Exploring Streptomyces albofaciens for the Sustainable Management of Mango Anthracnose

Abstract

Background: Mango (Mangifera indica L.), a commercially significant climacteric fruit, is highly susceptible to anthracnose incited by Colletotrichum gloeosporioides. In pursuit of sustainable alternatives to chemical fungicides, the present study involved the isolation and characterization of native actinomycetes, particularly Streptomyces spp., from mango rhizosphere soils across Tamil Nadu and Puducherry. Ten isolates (AUSA1-AUSA10) were morphologically and microscopically characterized, with AUSA3 exhibiting the highest antagonistic activity against C. gloeosporioides in dual culture assays, recording 79.72% mycelial inhibition. Scanning Electron Microscopy revealed smooth, rod-shaped spores, while molecular identification through 16S rRNA gene sequencing confirmed AUSA3 as Streptomyces albofaciens with 100% similarity. These findings suggest that native S. albofaciens exhibits strong potential as an eco-friendly biocontrol agent against mango anthracnose. Aims: To isolate, characterize, and evaluate native Streptomyces spp. from mango rhizosphere soils for their antagonistic potential against Colletotrichum gloeosporioides, the causal agent of mango anthracnose. Study Design:  Experimental study involving in vitro and molecular evaluation of actinomycete isolates. Place and Duration of Study: Department of Plant Pathology, Faculty of Agriculture, Annamalai University, Tamil Nadu, and Rice Research Station, Ambasamudram, Tamil Nadu, conducted between July 2023 and May 2024 Methodology: Ten actinomycete isolates (AUSA1-AUSA10) were obtained using the soil dilution plate method on Actinomycetes Isolation Agar from mango rhizosphere soils of Tamil Nadu and Puducherry. Isolates were morphologically characterized by macroscopic and microscopic features. Antagonistic activity against C. gloeosporioides was evaluated through dual culture assays on PDA. The most effective isolate, AUSA3, was further characterized using Scanning Electron Microscopy and molecularly identified via 16S rRNA gene sequencing. DNA was extracted using phenol: chloroform: isoamyl alcohol protocol, and PCR amplification was performed with universal primers (27F and 1492R). Results: Among the isolates, AUSA3 exhibited the highest mycelial growth inhibition (79.72%) of C. gloeosporioides, followed by AUSA7 (76.36%). Morphologically, AUSA3 displayed a bright yellow substrate mycelium, powdery surface, and rod-shaped smooth spores. SEM analysis confirmed its spore structure. Molecular identification revealed 100% sequence similarity to Streptomyces albofaciens, and the sequence was submitted to GenBank (Accession No. PV603281). Conclusion: The study confirms that native Streptomyces albofaciens (AUSA3) possesses strong in vitro antagonistic activity against C. gloeosporioides and holds promise as a sustainable biocontrol agent for mango anthracnose management. Its deployment could reduce dependence on synthetic fungicides and promote eco-friendly disease control strategies in mango cultivation.