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First record of Melampsoridium hiratsukanum on alder in Norway

2004; Wiley; Volume: 53; Issue: 4 Linguagem: Inglês

10.1111/j.1365-3059.2004.01032.x

1365-3059

H. B. Gjærum, Kåre Arnstein Lye, Halvor Solheim,

Plant Pathogens and Resistance

In September 2001, the uredinia sori of a rust were found on alder trees (Alnus incana) in Ås parish, Akershus, in south-eastern Norway. Further examination of these sori, which always occurred on the lower side of the infected leaves, revealed urediniospores measuring 25–31 × 12–14 µm, which were uniformly echinulate and which had apical spines. From this morphology, Melampsoridium hiratsukanum was identified (culture reference Lye no. 25356). Melampsoridium betulinum is also known to occur on A. glutinosa in Ås (Roll-Hansen & Roll-Hansen, 1981). A germination test with fresh urediniospores of M. hiratsukanum revealed four to six bizonate pores, similar to those reported for M. betulinum. However, this rust lacks spines in the apical region of its urediniospores and it is the presence of spines in the apical region that distinguishes these rust species (Kaneko & Hiratsuka, 1981). Melampsoridium alni, an Asian rust of Alnus spp., was also ruled out as it, too, lacks spines at the apical region of the urediniospores and has only two germ pores, one at each end (Kaneko & Hiratsuka, 1981). Melampsoridium hiratsukanum often causes considerable damage to foliage, which can easily be seen from a distance. Leaves turn either greyish-green or a golden colour, and the margins curl inwards. Sometimes leaves may drop prematurely, but to a much lesser extent than experienced with M. betulinum on Betula spp. Melampsoridium hiratsukanum does not attack alder until late summer or early autumn, with severe attacks occurring mainly in September and October. The long-term effects of the rust on the host are therefore less severe. During 2002 and 2003, Alnus species were examined for rusts throughout much of Norway and M. hiratsukanum was found on A. incana at about 400 localities, from sea level to 870 m above sea level. The rust was also found on A. glutinosa, at eight locations. It was not found on A. viridis, a rare alder, recently introduced to Norway. So far, the northern limit of M. hiratsukanum in Norway is at 66° north (Luktvasslimo in Vefsn parish in Nordland county). The species was also common in Sweden, in areas near the Norwegian border. Melampsoridium hiratsukanum was first described on Alnus hirsuta from Hokkaido in Japan in 1927. It has now become well established in Europe, being first noted in Estonia in 1996 and in Finland in 1997 (Kurkela et al., 1999). Other recent new records include Hungary (Szabo, 2002) and Poland (Piatek et al., 2001). This is the first record for this disease in Norway.