Influence the weather parameters on sheath blight disease of rice

Introduction

Rice (Oryza sativa L.), a member of the family Poaceae, is one of the most important cereal crops grown in tropical regions. It can be successfully cultivated in both the wet and dry seasons, provided adequate water is available (Kawure et al., 2022) [4] . On a global scale, rice is cultivated over an area of about 162 million hectares. In India, the crop covers nearly 47 million hectares, producing around 132 million tonnes annually with an average productivity of 4.2 tonnes per hectare. In the state of Madhya Pradesh, rice is grown on approximately 3.4 million hectares, yielding about 12.3 million tonnes with an average productivity of 3.6 tonnes per hectare. Rice is attacked by a number of fungal, bacterial and viral diseases. Among the fungal diseases rice sheath blight is regarded as an internationally important disease. Sheath blight is a soil borne disease caused by the fungus Rhizoctonia solani Kuhn AG1-IA. Favorable temperature and evaporation rate results in 23.0 and 61.1% of disease incidence under field conditions, respectively (Lenka et al. 2008) [5] . The maximum progression of the disease is observed at the temperature range of 25°-33 °C and relative humidity of 80-100% (Thind et al. 2008) [8] . The fungus affects the crop from tillering to heading stage. Initial symptoms are noticed on leaf sheaths near water level on the leaf sheath as oval or elliptical or irregular greenish grey spots are formed. As the spots enlarge, the center becomes greyish white with an irregular blackish brown or purple brown border. This disease causes significant yield losses of about 11.1-58.0 percent depending on variety and stage of the crop (Chahal et al. 2003) [2] .

Methods and Materials

The in vitro experiments of present studies were carried out in the Department of Plant Pathology, JNKVV Jabalpur M.P. Effect of weather parameters on the initiation and progression of sheath blight of rice Kharif 2023-2024. The weather parameters was observed like Maximum Temperature (°C), Minimum Temperature (°C), Maximum Relative Humidity (%), Minimum Relative Humidity (%), Rainfall (mm), Rainy Days.

Progression of sheath blight disease incidence with weather Parameters

The progress of sheath blight of rice with different weather parameter variables was studies in two crop season kharif 2023 and kharif 2024 under field condition rice variety kranti (susceptible) was used in present investigation. During kharif 2023 the first observation was taken from 34 th standard metrological week till 45 th standard metrological week. The sheath blight disease incidence progressive increased during the observation of percent disease incidence varies from 8.36 to 45.96 percent during 34 th to 45 th standard metrological week. The progress of disease was relatively faster from 38 th to 39 th standard metrological week and 40 th to 41 th standard metrological week. The maximum temperature varies from 29.9 °C to 33.9 °C and minimum temperature varies from 13.9 °C to 24.5 °C. The morning Relative Humidity (%) varies from 73.4% to 92.7% and evening Relative Humidity (%) varies from 36.0% to 81.1% respectively. The rainfall varies from 9.2mm to 25.1mm and rainy days varies from 0 days to 5 days. During kharif 2024 the first observation was taken from 34 th standard metrological week till 45 th standard metrological week. The sheath blight disease incidence progressive increased during the observation of percent disease incidence varies from 10.29 to 48.20 percent during 34 th to 45 th standard metrological week. The progress of disease was relatively faster from 35 th to 36 th standard metrological week and 40 th to 41 th standard metrological week. The maximum temperature varies from 30.0 °C to 33.5 °C and minimum temperature varies from 16.1 °C to 25.4 °C. The morning Relative Humidity (%) varies from 87.9% to 93.6% and evening Relative Humidity (%) varies from 46.2% to 76.0% respectively. The rainfall varies from 0 mm to 184.8 mm and rainy days varies from 0 days to 3 days.

Correlation analysis

The result indicated that percent disease incidence was considerably influenced by the prevailing weather condition. During Kharif 2023, correlation coefficient between percent disease incidence and weather parameter viz., temperature maximum (0.140 NS ) shows non significant correlation, temperature minimum (-0.877 * ) shows negative significant correlation, Relative Humidity Morning (-0.753 NS ) shows negative non significant correlation, Relative Humidity Evening (-0.886 * ) shows negative significant correlation, Rainfall (-0.848 * ) shows negative significant correlation, Rainy Days (0.781 NS ) with percent disease incidence. During Kharif 2024, correlation coefficient between percent disease incidence and weather parameter viz., temperature maximum (0.123 NS ) shows non significant correlation, temperature minimum (-0.901 * ) shows negative significant correlation, Relative Humidity Morning (-0.695 NS ) shows negative non significant correlation, Relative Humidity Evening (-0.864 * ) shows negative significant correlation, Rainfall (-0.873 * ) shows negative significant correlation, Rainy Days (0.620 NS ) with percent disease incidence.

Discussion

Environmental factors play a crucial role in the development of sheath blight. Among meteorological parameters, temperature and relative humidity are the most critical in influencing the growth of the pathogen and disease progression. Yield losses due to sheath blight are significantly affected by factors such as host susceptibility, inoculum load, temperature, humidity, and rainfall. The progress of sheath blight disease in rice in relation to different weather parameters was studied during two Kharif seasons (2023 and 2024) under field conditions using the susceptible rice variety 'Kranti'.

Correlation analysis between weather variables and present disease incidence (PDI) revealed that minimum temperature and relative humidity were significantly negatively correlated with disease development, while all other weather parameters showed non-significant correlations. Similar findings were reported by Sindhu et al. (2023) [7] and Biswas et al. (2011) [1] , who observed that maximum air temperature was the most critical meteorological factor influencing sheath blight incidence under field conditions. After the disease was established, high temperatures (25.50-29.62 °C) were found to favor disease progression and spread. A minimum temperature around 26 °C was also conducive to further development of the disease. Furthermore, high relative humidity (above 90%) was found to support rapid disease transmission. Kaur et al. (2015) [3] reported that disease incidence and severity were positively correlated with morning relative humidity and sunshine hours, but negatively correlated with minimum temperature, evening relative humidity, and rainfall during both cropping seasons. Similar observations were made by Reddy et al. (2001) [6] .

Conclusion

The correlation coefficient analysis between percent disease incidence and weather parameters revealed the following: maximum temperature showed a non-significant correlation; minimum temperature showed a significant negative correlation; morning relative humidity exhibited a nonsignificant negative correlation; evening relative humidity showed a significant negative correlation; rainfall and number of rainy days both exhibited significant negative correlations with percent disease incidence.

References

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