Gymnosporangium sabinae found in Norway

In October 2005, leaves of a cultivated pear tree (Pyrus x communis) heavily infected with a rust fungus were collected in a private garden in Kristiansand (58° 10' N, 8° 03'E). On the upper side of the leaves there were irregular, pale brown spots with orange-red spermogonia, type 4 (Fig. 1). In light swellings on the lower side there were horn-like aecia (Roestelia-type) in small groups (Fig. 2). The attack was followed by early fruit drop. These symptoms had been observed for at least the ten last years, but were previously restricted to few leaves only.

In May 2006, swellings on twigs of Juniperus chinensis (Fig. 3) were found very close (1 - 1.5 m) to the pear tree that had severely infected leaves in 2005. On the swellings we found teliospores of Gymnosporangium sabinae (Dickson) G. Winter (syn. G. fuscum DC.). G. sabinae alternates between the hosts of pears and Juniperus species. J. sabina L. and J. virginiana L. are also hosts for this rust species.

The aeciospores measured 24 - 29 (- 32) x 20 - 24 µm and they were subgloboid, ellipsoid or somewhat irregular with 6 - 8 germpores. The teliospores measured 40 - 53 (- 61) x 15 - 24 µm and they were ellipsoid, rounded at both ends or somewhat attenuate. Furthermore, they were slightly constricted at the septum, with walls 1 µm thick, hyaline or tinted. Some spores were more obovoid with brown walls (Fig. 4), up to 3 µm thick near the septum. The walls were smooth with two germpores in each cell near the septum. Pedicels were long, thin-walled and hyaline. Our findings correspond well to the description given by Gäumann (1959).

G. sabinae is reported from many countries in Europe, and also from Asia, Africa, and North America (CMI 1989). In this CMI distribution map occurrence in Norway is given by a reference to Bernaux (1956), but in Bernaux's publication we do not find that Norway is mentioned at all. The mistake might be due to confusion with a reference by Bernaux (1956) to a paper by the Norwegian mycologist Jørstad (1943), where he dealt with Cyprian rusts, among them also the species in question. Thus, this species is new to the rust flora of Norway. The many specimens of J. chinensis, as well as other exotic Juniperus species planted in the neighbourhood of the infected pear tree, were possible vectors from foreign nurseries.