Cross-Pathogenicity of Colletotrichum sp. Isolates from Avocado and Banana Fruits in Côte d’Ivoire

Abstract

Aims: The present study aimed to evaluate the cross-pathogenicity of Colletotrichum isolates obtained from different hosts and production zones using substitute hosts. Study Design: The experimental design followed a completely randomized layout with 19 treatments and five replicates. Place and Duration of Study: The in vitro assay was conducted in the Plant Pathology and Plant Biology Laboratory at the Institut National Polytechnique Félix HOUPHOUET-BOIGNY, Côte d’Ivoire. Methodology: A total of 19 morphological groups of Colletotrichum sp. isolates were selected from a collection of 67 isolates obtained initially from avocado and banana fruits and characterized microscopically. Cross-inoculation assays were conducted on the substitute hosts 'Lula' (Avocado) and 'Grande Naine' (banana). Lesion diameters were measured along two perpendicular axes passing through the center of each lesion. Results: The isolates induced lesions of varying diameters ranging from 2.9 ± 6.5 mm to 24.6 ± 5.2 mm. All 11 Colletotrichum sp. groups isolated from Avocado caused lesions on banana fruits. Conversely, among the eight groups isolated from banana, only three isolates (KB17A, KB37A, and KB06A) produced lesions on avocado fruits. Analysis of variance revealed highly significant differences (P = .001) in lesion diameter among the Colletotrichum isolates at the 5% significance level, allowing for their classification into five homogeneous groups on Avocado and eight on banana. Some lesions were smaller or comparable in size to those observed on the control fruits. Conclusion: These findings demonstrate that several Colletotrichum isolates are capable of cross-infecting different fruit hosts. The identification of both host-specific and polyphagous isolates suggests potential implications for disease epidemiology, highlighting the risk of pathogen spread between adjacent crops. This knowledge is crucial for developing integrated management strategies, such as advising against the intercropping of susceptible hosts and informing targeted fungicide application programs in Côte d’Ivoire.