Management of Pythium rhizome rot of ginger by surfactant producing rhizobacteria

摘要

Detailed experiments were undertaken on biosurfactant producing rhizobacteria for management of the rhizome rot of ginger. Initially, rhizome rot-affected ginger plants were taken from ginger-growing regions of Tamil Nadu and utilized to isolate the pathogen, which was identified as Pythium aphanidermatum. The culture of Bacillus tequilensis, Pseudomonas koreensis and P. monteilii were received from Horticultural Research Station, Yercaud, India and used in the study to evaluate the same against P. aphanidermatum. The reduction of mycelia growth of P. aphanidermatum was recorded to be maximum in Petri plates with B. tequilensis and which was followed by P. monteilii. In Petri plates containing Siegmund Wagner medium with cetyl triammonium bromide (CTAB) and methylene blue, all the three bacteria expressed halo region and possessed surfactant ability in drop collapse test. B. tequilensis grown in basal salt medium had reduced the surface tension by drop weight as well as drop count method. B. tequilensis had maximum emulsification index value in all hydrocarbon materials used in the study when compared to other bacterial strains. The rhizome treated with B. tequilensis and challenge inoculated with P. aphanidermatum had the maximum height of the ginger plant, lower population of P. aphanidermatum in soil and rhizome rot incidence. The effect of rhizobacteria was assessed under field conditions in two locations against the disease. The rhizome treatment with 0.2 B.tequilensis for 20 minutes and basal application of talc formulation of the B.tequilensis at 2.5 kg/ha at 3, 5, and 7 months after sowing (MAS) demonstrated reduced disease incidence and higher rhizome production than the other rhizobacterial treatments.