Assemblages of Endophytic Fungi in Coppice Shoots of Castanea sativa

Abstract

Young healthy coppice shoots of Castanea sativa were collected at two sites, one south and one north of the Alps in Switzerland. The surface-sterilized shoots were incubated under two different drying regimes to isolate endophytic fungi. The frequency of shoots showing emergence of endophytic mycelia was significantly different under the two drying regimes. However, no significant differential effect on the frequency of emergence of any endophyte species was observed. The most frequently isolated fungi were Amphiporthe castanea, Pezicula cinnamomea, Coryneum modonium, and Phomopsis sp. Pezicula cinnamomea occurred more frequently south of and Co. modonium more frequently north of the Alps. Cryphonectria parasitica, the causal agent of chestnut blight, was detected as an endophyte in several shoots from south of the Alps where it constituted a minor component of the endophyte assemblages. All Cr. parasitica isolates were of the normal phenotype and showed a high laccase activity. The results of additional experiments can be summarized as follows: i) endophytes almost exclusively colonized the phellem and were not found in the pith and the xylem and only very rarely in the bark tissues between phellogen and cambium; ii) phellem colonization varied between three and 16 thalli as well as between one and six species per cm2; iii) the density of lenticels and the frequency of colonization of shoots by endophytes were not correlated; however, phellem adjacent to lenticels was more frequently colonized than the lenticels themselves.