Plant Growth-Promoting Microorganisms and Their Role in Crop Protection

Abstract

The current study examined the plant growth-promoting microorganisms (PGPMs) to boost plant growth and resistance against common pathogens under controlled conditions in greenhouse. A pot experiment was done with healthy, surface sterilized seeds of maize (Zea mays L.) and inoculated with different strains of Bacillus, Pseudomonas and Azospirillum bacteria separately. The experiment was designed in completely random design (CRD) having four treatments replicated four times with non-inoculated control. Plants were grown under identical water and nutrient conditions, and plant height, roots length, number of leaves, fresh and dry mass and chlorophyll contents were measured at different growth stages. The incidence and severity of disease were measured after pathogen exposure and rhizosphere microbial colonization was determined by using the standard dilution plate count technique. The data were analysed by analysis of variance (ANOVA) and means was separated by Duncan's Multiple Range Test (DMRT) at 5% level of probability. The all three PGPM showed significant (p < 0.05) increase in plant height, root length, number of leaves, biomass accumulation and chlorophyll content compared to the control and the plants inoculated with Bacillus recorded higher values than the plants inoculated with Pseudomonas and Azospirillum. Disease incidence and severity were also significantly reduced in all inoculated treatments relative to the control and rhizosphere colonization was greatest when the plants were inoculated with Bacillus and Pseudomonas. The results are in line with previous studies which established that PGPMs also promote vegetative growth and provide protection against pathogen infection, making them a possibility to be used as environmentally friendly alternatives to chemical fertilizers and pesticides for integrated crop management.