidemics. The dynamic evolution and adaptation of these pathogens have been challenging the effectiveness of deployed resistance genes in commercial cultivars and fungicidal compounds. Development of an effective and durable resistance requires a comprehensive understanding of the host-pathogen interaction, population structure and diversity, aggressiveness, pathogenesis, and pathogenecity of pathogen complex in different pathosystems. Durable resistance is attributed to a combination of complete and partial resistance and provides a broad spectrum of resistance. Detection of pathogen diversity and seed transmission of Bipolaris oryzae and Sarocladium oryzae have been addressed by PCR-based techniques. The long time debate on the pathogen infection process of false smut caused by Ustilaginoidea virens has been validated by cytological and molecular-based techniques. The view undergoing sexual reproduction in the field and a gene responsible for the production of mycotoxins by Fusarium fujikuroi and F. graminearum were detected by real time RT-PCR, which is an essential tool for assessing risk factors and crop losses and predicting the disease epidemics in order to develop a reliable disease management to produce high quality seeds. The management of other rice diseases such as sheath blight, brown leaf spot, narrow leaf spot, foot rot, stem rot and sheath rot are not discounted but crop husbandry practices and biological control are presented.
