Fungal assemblages associated with gall formation by Phytolyma fusca on Milicia excelsa in Nigeria

Abstract. Olorunnibe VN, Omoloye AA, Alabi OY. 2025. Fungal assemblages associated with gall formation by Phytolyma fusca on Milicia excelsa in Nigeria. Cell Biol Dev 9: 91-98. Milicia excelsa is an economically important tropical timber species whose cultivation is frequently constrained by gall formation induced by the iroko gall bug, Phytolyma fusca. Gall development modifies leaf tissues and may create microhabitats that facilitate fungal establishment, yet information on fungi associated with gall systems in M. excelsa under Nigerian nursery conditions remains limited. This study investigated fungal assemblages associated with gall formation by P. fusca on M. excelsa using conventional isolation and morphology-based identification techniques. Samples were collected from healthy leaves, ruptured and unruptured galled leaves, and from nymph and adult stages of P. fusca. Fungal isolation was conducted on potato dextrose agar, followed by purification and identification based on cultural and microscopic characteristics, and fungal occurrence was analyzed descriptively. Four fungal taxa were recovered exclusively from gall-associated tissues and insect stages: Fusarium solani (30%), Fusarium oxysporum (30%), Aspergillus niger (20%), and Colletotrichum coccodes (20%). No fungi were isolated from healthy leaves maintained under protected conditions, and fungal occurrence was restricted to gall-affected tissues and insect stages, with some taxa preferentially associated with ruptured galls. These findings demonstrate that insect-induced gall tissues function as localized microhabitats supporting distinct fungal assemblages, reflecting opportunistic rather than pathogenic colonization of modified plant tissues. This study provides baseline, non-pathogenic evidence of fungal assemblages restricted to P. fusca-induced gall microhabitats in M. excelsa. Further studies incorporating molecular identification and pathogenicity assays are required to clarify the ecological roles of the associated fungi.