Development and seasonal variations of Lophodermium populations on Pinus thunbergii needle litter

A quantitative method was developed to describe Lophodermium (Rhytismataceae, Ascomycetes) populations on Pinus thunbergii needle litter, and seasonal patterns of population variation were examined based on this method. We focused on the formation of black zone lines across needles and the production of Lophodermium ascocarps on needle portions delimitated by zone lines. The study was carried out at a soil erosion control site on a mountain slope and at a coastal sand dune site. Most Lophodermium spp. on needle litter were identified as L. pinastri according to morphological characteristics of ascocarps and ascospores and DNA analysis. Zone lines were produced on needles when isolates of L. pinastri were in contact with other isolates of L. pinastri or with isolates of other species in dual culture tests. This observation provided a rationale to consider that individual colonies with ascocarps and delimitated by zone lines were occupied by a single Lophodermium isolate. Frequency of occurrence of Lophodermium colonies, total colony length, and mean colony number per needle were higher at the coastal sand dune site than at the soil erosion control site. Total colony length and mean colony number also varied with season. Mean colony length and mean ascocarp number per colony were not different between sites or seasons.