Endophytic fungi associated with healthy pine needles and needles infested by the pine needle gall midge, Thecodiplosis japonensis

Abstract

The endophytic mycobiota of the galls of pine needle gall midge, Thecodiplosis japonensis, and healthy current-year needles of Pinus densiflora and the F₂ hybrid pine (Pinus thunbergii × (P. thunbergii × P. densiflora)) was compared. Phialocephala sp. was the dominant endophyte isolated from the galls and from the basal regions of healthy needles. Species richness in endophytes was facilitated in galls compared to the basal region of healthy needles, and the commencement of their colonization was hastened in galls. In the early stages of gall formation, however, no endophyte was isolated, suggesting that gall endophytes are not carried into the galls by the midge. Endophytes of healthy and galled pine needles were divided into two groups: position-specific fungi, which showed intrinsically restricted distributions on needles; and gall-specific fungi. These two groups might represent different ecological groups of endophytes. Possible interactions between endophytes and the pine needle gall midge are also discussed. Key words: endophytic fungi, Pinus densiflora, F₂ hybrid pine, pine needle gall midge.