Epidemiology and prevalence of rice sheath rot disease under foothill conditions of Nagaland

Abstract

Despite being a major staple food crop, rice (Oryza sativa L.) of the Gramineae family is plagued by several diseases, one of which is sheath rot (Sarocladium oryzae W.) causing significant yield and economic losses. The study was conducted in Nagaland during kharif 2022 to screen 27 rice genotypes along with one resistant check variety against rice sheath rot disease under natural field conditions. Disease identification was done based on field symptom expression, followed by pathogen isolation and microscopic examination of morphological characteristics. Results of screening revealed that among the tested genotypes, only three were immune, eight resistant, ten moderately resistant and six moderately susceptible to sheath rot disease. The highest mean disease incidence (44.17 %), disease severity (30.86 %) and area under disease progress curve (AUDPC) values (371.57) were recorded in genotype Apuapa, whereas the lowest in Thangmo, Thupfu Lha and Chali as no disease symptoms were observed. In addition to factors like susceptible cultivars, meteorological conditions also significantly contributed to disease development and spread. So, for epidemiological study, the correlation analysis revealed a significant positive correlation between sheath rot severity and maximum relative humidity while temperature and minimum relative humidity showed negative correlations. Simple regression analysis showed that among the weather parameters, maximum relative humidity with R2 value of 0.878 influenced sheath rot severity of up to 87 %. These findings may support future breeding programmes focused on developing resistant cultivars, as well as improving crop loss prediction for sustainable disease management and yield protection.