Sargassum tenerrimum extract reduces Sclerotium rolfsii stem rot disease in peanut by modulating physio-biochemical responses

Peanut stem rot disease, caused by the necrotrophic soil-borne fungus Sclerotium rolfsii, has a significant negative impact on crop yields. Chemical fungicides can mitigate the loss incurred by fungus, however, their usage raises environmental and human health concern. Seaweeds extracts are getting importance as bio-stimulant for improving growth and disease resistance in different plants. In the present study, we investigated the potential of Sargassum tenerrimum extract (S-extract) in controlling stem rot disease in peanuts. The foliar application of S-extract was applied at vegetative and reproductive stages on peanut plants to study plant growth and reduction of S. rolfsii-induced disease. Plant height, number of branches and branch length increased in S-extract treated plants (S) as compared to S-extract + S. rolfsii treated plants (S + F). Similarly, the activity of anti-oxidative enzymes such as catalase (CAT), guaiacol peroxidase (GPOX), polyphenol oxidase (PPO), and superoxide dismutase (SOD) increased by application of S-extract. Pigments such as chlorophyll a, chlorophyll b, and carotenoids showed higher accumulation in S-extract treated plants. The increased membrane stability index and reduced electrolyte leakage in S and S + F plants, positively affected the health and biotic stress tolerance of the plants. S-extract reduced the reactive oxygen species (ROS) such as O₂^•− and H₂O₂. Total phenol, soluble sugars and total amino acid accumulation were higher in S and S + F plants compared to C and F at vegetative stage. The mitigation of disease can be attributed to the application of S-extract leading to the elevated activity of antioxidant enzymes and the accumulation of non-enzymatic antioxidants, osmolytes, and pigments. Therefore, S-extract represents an environmentally friendly resource that can be employed in sustainable agriculture practices to boost plant growth and enhance disease tolerance.