Pathogenicity Evaluation of Lasiodiplodia spp. as the Causal Agent of Cashew Gummosis (Anacardium occidentale L.) in Côte d’Ivoire

Cashew gummosis is an emerging phytopathological threat showing an expanding distribution across Côte dʹIvoire. Elucidating the primary etiological agent is a critical prerequisite for developing targeted disease management strategies. To this end, a total of 105 fungal isolates comprising the genera Lasiodiplodia, Pestalotia, and Ceratocystis, which were recovered from symptomatic gummosis lesions were evaluated.Two distinct inoculation protocols were used: mechanically wounded and non-wounded cortical tissue applications. The bioassays showed that macroscopic symptoms developed exclusively following the wounded inoculation protocol, confirming that structural tissue compromise was necessary for fungal entry. Furthermore, symptoms typical of gummosis were confined to seedlings inoculated with Lasiodiplodia isolates. Successful re-isolation of the fungus from newly induced lesions satisfied Koch’s postulates, confirming that this genus is the causative agent of cashew gummosis in Côte dʹIvoire. Agglomerative hierarchical cluster analysis based on virulence parameters categorized the pathogenic Lasiodiplodia population into three distinct phenotypic clusters. Consequently, this study establishes Lasiodiplodia spp. as the principal pathotype driving cashew gummosis in Côte dʹIvoire and highlights intrageneric pathogenic diversity within the genus.