Field Screening Traditional Rice Varieties Against Brown Spot Disease of Rice

Abstract

Brown spot of rice (BSR), caused by Bipolaris oryzae (Breda de Haan) Shoem., is one of the most destructive foliar diseases affecting rice production worldwide, particularly in India. The disease significantly reduces grain yield and quality, posing a major constraint to sustainable rice cultivation. Despite its economic importance, the unavailability of resistant cultivars continues to challenge effective management. Traditional rice varieties (TRVs) represent valuable genetic resources and are often rich reservoirs of genes conferring resistance to various biotic stresses. However, their potential as sources of resistance against BSR remains largely unexplored. The present investigation aimed to assess the resistance potential of 150 TRVs under field conditions at the All India Coordinated Rice Improvement Project (AICRIP) center, Agricultural Research Station (ARS), Gangavathi, Karnataka, India. Screening was conducted using artificial inoculation with a highly virulent isolate of B. oryzae (strain Bo-Gvt-01). Disease reactions were recorded at the maximum tillering stage following the Standard Evaluation System (SES) for rice. The results revealed a wide range of disease severity among the TRVs; however, none exhibited resistant or moderately resistant reactions to BSR, indicating a lack of effective resistance genes within the tested germplasm. The predominance of susceptible reactions underscores the vulnerability of existing traditional germplasm to B. oryzae infection. These findings highlight the urgent need to identify novel resistance sources from unexplored landraces, wild relatives, or induced mutants. Furthermore, integration of host resistance with eco-friendly and cost-effective management approaches, including cultural, biological, and integrated disease management strategies, is essential for the sustainable control of brown spot disease in rice.