Direct effect of soil conditioner against Rhizoctonia solani, a causal of sheath blight disease in rice
2023
Keawmanee, P. | Rattanakreetakul, C. | Pongpisutta, R. | Khwanrot, T.
Sheath blight disease is a major disease of rice, affecting rice from tillering stage until nearly harvest. The lesions can spread to the flag leaf and leaf sheath, leading to a significant yield reduction. The causal agent is Rhizoctonia solani, which can produce the infecting structure as sclerotium. In sustainable agriculture, using organic matter in soil is encouraged, and soil conditioners are employed to enhance soil quality. Nevertheless, the application of soil conditioners can also influence the growth of pathogenic fungi causing diseases. In this study, the aim to investigate the impact of five soil conditioners as 1) high organic matter content (40-45%, hydrolyzed gelatin) two types, 2) fulvic acid and humic acid,3) a blended of organic matter and lime (15% organic matter), and 4) polyhalite mineral on the growth of R. solani under laboratory conditions. The soil conditioner extracts were used to prepare an agar medium for testing with R. solani mycelium. After three days of incubation, it was observed that polyhalite and the blended of organic matter and lime significantly promoted growth of the fungal pathogen, reflecting the highest mycelium growth with polyhalite treatment and an increasing number of sclerotia in the blend of organic matter and lime after five days of incubation. Both treatments showed larger and thicker cell walls of fungal hyphae compared to the control. Higher organic matter treatment and fulvic acid and humic acid exhibited strong inhibitory effects on fungal growth. Soil conditioners can influence fungal growth and reproductive efficiency of R. solani differently. This information can be used to select an appropriate soil conditioner to manage good practices in fields previously affected by rice sheath blight outbreaks, ultimately contributing to the improvement of crop health and yield.
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