Birch family and environmental conditions affect endophytic fungi in leaves

We investigated whether variation in foliar endophyte frequency among mount ain birch trees from different maternal families was due in part to genetic differences among trees. The effect of different environmental conditions on the susceptibility of these mountain birch families to foliar endophytes was tested. The 3-year study was conducted in two tree gardens (altitudina l difference 180 m) with ten families of mountain birch. The frequency of t he commonest endophytic fungus in mountain birch leaves, Fusicladium sp., w as significantly affected by mountain birch family, with the ranking of fam ilies relative to Fusicladium sp. frequency being consistent from environme nt to environment. Variation in the frequency of Melanconium sp. was diffic ult to interpret because of significant family x garden x year interaction. Fusicladium sp. and Melanconium sp. endophytes were most frequent in diffe rent tree individuals, families and gardens. We conclude that mountain birc h trees show heritable variation in their foliar endophyte frequency, and t hus one of the conditions necessary for foliar endophytes of mountain birch trees to be able to affect the evolution of their host plant is fulfilled. However, the effect of mountain birch family on the frequency of endophyti c fungi varies depending on the endophytic genera in question and partially also on environmental conditions.