Mating Type o f Pine Gall Rust

Craigie reported for the first time the occurrence of heterothallism in a rust fungus, Puccinia helianthi Schwein.,2) and stated that when two basidiospores of opposite sex, "+" and "-", are sown close together on a sunflower leaf so that the pustules arising from the two infections soon coalesce, the two monosporous mycelia come into contact, fuse together, and give rise to normal binucleate aeciospores. Buller reviewed the mating system of heterothallic and long-cycled rust fungi, and showed that there are two normal modes of initiating the sexual process : mode I, by the fusion of a "+" mycelium with a "-" mycelium in a host-leaf, when such mycelia (each derived from a basidiospore) happen to meet and form a compound rust pustule ; mode II, by the fusion of a "+" spermatium with a "-" flexuous hypha, or the fusion of a "-" spermatium with a "+" flexuous hypha, in the nectar of a spermogonium after the nectar of "+" and "-" pustules has been mixed through the agency of insects.') At present, this theory has been generally accepted for the rust mating system. In Cronartium quercuum (Berk.) Miyabe ex Shirai, Nakamura reported that 3 selfed galls infected with the rust fungus did not produce aeciospores, while 5 out of 7 cross-spermatized galls did.4~ On the other hand, Kondo reported that 2 out of 136 selfed galls produced aeciospores, and 32 out of 41 pairs (78%) of reciprocally crossed galls produced aeciospores on both galls in the pair, 3 pairs (7%) formed aeciospores on one gall of the pairs, and 6 pairs (15%) did not produce aeciospores on either of the galls in the pair.3) Nakamura and Kondo therefore assumed that C. quercuum was heterothallic.3>,4) We reported previously that none of the 62 self-spermatized galls produced aeciospores, whereas all of the 12 pairs of reciprocally cross-spermatized galls formed aeciospores on both galls in the pair.6) We confirmed that C. quercuum is heterothallic,6> that each of the galls was derived from the infection with a single basidiospore, and that spermogonia occurring on single galls were haplonts and gametophytes. In the present paper we report for the first time the tetrapolar mating system in the rust fungi. Materials and methods. Galls on trunks of Pinus densiflora Sieb. et Zucc. (Age: 19 to 27 years old) trees infected with Cronartium quercuum that were planted in the University of Tsukuba Forest in Nagano Pref., and galls on trunks of P. densi f lora (Age: 16 to 20 years old) trees infected with the fungus in the Ibaraki Pref ectural Forest in Ibaraki Pref, were used for crossing experiments. We confirmed that all the galls in the University of Tsukuba Forest and the Ibaraki Prefectural Forest produced aeciospores in the spring of 1986 and 1987,