AM fungi shields Coleus forskohlii from root rot incidence

Abstract: This study was taken up to determine the combined effect of arbuscular mycorrhizal (AM) fungi and plant growth promoting rhizobacteria (PGPR) in controlling root rot caused by Macrophomina phaseolina in Coleus forskohlii. AM root colonization was up to 70-73 per cent under combined inoculation of Scutellospora sp + Pseudomonasfluorescens + Trichoderma viride and 44-45 per cent under individual inoculation. A correlation analysis indicated that more the AM root colonization (73 per cent) less the root rot (28 per cent) incidence. The activity of the defense enzymes viz., peroxidase, polyphenol oxidase and superoxide dismutase was found to be high at 30 days after inoculation of the pathogen in the co-inoculated treatments. Another correlation study between AM colonization and enzyme activity, showed low root rot index. There was a loss in the alkaloid content due to pathogen infection, yet, the combined treatments recorded a threefold increase in disease suppression.