Formulations of Bacillus Spp. and Pseudomonas Fluorescens for Biocontrol of Cantaloupe Root Rot Caused by Fusarium Solani

Abstract

Abstract The aim of this study was to evaluate the different carrier formulations of antagonistic bacteria on incidence of root rot disease of cantaloupe. Twenty-seven isolates of bacteria isolated from rizosphere cantaloupe plants (collected from different localities of the Assiut Governorate, Egypt) were tested in vitro against the growth of Fusarium solani. The tested isolates exhibited varied percentages of mycelial inhibition of F. solani. The highly antagonistic bacteria isolates were identified as Bacillus subtilis, Bacillus cereus, and Pseudomonas fluorescens. The effect of talc based powder and wood flour as various carrier formulations of antagonistic bacteria were tested on incidence of cantaloupe root rot disease in greenhouse and field experiments. All tested carrier formulations of antagonistic bacteria significantly decreased the disease index percentage (p > 0.05) of root rot disease compared with the control, in greenhouse or in field experiments. Application of the wood flour formulation to the infested soil at the time of planting, gave the lowest disease (21.75%) index percentage compared to an application fifteen days before planting (26.83%). The reverse effect occurred in the case of the talc based powder formulation application. In field experiments, during the two growing seasons of 2009 and 2010, wood flour formulation gave the same effect in the reduction of the disease index when added before planting or at the time of planting to soil infested with the pathogen. However, application of the talc formulation at the time of planting showed the least disease index compared to when it was applied fifteen days before planting. In general, wood flour formulation significantly decreased the disease index when compared with the talc formulation. In all the formulations, a number of viable colonies of bioagents were decreased gradually by prolonging the storage time at 4°C. Storage time was prolonged up to five months. But in the case of B. subtilis on talc and B. cereus on wood flour formulations, storage time needed to be prolonged up to seven months