Evaluation of biocontrol properties of Streptomyces spp. isolates against phytopathogenic fungi Colletotrichum gloeosporioides and Microcyclus ulei

Abstract

South American Leaf Blight (SALB) of the rubber tree, caused by Microcyclus ulei and foliar anthracnose caused by Colletotrichum gloeosporioides, are diseases that adversely affect rubber cultivation in America. Both diseases have a significant economic impact on this agricultural subsector. The aim of the present study was to evaluate the potential as biological control agents of three Streptomyces species strains, namely A20, 7.1 and 5.1, against M. ulei and C. gloeosporioides. The results of analysis of variance (ANOVA) and Tukey post-hoc test of the in vitro antifungal activity assays evidenced the potential of the three Streptomyces strains to inhibit C. gloeosporioides growth through the production of diffusible (A20 and 5.1) and volatile compounds (7.1). Furthermore, other results indicated that strain 5.1 had a high biocontrol activity against C. gloesporoides, and thus such strain was selected for further evaluations as a possible biocontrol agent against M. ulei. In vitro assays suggested that active compounds produced by 5.1 inhibited M. ulei growth by interfering with conidia germ tube and stroma formation. Bioassay-guided fractionation with organic solvents of 5.1 fermentation broths, suggested that antifungal compounds produced by this strain were nonionic compounds of medium-polarity. Currently, studies are ongoing to elucidate the chemical structure of these antifungal compounds. These approaches aim to generate a biological control agent to provide the Colombian rubber subsector with a preventive measure for controlling M. ulei and C. gloeosporioides.

Evaluation of the production of antifungal metabolites against Colletotrichum gloeosporioides in Streptomyces 5.1 by random mutagenesis

“…To confirm Streptomyces 5.1 phenotype as a biocontrol agent against C. gloeosporioides a growth inhibition assay was performed using wildtype strain. The obtained results were compared with Vinchira-Villarraga et al (2017) reports, finding germination inhibition percentages of 59.8 ± 2.3%, which were a non-statistical differential in comparison to 61.1% obtain in previous group research.…”

“…The original wild strain was recovered from a cryopreserved vial, and then grown on ISP3 solid medium (Oatmeal 20 g mL -1 , FeSO 4 .7H 2 O 0,001 mg mL -1 , MnCl 2 .4H 2 O 0,001 mg mL -1 , ZnSO 4 .7H 2 O 0,001 mg mL -1 , Agar 18 g L -1 ). The strain was incubated for 5 days at 30ºC to (i) confirm its macroscopic and microscopic characteristics; (ii) evaluate its antifungal activity against C. gloeosporiodes (as described by Vinchira-Villarraga et al, 2017); and (iii) generate a working inoculum for random mutagenesis (Suárez-Moreno et al, 2019).…”

“…After that, the genotypic characterization was performed by sequencing the Internal Transcribed Spacer 1 using the universal primers ITS1 (5'-TCCGTAGGTGAACCTGCGG-3') and ITS4 (5'-TCCTCCGCTTATTGATATGC-3') (White, Bruns, Lee, & Taylor, 1990). Obtained amplicons were sequenced by duplicate, assembled, and analyzed by BLASTN against GenBank database (Vinchira-Villarraga et al, 2017).…”

“…Their mycelial-like growth allows them to colonize a wide range of ecological niches such as soil, leaves, and rhizosphere of many plants including rice, clovers, soybean, and chickpea (Vurukonda, Giovanardi, & Stefani, 2018). For these reasons, different Streptomyces strains are commonly used as potential biocontrol agents for the management of bacterial, fungal, and oomycetes phytopathogens such as Fusarium spp., Phytophthora spp., and Rhizoctonia spp., as well as several Colletotrichum species (Vinchira-Villarraga et al, 2017;Vurukonda et al, 2018).…”

Evaluasi Cendawan Endofit Asal Tanaman Karet untuk Mengendalikan Colletotrichum gloeosporioides Patogen Penyakit Gugur Daun Colletotrichum

“…Syamsafitri & Hasanudin (2013) telah mengeksplorasi cendawan endofit dari berbagai klon karet dan mendapatkan 13 isolat endofit dari genus Trichoderma, Aspergillus, Penicillium, Gliocladium, dan Pestalotia yang dapat menghambat pertumbuhan C. gloeosporioides. Sementara itu, Villarraga et al (2017)…”