Distribution of foliar fungal endophytes of Pinus strobus between and within host trees

Abstract

The distribution of foliar fungal endophytes within and between needles and trees of Pinus strobus L. (white pine) is largely unknown. In this study, needles were collected in Muskoka, Ontario, plated, and scored for hyphal outgrowth of endophytes to observe distributional patterns. Individual trees displayed different levels of infection but branches within those trees had similar levels. There was a large difference in the infection levels between the two extant needle age-classes, with the youngest needles being virtually endophyte-free. Needles divided into four sections exhibited the most hyphal outgrowth from the distal portion and the least from the medial-proximal portion. Cultural morphotypes were primarily of the Lophodermium and Hormonema morphologies. Lophodermium occurred at all positions along the needle but Hormonema was restricted to the proximal and distal portions. Infrequently occurring fungi of diverse morphotypes were found at all four needle positions. A separate experiment compared levels of endophyte infection between Muskoka trees and trees growing in an urban area (Guelph, Ontario). Needle pieces from Guelph hosts had low rates of infection (0.02%) compared with needle pieces from Muskoka hosts (66.5%). Thus, for white pine, foliar endophyte distribution is patchy within and between needles, trees, and locations, possibly reflecting differences in microhabitat or infection success.