Evolutionary biology of microcyclic rust fungi

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This study primarily concerned with the nuclear behavior associated in the metabasidium production in relation to the reduction of the life cycle in the rust fungi. In this study, the types of nuclear behaviors associated in the metabasidium production were newly observed for Puccinia circaeae Pers., P. lantanae W. G. Farlow, P. nipponica Dietel, P. patriniae P. Hennings P. tiarellaecola Hiratsuka, f. and Endophyllum paederiae Stevens & Mendiola. In P. arenariae Winter and P. horiana P. Hennings, the observed mode of the metabasidium production was the same as that has previously been reported. However, the nuclear behavior in the life cycle was different from the previous reports.Among the nuclear behavior types observed in the species, the type found in Puccinia circaeae had not been known for the Uredinales. In this species, karyogamy took place in the teliospore and the subsequent first meiotic division occurred in the metabasidium upon germination of the teliospore. The two haploid nuclei were delimited by a septum and the metabasidium became two-celled. From each of the two cells, a uninucleate basidiospore was formed. The second meiotic division took place in the basidiospore, the spore becoming haploid binucleate.It has been suggested that homothallism often evolves during the life-cycle reduction in the rust fungi. There have been only a few experimental proofs for this possibility. In this study, Kuehneola japonica (Dietel) Dietel and P. lantanae were proven to be homothallic by a single basidiospore inoculation, where the mycelium derived from a single basidiospore produced the telium and the teliospore.