Biological Management of Leaf Blight Disease of an Endangered Medicinal Plant.

Gloriosa superba Linn. (Glory lily) is an endangered medicinal plant belonging to the family Liliaceae. A leaf blight disease caused by the fungus Alternaria alternata was observed in different areas of lower Gangetic plains of West Bengal, India. Pseudomonas aeruginosa strain WS-1 showed both in vitro and in vivo antagonistic activity against the pathogen. In dual culture bioassay as circular and semicircular patterns, the isolate quantitatively inhibits the growth of the pathogen by about 77% and 67%, respectively. In talc-based formulation, the strain has adequate shelf life. Experimental data illustrates about 70% survivability of the population after 180 days of storage at 4°C. Foliar application of a talc based formulation of P. aeruginosa strain WS-1 to field condition revealed that the maximum mean disease index reached 1.17 and 1.06 in 2012 and 2013 respectively, indicating 75% and 78% reduction in disease severity respectively when compared to control. Application of the outcome of this work in the commercial cultivation would benefit the growers by facilitating bioorganic production of this important medicinal plant and finally the consumers will tend to receive a pesticide free natural product.