Antibiotic producing endophytic Streptomyces spp. colonize above-ground plant parts and promote shoot growth in multiple healthy and pathogen-challenged cereal crops

Abstract

The Streptomyces spp. used in this work were previously isolated as diazotrophic endophytes from sorghum stems. Here, we characterized the Streptomyces spp. for their colonization ability, plant growth promotion and protection against fungal disease in three cereals. In vitro analysis by dual culture study showed inhibitory effect on the rice pathogen Magnaporthe oryzae B157 along with inhibition of the ubiquitous phytopathogen Rhizoctonia solani by the Streptomyces spp. used in this study. The active compounds responsible for phytopathogen inhibition were extracted with ethyl acetate and tested positive against the fungal pathogens. GC-MS based identification of the active compounds responsible for fungal pathogen inhibition showed them to be 2-(chloromethyl)-2-cyclopropyloxirane, 2, 4- ditert-butylphenol and 1-ethylthio-3-methyl-1, 3-butadiene in extracts of culture supernatants from the three different strains respectively. EGFP tagged Streptomyces strains showed profuse colonization in roots as well as aerial parts of cereal plants. Direct inhibitory action against M. oryzae B157 and R. solani correlated with the observation that upon fungal pathogen challenge, the bacterized rice, sorghum and wheat plants showed significantly good plant growth, particularly in aerial parts as compared to unbacterized controls. In addition, benefit was seen in inoculated healthy plants in terms of increase in wet weight of roots and shoots as compared to the uninoculated controls. The mechanism of biocontrol also involved induction of plant defense response as evidenced by the upregulation of PR10a, NPR1, PAL and LOX2 in Streptomyces colonized plants.

Phylogenetic and Functional Characterization of Culturable Endophytic Actinobacteria Associated With Camellia spp. for Growth Promotion in Commercial Tea Cultivars

“…Beneficial endophytic actinobacteria with potential biocontrol characteristics have been previously isolated from diverse plant species, such as tomato (Passari et al, 2016a), cereal crops (Patel et al, 2018), and legumes (Le et al, 2016;Vijayabharathi et al, 2018). Endophytic actinobacteria augment plant growth directly through nutrient solubilization, modulation of hormone levels, nitrogen fixation (Palaniyandi et al, 2013;Golinska et al, 2015;Figueiredo et al, 2017).…”

Streptomyces sp. CLV45 from Fabaceae rhizosphere benefits growth of soybean plants

“…In recent decades, several studies have demonstrated the potential of plant growth-promoting rhizobacteria (PGPR) for improving crop performance and yield and for controlling pathogen attack [1,6,8]. Among rhizobacteria, Streptomyces have been reported as PGPR, and despite strong interest in the medical field because of their high production of secondary metabolites, few studies have examined this group as biofertilizers or biocontrol agents [12,14,[28][29][30][31][32]. The beneficial effects of these rhizobacteria have been attributed to their ability to produce several compounds including phytohormones, siderophores, antibiotics, and lytic enzymes, as well as to fix atmospheric nitrogen, solubilize phosphate, and induce systemic resistance.…”

Effect of four trace elements on Paenibacillus polymyxa Pp-7250 proliferation, activity and colonization in ginseng

“…However, the mechanism of its action needs to be further studied. The key to the stability of biocontrol bacteria lies in the successful colonization of plant surface, body and plant rhizosphere soil (Patel et al 2018 ; Syed et al 2018 ; Thokchom et al 2017 ). Due to the influence of external environmental conditions, biocontrol bacteria in competition with the soil indigenous microorganisms is not easy to hold a dominant position in the long-term survival and colonization, which greatly affects their actual disease-preventing effect.…”