Abstract
The development of biotechnologies based on beneficial microorganisms for improving soil fertility and crop yields could help to address many current agriculture challenges, such as food security, climate change, pest control, soil depletion while decreasing the use of chemical fertilizers and pesticides. Plant growth-promoting (PGP) microbes can be used as probiotics in order to increase plant tolerance/resistance to abiotic/biotic stresses and in this context strains belonging to the Pseudomonas chlororaphis group have shown to have potential as PGP candidates. In this study a new P. chlororaphis isolate is reported and tested for (i) in vitro PGP features, (ii) whole-genome sequence analysis, and (iii) its effects on the rhizosphere microbiota composition, plant growth, and different plant genes expression levels in greenhouse experiments. Results showed that P. chlororaphis ST9 is an efficient rice root colonizer which integrates into the plant resident-microbiota and affects the expression of several plant genes. The potential use of this P. chlororaphis strain as a plant probiotic is discussed.
Highlights
The agriculture of the 21st century has several challenges to face
Inoculated plant growth-promoting rhizobacteria (PGPR) must interact or compete with other microorganisms in the rhizosphere microbiome and this can cause the short persistence of the inoculated bacteria possibly affecting its probiotic effects [2]
The plethora of secondary metabolites and antimicrobial activities encoded in its genome and a biocontrol test against D. zeae infection make P. chlororaphis ST9 a potential candidate for biotic stress tolerance tests upon its inoculation
Summary
The agriculture of the 21st century has several challenges to face. Among them are the increase in population and the growing demand for food in the context of climate change, soil depletion, competition between different land uses, and the need to reduce chemical fertilizers and pesticides. The interest in developing PGP probiotic microorganisms has increased intending to reduce chemical fertilization [11] and pesticide use, both in conventional and organic farming, to offer healthier food and improving the sustainability of crop production [12]. P. chlororaphis strains produce different antifungal compounds such as Prn (pyrrolnitrin), PCN (phenazine-1-carboxamide), PCA (phenazine-1-carboxylic acid), 2-OH-PHZ (2-hydroxyphenazine), HPR (2-hexyl-5propyl-alkylresorcinol) and HCN (hydrogen cyanide) These molecules inhibit the growth of various phytopathogens belonging to the Fusarium group [26,27] and different species of Colletotrichum, Phytophthora, Pythium, Sclerotinia, Magnaporthe oryzae [28] and Rhizoctonia [29], protecting plants such as maize [30], tomato [31]. The potential use of this P. chlororaphis strain as a plant probiotic for rice cultivation is discussed
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