Autochthonous Streptomyces regulate the metabolism of seedlings of Araucaria angustifolia (Coniferales) during root colonisation

Abstract

Araucaria angustifolia (Bertol.) Kuntze, known as Brazilian pine, is an endangered species of great ecological and economic importance. This species grows slowly and unevenly, with high mortality in commercial plantations. Streptomyces is a genus of soil microorganisms that may have a beneficial effect on plant growth. This study evaluated the effect of three autochthonous Streptomyces spp. isolates (PM1, PM4 and PM9) on the initial metabolism and development of A. angustifolia seedlings. The enzymatic activity of phenylalanine ammonia-lyase, polyphenol oxidase and peroxidase, and the levels of phenolic compounds, flavonoids and chlorophyll were determined in extracts from roots and leaves of the seedlings. Assays were carried out 1, 3 and 9 days after the roots were inoculated with each isolate. Length and fresh mass of shoots and roots as well as the volume and density of roots were evaluated at 100 days after seedling inoculation. All the Streptomyces spp. showed rhizospheric competence and produced auxin. The activities of polyphenol oxidase and peroxidase exhibited a tissue-temporal regulation in the presence of the isolates. Levels of phenolics, flavonoids and chlorophylls did not change in the period analysed. The root system of seedlings inoculated with all isolates was shorter and denser, with a small volume. The PM9 isolate promoted shoot growth and affected plant metabolism, proving to be a promising rhizobacterium with a plant growth-promoting rhizobacteria role.

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

“…Consequently, the increase in the substrate for ACC oxidase elevates the endogenous concentrations of ethylene [2] and ultimately inhibits root growth. Furthermore, the contact of the rhizobacteria with the developing roots can cause a delay in the initial plant growth due to the deviation in the cellular metabolism to recognize and establish the rhizobacteria-plant interaction, a trade-off often reported in this type of interaction [11,14,45].…”

“…Rouws [4,10]. Strains of Streptomyces species originating from an Araucaria forest were characterized as PGPR, based on their capacity for IAA production [11], phosphate solubilization, antibiosis, and production of siderophores [12]. Some studies have shown a positive effect of Streptomyces spp.…”

Plant Growth-promoting Ability and Pathogen Inhibitory Effect of Actinomycetes Isolated from Fecal Pellets of the Giant Millipede Thyropygus resimus (Diplopoda)

“…As such, Streptomyces strains may enhance the supply of plant nutrients, produce IAA, cytokinins, and siderophores, increase the solubility of phosphate, and control plant pathogens through antibiosis and the production of phenazines. [14][15][16][17][18][19] Horstmann et al 20 isolated Streptomyces sp. from the Fabaceae rhizosphere and tested its plant growth-promoting properties, including siderophore production, 1-aminocyclopropane-1-carboxylate (ACC) deaminase, IAA, and phenazines.…”