Screening of Pseudomonas fluorescens isolates for biological control of Macrophomina phaseolina root-rot of safflower

Abstract

The aim of this study was to assess the potential bacterial antagonists to control Macrophomina phaseolinaroot-rot of safflower by using screening methods. In total, 38 fluorescent pseudomonads isolated from rhizosphere soil of healthy safflower plants were collected from major safflower growing areas, 13 were initially selected based on dual culture technique on potato dextrose agar media. Furthermore, these13 isolates were screened for reduction of percent incidence of M. phaseolina and to check their efficacy in seed germination and seedling growth in laboratory condition. Most of the isolates showed varying levels of antagonism againstM. phaseolina in both standard blotter method and paper towel method. In addition, few isolates increased percent germination, root-shoot lengths of safflower. Among them, CTPF31 showed the highest ability to reduce the root-rot disease severity in the greenhouse biological control test. The promised fluorescent pseudomonads (CTPF31 and CTPf36) enhanced the defense enzymes, peroxidase, PAL, β 1,3-glucanase, and chitinase after challenge inoculation with the target pathogen. These results indicated that the dual culture technique and seedling assay are more important for selection of promising biocontrol agents against M. phaseolina, besides they also increased the plant growth by controlling the disease as evidenced by induction of defense enzymes. Key words: Plant growth-promoting Rhizobacteria, safflower, root-rot, Macrophomina phaseolina, Pseudomonas fluorescens, biological control.