In Vitro Evaluation of Sea Weed Extracts and Bio-control Agent against Rhizoctonia solani causing Rice Sheath Blight Disease

Rice (Oryza sativa L.) is an important staple food crop for majority of the world. Many biotic stresses hamper rice production and specifically, fungal diseases cause huge economic losses. Among different fungal disease of rice sheath blight caused by Rhizoctoniasolani Kuhn is emerging as a very destructive disease and it is an important one responsible for losses in grain yield. Diseases management is currently focused on extensive use of fungicides which has created concerns about environmental pollution, pathogen résistance and escalating costs. The present study focused on the effect of various seaweeds extracts and biocontrol agents on controlling sheath blight in rice caused by R.solani under in vitro condition. Use of biocontrol agents and sea weed extracts is an eco friendly, cost effective and sustainable alternative method in disease management. Ten isolates of Pseudomonas fluorescens obtained from rice rhizosphere were tested against R. solani. Among these isolates Pf- 5 was effectively inhibited the mycelial growth in dual culture tests was recorded 75.84, mycelial dry weight was recorded 146.00 mg/50ml/broth, minimum mycelial growth was recorded 12.54 mm at 20 % conc. and maximum germination percentage, Shoot and root length, Plant vigour index was recorded 97.21, 9.12 and 18.23 cm, 2658.69. It was followed by the Pf- 3 isolate. Seven different sea weeds such as Sargassum wightii, Padinatetrastromatica, Gracillariacorticata, Chondrococcushornemanii, Ulvalactuca, Enteromorphaintensalis, Enteromorphacompressa were tested against R.solani was carried out by Poisoned food technique, Paper disc and Agar well method . Among the extracts, Sargassumwightii at the highest concentration (20%) was found to be minimum mycelial growth was recorded 12.66 mm and maximum reduction was recorded 42.58 and 43.29mm.