Anthracnose of grapevines in Sri Lanka: Pathogen identification, epidemiological insights, and in vitro evaluation of bioactive extracts

Abstract

Anthracnose disease of grapevines, historically attributed to Elsinoe ampelina, has emerged as a significant concern in the Jaffna Peninsula, Sri Lanka. This study aimed to characterize the disease’s etiology, epidemiology, and potential for biological control. Field assessments over two cultivation seasons (2022–2023) revealed a consistent pattern of disease progression, with peak incidence and severity occurring between 40 and 60 days post-pruning. Rainfall positively correlated with disease metrics, while wind speed showed a suppressive effect. Morphological and cultural characterization of 54 fungal isolates, coupled with multilocus phylogenetic analysis (ITS, actin, and histone H3), confirmed the presence of two distinct Colletotrichum morphotypes within the C. gloeosporioides species complex, potentially representing a novel lineage. Pathogenicity assays verified the virulence of representative isolates on grape leaves and fruits under both in vitro and in planta conditions. Furthermore, spore germination and lesion development were significantly inhibited by cell-free suspensions from Pseudomonas fluorescens, Bacillus megaterium, and ethanol extracts of Azadirachta indica, Lantana camara, Vitex negundo, Stoechospermum marginatum, and Padina boryana. These findings establish a members of new lineage of C. gloeosporioides complex as the primary causal agent of grape anthracnose in the region and highlight the promise of integrating biocontrol agents and botanical extracts into sustainable disease management programs.