2.2.27
SOMATIC INCOMPATIBILITY TEST OF ARMILLARIA MELLEA SUBSP. NIPPONICA FROM JAPAN

K TERASHIMA1, JY Cha2 and K MIURA1

1 Department of Forest Science, Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan; 2 Experiment Forest, Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan

Background and objectives
Armillaria mellea (Vahl: Fr.) Kummer sensu lato is an important fungus which causes Armillaria root and butt rot in forests and has a world-wide distribution. In Armillaria species with a heterothallic life cycle, the somatic incompatibility test is useful for identification of the individual mycelium (genet), and has been used to map genets in the field. Abomo-Ndongo and Guillaumin [1] have indicated, in African Armillaria isolates with a homothallic life cycle, that the somatic incompatibility test is useful for grouping in intraspecies and interspecies.

Cha and Igarashi [2] reported A. mellea subsp. nipponica with a homothallic life cycle, and its life cycle was different from that of A. mellea sensu stricto from North America and Europe [2]. However, it is unknown whether the life cycle of A. mellea subsp. nipponica is a secondary homothallism. The knowledge of somatic incompatibility in A. mellea subsp. nipponica is necessary for the study of its life cycle, population structure and taxonomy. In this study, we examine the somatic incompatibility among diploid progeny, and between isolates collected at different locations.

Materials and methods
The parental isolates HUA93110 and HUA94135 from the tissue in the basidiome, which were collected at different locations more than 10 km apart, and their diploid progeny from the basidiospores were used in somatic incompatibility test. Pairings among the isolates were placed on Shaw and Roth medium (4% malt extract, 2% dextrose, 0.5% bacto-peptone, 1.9% agarose) in a 9 cm Petri dish and were incubated at 25°C for 2-3 weeks. Three replicates were prepared for each pairing.

Results and conclusions
Pairings between the parental isolates and their progeny, and pairings among the progeny were compatible in all 78 combinations of pairings from each of the HUA93110 and HUA94135 isolates. Furthermore, pairings between the parental isolates HUA 93110 and HUA94135 showed a compatible reaction. In Armillaria species with a heterothallic life cycle, pairings among synthetic diploid progeny were 56% compatible in A. luteobubalina Watling and Kile, and 48% in A. borealis Marxmöller and Korhonen. In A. mellea subsp. nipponica with a homothallic life cycle, pairings among progeny showed a 100% compatible reaction, as observed in African A. mellea with a homothallic life cycle. There are two possibilities for this result: (1) all the isolates examined in this study have an identical genotype, or (2) the genotypes of the isolates are different, but for unknown reasons, they cannot recognize each other, or they can but they do not show incompatibility among themselves.

Reference
1. Abomo-Ndongo S, Guillaumin JJ, 1997. European Journal of Forest Pathology 27, 201-206.
2. Cha JY, Igarashi T, 1995. Mycoscience 36, 143-146