Plant-Growth Promotion and Biocontrol Properties of Three Streptomyces spp. Isolates to Control Bacterial Rice Pathogens

Abstract

Bacterial Panicle Blight caused by Burkholderia glumae is a major disease of rice, which has dramatically affected rice production around the world in the last years. In this study we describe the assessment of three Streptomyces isolates as biocontrol agents for B. glumae . Additionally, the presence of other plant-growth promoting abilities and their possible beneficial effects upon their inoculation on rice plants was evaluated as an ecological analysis for their future inoculation in rice crops. Two isolates (A20 and 5.1) inhibited growth of virulent B. glumae strains, as well as a wide range of bacterial and fungal species, while a third strain (7.1) showed only antifungal activity. In vitro tests demonstrated the ability of these strains to produce siderophores, Indoleacetic acid (IAA), extracellular enzymes and solubilizing phosphate. Greenhouse experiments with two rice cultivars indicated that Streptomyces A20 is able to colonize rice plants and promote plant growth in both cultivars. Furthermore, an egfp tagged mutant was generated and colonization experiments were performed, indicating that Streptomyces A20 –GFP was strongly associated with root hairs, which may be related to the plant growth promotion observed in the gnotobiotic experiments. In order to characterize the antimicrobial compounds produced by strain A20 bacteria, mass spectrometry analyses were performed. This technique indicated that A20 produced several antimicrobial compounds with sizes below 3 kDa and three of these molecules were identified as Streptotricins D, E and F. These findings indicate the potential of Streptomyces A20 as a biocontrol inoculant to protect rice plants against bacterial diseases.

The variability of bacterial communities in both the endosphere and ectosphere of different niches in Chinese chives (Allium tuberosum)

“…Despite the large number of bacterial phyla described in nature and the multiple factors that affect these communities, the bacterial microbiota of plants is dominated by three major phyla (Proteobacteria, Actinobacteria, and Bacteroidetes) in both the above-and below-ground plant tissues [30,31]. This is also consistent with our research (Fig 4).…”

Persistence of plant-mediated microbial soil legacy effects in soil and inside roots

“…The role of Patescibacteria in plant health is still unclear, but they have been recently found inside the tissues of different plants (28,48). However, Actinobacteria, and especially Streptomycetes, are often detected inside plant roots and can act both as pathogens or beneficials to the plant (49,50). Here, we show that root biomass increased across plant species when the relative abundance of Actinobacteria inside the roots increased.…”

Iron-meditated fungal starvation by lupine rhizosphere-associated and extremotolerant Streptomyces sp. S29 desferrioxamine production

“…8,9 Actinobactera, which are also predominantly soil-associated microbes, have also been explored as biocontrol agents due to their prolific antimicrobial potential. 10 This combined with the fact that extremotolerant microbes have adapted to the harsh conditions and the potential of these adaptations to be translatable to biotechnologies, extremotolerant microbes look to be promising sources as biocontrol agents. 11 In Chile, the wine industry is the main agricultural export, estimated at B$2 billion USD in 2017, 12 thus driving a large research interest around protection of wine-producing grapes against various phytopathogens.…”