Insights into the host-pathogen interaction of emerging disease, seed discoloration in rice: Losses, pathogenomics, and management strategies

Seed discoloration other than called grain discoloration in rice is an emerging serious threat to global rice production. It is characterized by a change on the seed coat color due to fungal infestation which causes a decline in seed quality, germination potential, crop establishment, milling quality and market value. It is a complex disease mainly caused by different genera of fungi such as Fusarium spp., Bipolaris spp., Alternaria spp., Curvularia lunata , Sarocladium oryzae, and Aspergillus etc . Several other saprophytic fungi and pathogenic bacteria like Burkholderia glumae are also associated with the disease. The severity of infection is highly influenced by the environmental factors like high moisture and temperature fluctuations coupled with rainfall. It also results in reduced nutritional qualities like starch and protein content, increased phenolic compounds, reduced vigour, overall crop establishment and storability. Understanding the pathogen biology, epidemiology and host-pathogen interaction will help in formulating integrated disease management (IDM) measures like cultural, chemical, biological, and genetic methods to effectively reduce the losses. There is still limited understanding of host-pathogen interactions, pathogen/s associated with the disease, scanty information on host plant resistance mechanisms. The current review compiles available information on the origin, economic impact, symptoms, causal organisms, associated mycotoxins and their effect on plant physiology and finally, integrated management strategies. • Seed discoloration is emerging as a major problem of rice. • The disease causes significant yield and quality losses. • The disease reported to cause nutritional, biochemical and milling quality of rice thus leading to non-preference of the consumers in the market. • A comprehensive research work needed to address these basic issues so that, efficient management measures can be formulated.