Investigation of Rhizoctonia Aerial Blight in Soybean: Onset, Progression and Sclerotia Development

Abstract

Soybean crops worldwide can be affected by numerous harmful plant pathogens. Aerial blight caused by Rhizoctonia solani Kuhn is a severe disease that affects soybean production worldwide. Incessant soybean cultivation and other factors have led to an upsurge in the incidence of aerial blight in major soybean-growing regions of India. In the present investigation, various aspects of aerial blight, i.e., initiation timing, rapid progression phase, and development of survival structures, were studied in a field trial on 10 different soybean genotypes at J.N.K.V.V., Jabalpur, during Kharif 2022. The per cent disease index and sclerotia per trifoliate leaves were recorded at regular intervals. The symptoms of aerial blight started from 50.5 to 68.0 days after sowing. The highest aerial blight severity was noticed in JS 20-29 (29.2%). Aerial blight progression was rapid during late reproductive stages (R5 and R6) (September 10 to 23) that coincided with the moderate range of weekly maximum temp (29.8 - 30.50C), minimum temp (23.6 - 24.20C), morning Rh (90.6 - 92.4 %), evening Rh (79.0 - 79.4 %) and rainfall (39.3 - 118.0 mm) at experimental location. After 21 days of symptoms, sclerotia development was noticed in all the varieties, ranging from scattered (>10- 25/trifoliate leaf) to high (≥50 sclerotia/ trifoliate leaf). The study indicated that high sclerotia were formed in all varieties affected by aerial blight at a later stage of disease development. These sclerotia may be crucial for initiating disease in other host crops or in soybeans next season. This study may also facilitate the suitable implementation of management strategies to decrease disease severity of aerial blight in central Indian conditions.