Isolation and Characterization of Plant Growth Promoting Rhizobacteria Enterobacter hormaechei and their Suppression Efficacy against Colletotrichum falcatum in Combination with Chitosan
Deepmala Katiyar *
Department of Plant Physiology, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India.
A. Hemantaranjan
Department of Plant Physiology, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India.
Bharti Singh
Department of Microbiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India.
Abhishek Kumar Malakar
National Bureau of Fish Genetic Resources, Lucknow, India.
*Author to whom correspondence should be addressed.
Abstract
Aims: This study aimed to explore the suppression efficacy of plant growth promoting rhizobacteria (PGPR) Enterobacter hormaechei, chitosan and its oligomers either singly or in combination on red rot disease causing pathogen Colletotrichum falcatum in sugarcane.
Methodology: The study was conducted to isolate twenty nine bacteria from sugarcane rhizosphere and investigate their potential for plant growth activities. Selected isolate PSC3 was characterized by biochemical and molecular identification by 16S rRNA sequencing. The study was further preceded for in vitro screening of plant growth promoting traits viz., production of Indole-3-acetic acid (IAA), hydrogen cyanide (HCN) ammonia (NH3) production and antifungal activity against C. falcatum.
Results: Among twenty nine isolates strain PSC3 showed highest plant growth promoting traits viz., indole-3-acetic acid, hydrogen cyanide, ammonia production and antifungal activity against C. falcatum among other isolated strains. Nucleotide 16S rRNA sequence analysis using clustalW program revealed that isolate PSC3 showed phylogenetic affiliation and maximum homology (99%) with E. hormaechei. Antifungal activity of chitosan, chitooligosaccharides (COS) and E. hormaechei were checked by inhibition of C. falcatum mycelial radial growth. Among three treatments of chitosan, COS and chitosan + E. hormaechei, two treatments showed significant antifungal activity (P<0.05). Chitosan treatment showed radial growth range from 2.5±0.07 to 1.9±0.03 cm against C. falcatum in comparison with control (9.1±0.09 cm). The significant growth inhibition 79.0% was observed in chitosan at concentration 0.6% but the combination of chitosan with PGPR E. hormaechei PSC3 showed highest growth suppression of C. falcatum (86.8%) whereas fungal treated with only E. hormaechei showed growth radial inhibition 41.3%.
Conclusion: The findings reveal that chitosan and E. hormaechei have significant effect on C. falcatum. This new antifungal combination may be help to prevent red rot disease in sugarcane.
Keywords: Enterobacter hormaechei, Colletotrichum falcatum, sugarcane, chitosan, chitooligosaccharides, antifungal activity.