Effect of Weather Parameters on the Severity of Bacterial Leaf Blight of Rice (cv. Basmati-370)

Author: Tabasia Amin, Vishal Gupta, Aarushi Singh and Sheikh Saima Khushboo

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Abstract

Weather conditions significantly influence the plant disease incidence and development. Rainfall, temperature, relative humidity, flood and cyclonic conditions are the important factors for disease development. High humidity (>80%), rain and cloudy conditions accelerate the disease development in bacterial leaf blight of rice. A moderate and evenly distributed rainfall during the crop season can bring about an epidemic. Temperature is an important environmental factor influencing plant development in natural and diseased conditions in BLB. Disease appeared on 31st SWM during both the years with disease severity of 1.03 and 1.47 percent. Terminal severity of BLB was recorded as 44.13 and 45.45 per cent, when the crop was at harvest stage during 46th SMW during both the years of 2019 and 2020. During the epidemiological studies of BLB, maximum infection rate (r) of 0.175 (Basmati-370) was observed during 32nd standard week (2019) and, maximum infection rate (r) of 0.164 was observed during 33rd standard week (2020). AUDPC of BLB was 293.19 and 305.27 in 2019 and 2020, respectively. During 2019, temperature (Max. and Min.), relative humidity (evening), rainfall and bright sunshine hours showed significant but negative correlation with severity of BLB, whereas, relative humidity (morning), showed positive correlation with disease. Whereas, during 2020, temperature (Max. and Min.), relative humidity (morning), relative humidity (evening) and rainfall showed significant but negative correlation with severity of BLB and sunshine hours showed positive correlation with disease severity. On the basis of pooled data of both the years, a significantly negative correlation with maximum temperature, minimum temperature, evening relative humidity and rainfall but non-significantly negative correlation with morning relative humidity were observed. The generated model had coefficient of determination (R2) of 0.95, which showed that 95 per cent of the variation in the severity of BLB was influenced by maximum and minimum temperature, maximum and minimum relative humidity and rainfall during 2019 and the same model had coefficient of determination (R2) of 0.94 which showed 94% of the variation in the observed severity of bacterial leaf blight of rice was influenced by maximum and minimum temperature, morning and evening relative humidity, sunshine hours and rainfall during 2020. On the basis of pooled data, model had coefficient of determination (R2) of (0.89) which showed that 89 per cent of the variation in the observed disease severity of BLB was influenced by maximum and minimum temperatures, morning and evening relative humidity, sunshine hours and rain fall.

Keywords

Weather, severity, disease, BLB, rice, blight, parameters

Conclusion

During 2019, the disease severity of 1.03 per cent was recorded in 31st standard meteorological week (SMW) when the crop was at tillering stage and when maximum and minimum temperatures of 32.66 and 26.20ºC, morning and evening relative humidity of 86.00 and 67.71 percent, sunshine of 5.71 hrs and total rainfall of 50.20 mm, was recorded. Terminal severity of BLB was 44.13 per cent when the crop was at harvest stage during 46th SMW, with maximum and minimum temperatures of 24.00 to 13.41oC, morning and evening relative humidity of 89.86 to 61.71 per cent, sunshine hours of 3.54 and total rainfall of 2.80mm. During 2020, the disease severity of 1.47 per cent was recorded in 31st SMW, with maximum and minimum temperatures of 34.6 and 25.7oC, morning and evening relative humidity of 87.0 and 64.6 percent, sunshine hours was 6.4 and total rainfall of 54.6mm. Terminal disease severity was 45.45 per cent when the crop was at harvest stage during 46th SMW, with maximum and minimum temperatures of 3.2 to 9.8oC, morning and evening relative humidity of 92.7 to 58.0 per cent, sunshine hours of 4.3 and total rainfall of 27.8 mm. On the basis of pooled data of the two years, the disease severity of 1.25 per cent was recorded in 31st SMW with maximum and minimum temperatures of 34.60 and 25.97°C, morning and evening relative humidity of 86.50 and 66.14 percent, sunshine hours was 6.05 and total rainfall of 52.40 mm. Terminal disease severity was 44.79 per cent when the crop was at harvest stage during 46th SMW with maximum and minimum temperatures of 23.21 and 11.63°C, morning and evening relative humidity of 91.29 and 59.86 per cent, sunshine hours of 3.90 and total rainfall of 15.30 mm. In 2019, maximum infection rate (r) of 0.18 was observed during 32nd SMW in basmati-370, while during 2020, maximum infection rate (r) of 0.16 was observed during 33rd SMW. On the basis of pooled data, maximum infection rate (r) of 0.12 was observed during 32nd SMW. During 2019 AUDPC was maximum at 46th SMW (293.19) when the disease severity was 44.13 per cent. Similarly during 2020, it was maximum at 46th SMW (305.27) when disease severity was 45.74 per cent. On the basis of pooled data, it was maximum at 46th SMW (299.23) when disease severity was 44.79 per cent. Correlation studies revealed that the relationship between disease severity and weather factors during 2019 had significantly negative correlation with maximum temperature, minimum temperature and evening relative humidity, and non-significant negative correlation with rainfall and sunshine hours, though there was positive but non-significant correlation with morning relative humidity. During 2020, significantly negative correlation with maximum temperature, minimum temperature, evening relative humidity and rainfall, whereas non-significant negative correlation with morning relative humidity was observed, whereas, positive but non-significant correlation was observed with sunshine hours. On the basis of pooled data, significantly negative correlation with maximum temperature, minimum temperature, evening relative humidity and rainfall, and non-significant negative correlation with morning relative humidity was observed, however, there was positive but non-significant correlation with sunshine hours. Multiple linear regression studies revealed that among the weather parameters, maximum temperature and number of rainy days had a significant contribution in the increase in per cent disease severity. For the development of disease, there were 94 and 89 per cent influences of all the six weather factors on cv. Basmati-370 and the remaining 6 and 11 per cent variations were unexplained, during both the years i.e. 2019 and 2020, respectively.

References

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How to cite this article

Tabasia Amin, Vishal Gupta, Aarushi Singh and Sheikh Saima Khushboo (2022). Effect of Weather Parameters on the Severity of Bacterial Leaf Blight of Rice (cv. Basmati-370). Biological Forum – An International Journal, 14(4): 123-133.