Abstract
The use of beneficial microbes as inoculants able to improve fitness, growth and health of plants also in stress conditions is an attractive low-cost and eco-friendly alternative strategy to harmful chemical inputs. Thirteen potential plant growth-promoting bacteria were isolated from the rhizosphere of wheat plants cultivated under drought stress and nitrogen deficiency. Among these, the two isolates TL8 and TL13 showed multiple plant growth promotion activities as production of indole-3-acetic acid (IAA), siderophores, ammonia, and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase production, the ability to solubilize phosphate as well as exerted antimicrobial activity against plant pathogens as Botrytis spp. and Phytophthora spp. The two selected strains were identified as Kosakonia pseudosacchari by sequencing of 16S rRNA gene. They resulted also tolerant to abiotic stress and were able to efficiently colonize plant roots as observed in vitro assay under fluorescence microscope. Based on the best PGP properties, the strain K. pseudosacchari TL13 was selected to develop a new microbial based formulate. A sustainable and environmentally friendly process for inoculant production was developed using agro-industrial by-products for microbial growth. Moreover, the application of K. pseudosacchari TL13- based formulates in pot experiment improved growth performance of maize plants.
Highlights
According to the Food and Agriculture Organization (FAO), the estimated world population for 2025 will be nearly 8.5 × 109 inhabitants (Timmusk et al, 2017)
A total of 13 bacterial isolates were obtained from the rhizosphere of wheat plants using Augier liquid medium followed by streaking on LG agar medium
Isolates were preliminarily screened for their potential plant growth promoting activities, as indole3-acetic acid (IAA) and siderophores production and ACC-deaminase activity (Table 1)
Summary
According to the Food and Agriculture Organization (FAO), the estimated world population for 2025 will be nearly 8.5 × 109 inhabitants (Timmusk et al, 2017). Among the beneficial microbes employed in agriculture, plant growth-promoting rhizobacteria (PGPR) are the most commonly used These microbes are able by a wide range of mechanisms to improve nutrient availability in soil, plant nutrient uptake and assimilation [i.e., nitrogen fixation, phosphate solubilization, siderophore, indole3-acetic acid (IAA), and ammonia production] and/or providing protection against plant pathogens (Backer et al, 2018; Woo and Pepe, 2018). These microbes could act as biostimulants ameliorating plant growth and crop production in response to abiotic stress in hostile environments (Viscardi et al, 2016; Van Oosten et al, 2017)
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