Abstract

 Crop-weather based relation and other aspects of aerial blight incited by Rhizoctoniasolani Kuhn were investigated on two mega varieties (JS 335 and JS 97-52, now susceptible) under central Indian conditions during 2017, 2018 and 2019. It was found that aerial severity and sclerotial formation on affected leaves were varied significantly in all three season, and progress of disease was rapid between 63–84 days old crop {full pod (R4) to maturity initiation (R7) stage}.Increasing crop age was also significantly positively correlated with increasing severity (0.732*) and sclerotial formation (0.981**). Mean relative humidity and maximum temperature of current as well as previous week were found to be positively and negatively correlated with increasing severity of aerial blight, respectively. A regression based model with three explanatory variables (Mean RH, Rainfall and Minimum temperature) of current week was found to be most significant in prediction of disease severity (R2=0.946) of aerial blight. Whereas previous week weather variables i.e. rainy days and rainfall were also accounted 71.7 per cent variability (R2 = 0.717) in disease severity. Overall, weekly average maximum temp (27 to 30o C) and mean RH (80 to 90 per cent) in current week coupled with more rainfall and rainy days in previous week were found to be most conducive field condition for rapid progress of aerial blight disease in soybean.
Highlights
IntroductionSoybean Aerial or foliar blight caused by Rhizoctoniasolani Kuhn (teleomorph: Thanatephorus cucumeris (Frank) Donk) is one of the most destructive disease of soybean that causes considerable seed yield loss in many countries including India (Naito et al, 1995; Wan et al, 2005; Williamson et al, 2006; Wratheret al., 2010)
Incidence of Rhizoctonia aerial blight (RAB) was started in first fortnight of August (35-45 days after sowing)in all three year that coincided with the flowering stage (R1 and R2) of crop (Fig. 3)
Whereas sclerotial formation on affected tissue was first noticed after 8-15 days of symptoms appearance and after it progressed rapidly with the age of crop
Summary
Soybean Aerial or foliar blight caused by Rhizoctoniasolani Kuhn (teleomorph: Thanatephorus cucumeris (Frank) Donk) is one of the most destructive disease of soybean that causes considerable seed yield loss in many countries including India (Naito et al, 1995; Wan et al, 2005; Williamson et al, 2006; Wratheret al., 2010). It can be diagnosed by presence of light to dark brown spots, superficial web like mycelium and sclerotia on affected tissue (Verma and Thapliyal, 1976, Sinclair, 1984). The present investigations were undertaken to reveal crop weather relationship and other aspects of aerial blight of soybean that might be useful in minimizing severity by formulating need based effective strategies for central India as well as other part of the country
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