Mycology and Plant Pathology Division, Department of Botany, University of Lucknow, Lucknow- 226007 India
Debaryomyces hanseniZopf isolated from the fructoplane of apples were found to be effective as biocontrol agent against rot of papaya caused by Ulocladium. chartarum(Pr.) Simm. The ability of D. hansenii to prevent infection of U. chartarum was lost when the antagonist cells were killed by autoclaving. Cell free culture filtrates of antagonist were unable to prevent disease incidence. Efficacy of sodium bicarbonate, sodium chloride, sodium carbonate (0.25%, 0.5% and 1.0%) and calcium chloride (CaCl2 0.25%, 0.5% and 1.0%) solutions alone or in combination with the application of biocontrol agent Debaryomyces hansenii (106 and 109 CFU ml-1) were simultaneously evaluated for the control of Ulocladium rot of papaya. Fresh cells of biocontrol agent proliferated inside the wounds and their survival was not adversely affected by the presence of residues of calcium chloride salt. Sodium carbonate adversely affected the growth of yeast cells in in-vitro and in-vivo experiments. Sodium bicarbonate and calcium chloride also reduced the percent rot but their integration with biocontrol agent enhanced the activity of antagonist at high levels as compared to the single treatments of salts and D. hansenii. The integration of treatments is a promising approach to control the Ulocladium rot of papaya.