New threats to rice production: emerging pathogens and their impact

Authors: PEDROZO, RODRIGO - Oak Ridge Institute For Science And Education (ORISE); DEPAULA, SAMUEL - University Of Arkansas; DALLA LANA, FELIPE - Louisiana State University; FLASCO, MADISON - Louisiana State University; Jia, Yulin; NICOLLI, CAMILA - University Of Arkansas

Submitted to: IntechOpen
Publication Type: Book / Chapter
Publication Acceptance Date: 6/3/2025
Publication Date: 7/9/2025
Citation: Pedrozo, R., Depaula, S., Dalla Lana, F., Flasco, M., Jia, Y., Nicolli, C. 2025. New threats to rice production: emerging pathogens and their impact. IntechOpen. Book Chapter.

Interpretive Summary: Rice feeds more than half of the world's population, making it one of the most important crops on the planet. However, rice farmers face many challenges, especially from diseases caused by viruses, bacteria, and fungi. These diseases can significantly destroy the crop yearly, threatening food security and farmer livelihoods. This book chapter looks at new and reemerging rice diseases that are becoming more common and harder to control. One virus, the Rice hoja blanca virus, disappeared from the U.S. for 65 years but recently returned, causing concern. Another troublemaker is Pantoea ananatis, which can infect rice in many ways, especially when the weather and environment change. Fungal diseases like narrow brown leaf spot and rice false smut are also increasing, but aren't fully understood yet, especially how they spread and how to stop them. Scientists are working to understand better these threats, where they occur, how they infect plants, how they spread, and what can be done to manage them. This information is essential for developing better tools to protect rice crops through breeding, more innovative use of pesticides, and new farming practices.

Technical Abstract: Rice (Oryza sativa) is a staple food for over 50% of the global population. Biotic and abiotic stresses contribute to yield losses in rice cultivation, estimated at 10-30% annually. Among these, plant diseases are major constraints, typically managed through genetic resistance, pesticide application, and cultural practices. However, pathogen evolution, vector dynamics, rising disease incidence, and shifts in geographic distribution have led to the emergence of diseases once considered minor threats. Rice hoja blanca virus is of particular concern due to the complexity of the rice-virus-vector interaction. After a 65-year absence, this virus reemerged in the United States, affecting a large area, though its distribution is likely underestimated. Another emerging pathogen is Pantoea ananatis, a globally distributed bacteria noted for its ecological plasticity and variable rice symptom expression influenced by environmental conditions. Despite its first report over two decades ago, the mechanisms underlying infection, colonization, and symptom development in rice remain poorly understood. Similarly, the narrow brown leaf spot and rice false smut, both fungal pathogens, have shown increasing incidence in recent years. Substantial knowledge gaps persist in their life cycles, hindering effective management. More specifically, rice false smut exhibits a unique floral infection strategy and remains largely unaddressed in breeding programs, with fungicides providing only limited suppression. This chapter focuses on the pathogen distribution and characterization, symptomatology, epidemiology, detection methods, and management strategies for these emerging rice pathogens, highlighting critical areas for future research.