Epidemiological Factors in Relation to Development of Alternaria Blight of Rapeseed - Mustard

Abstract

Alternaria blight is one of the most widespread and destructive diseases of rapeseed-mustard, cause highly yield loss 15-71 per cent in productivity with 14-36 per cent decrease in oil content. The development and severity of the diseases are greatly influenced by prevailing Meteorological parameters particularly temperature, relative humidity and rainfall play major role in the development of Alternaria blight disease. The investigation was undertaken to study the Epidemiology of Alternaria blight under field conditions during rabi the 2020 -21 and 2021-22 crop season, and findings were subsequently validated using data from two additional cropping seasons. Eighteen rapeseed -mustard cultivars, namely Bhawani, Pusa Bold, Varuna, Rohini, Kranti, Krishna, Vardan, Vasundhara, Pusa Jyoti, Pusa Mahak, Swarn Jyoti, Pusa Jai Kisan, Albely, Sej-2, Shradha, Kiran, Pusa Vijay and Anmol were evaluated for diseases development under natural epiphytotic conditions. The epidemiological analysis revealed that diseases progression varied significantly among cultivars and was strongly associated with fluctuations in weather parameters. Among the meteorological parameters, minimum temperature, maximum humidity was found positively and strongly correlated with Alternaria blight in each rapeseed-mustard genotypes and maximum temperature, association of evaporation with development of the Alternaria blight in each mustard genotypes were seen as negative and highly significant. Meteorological parameters, minimum temperature exhibited significant to highly significant association with development of the Alternaria blight. The stepwise regression analysis revealed that out of six variables three variables maximum temperature, maximum relative humidity and minimum relative humidity were found suitable for explaining variation in intensity of Alternaria blight. The regression model as significant and was Y = - 23.71 - 0.41 (maximum temperature) + 0.3536 (maximum relative humidity) +0.10 (minimum relative humidity). The R square value of the model was 0.9020, which means 90.20% of the variation present in disease intensity was explained by maximum temperature, maximum relative humidity, and minimum relative humidity. The findings provide valuable insights into the role of weather factors in diseases development and may assist in forecasting diseases outbreaks and formulating effective management strategies for Alternaria blight of rapeseed – mustard.