In-vitro Management of Anthracnose of Onion Caused by Colletotrichum gloeosporioides using Plant Extracts and Fungicides

Abstract

Anthracnose disease caused by Colletotrichum gloeosporioides is a significant threat to onion cultivation, leading to considerable yield losses worldwide. In this study, we conducted a comprehensive investigation aiming to understand the prevalence, identification, and management of anthracnose disease in onion crop within District Tando Allahyar, Pakistan. The field surveys were conducted to assess the prevalence of anthracnose across various locations, revealing spatial variability in disease incidence with Jaffar Khan Jamali exhibiting the highest (38%) and Ditto Kalro the lowest (23%). Isolation and identification confirmed C. gloeosporioides as the predominant pathogen causing anthracnose. Pathogenicity tests on Nasarpuri variety confirmed its virulence. Samples exhibiting anthracnose symptoms were collected and processed for isolation and identification of the causal agent. Colletotrichum gloeosporioides was identified as the predominant pathogen responsible for anthracnose infection through morphological and microscopic analyses. Pathogenicity tests confirmed the virulence of C. gloeosporioides on susceptible onion varieties. In vitro evaluations assessed the efficacy of botanical extracts and fungicides against C. gloeosporioides. The study investigated the impact of various botanical extracts on the mycelial colony growth of Colletotrichum gloeosporioides under in-vitro conditions. The control group maintained consistent growth, while the extract from Black Pepper (Piper nigrum) significantly inhibited fungal growth across all doses. Cinnamon (Cinnamomum verum) extract demonstrated a dose-dependent inhibition, with the highest dose resulting in the smallest colony growth, reducing it to 3.1 cm. Following the botanical extracts, the study also assessed the effects of various fungicides on mycelial colony growth in Colletotrichum spp. at different doses. The control group again showed consistent growth, while Argyl Super demonstrated dose-dependent inhibition, with the highest dose reducing colony growth to 4.33 cm. In vitro evaluations showed that black pepper, cinnamon, AKK, and neem extracts inhibited fungal growth, suggesting their potential as alternative management strategies. Fungicides like Argyl Super, Ellectus Ultra, Romeo, and Antracol also showed significant antifungal activity against C. gloeosporioides. The study underscores the potential of botanical extracts and fungicides as integrated disease management tools, contributing to sustainable onion cultivation and mitigating anthracnose-associated yield losses.