As a natural engineer, Plant Growth Promoting Rhizobacteria (PGPR) play an important role in increasing plant growth, yield and enhancing plant tolerance to stressful conditions. These beneficial bacteria take up their position in the rhizosphere, around the plants’ root tissues. They may be in, or on their host tissues and help to provide nutrients to their host plants. For sustainable agriculture, PGPR transmit their extensive assistance in ecosystem management, soil structure maintenance, stress management and plant morphology and physiology modulation in an environmentally friendly manner. Plant- PGPR interactions also stimulate nutrient acquisition and accumulation, improve plant performance and enhance plants’ tolerance to abiotic and biotic stresses. Beside these, PGPR are good biofertilizers and safe for our environment. Nanotechnological advances with PGPR applications are important today to increase the impact of PGPR in agriculture. Undoubtedly, PGPR concept is intimately involved with agriculture, horticulture, forestry and they are too enough to establish a vibrant environment. In this review we have focused on the versatility of PGPR-their performance and aimed to address some future prospects of PGPR as an eco-friendly tool for plant growth regulation.

Endophytes are ubiquitous and grow in plant tissues without causing any harmful effects to the host. They include different groups of microorganisms such as bacteria, fungi and actinomycetes. Along with the host plants, the existing endophytes also co-evolve after a long relationship between them. Host plant-endophyte interaction is similar to that of plant growth promoting microbes as they induce the growth of the host plant and increase resilience against biotic and abiotic stresses. The interaction of plant endophytes at the molecular level and the effect of endophytes on host gene expression is a new field of study and are still rarely explored. Endophytes act as a promising resource of many invaluable bioactive secondary metabolites. Some of these bioactive compounds include alkaloids, polyphenols, sterols, xanthones, terpenoids, flavones, coumarins, polyketides, quinones, saponins, tannins, benzopyrones, dibenzofurans. These secondary metabolites are beneficial for agriculture, industrial and pharmacological purposes. As endophytes have beneficial effects in sustainable agriculture, plant disease management, pharmaceuticals, industry and environmental management in an eco-friendly way, thus improving the strategy of application of endophytes as biological agents in every aspect of our life is a very challenging field of research. Our aim in this present review is to focus on plant-endophyte interactions and their various dimensions in order to address some future possibilities for expediting the bioactive secondary metabolite production.

In the present study, indole-3-acetic acid (IAA) producing plant growth promoting fungus was isolated from rice field of Purba Bardhaman district, West Bengal, India. Among the isolated 6 strains, AP2 (Aspergillus fumigatus) was selected as best-performing plant growth promoting fungal strain as it was an efficient indole-3-acetic acid producer as well as exhibits different plant growth promoting ability viz, phosphate solubilization, siderophore production, ammonia and hydrogen cyanide production etc. Media and different growth conditions (pH, temperature, concentration of sodium chloride) were optimized for augmentation of the indole-3-acetic acid production. The genus of the selected isolate AP2 was identified as Aspergillus fumigatus both by 18S rDNA sequence-based homology and MALDI-TOF analyses of ribosomal protein. Plant growth promoting ability of Aspergillus fumigatus has been confirmed by measuring different morphological and biochemical growth parameters in Trigonella foenum-graecum L. So, AP2 (Aspergillus fumigatus) can be considered as novel plant growth promoting fungal strain that can be applied as bio-inoculants on agricultural field.