Studien zur Lebensgeschichte des Rostpilzes Gymnosporangium sabinae

Abstract

Ruske, E.; Dörfelt, H.: Studies on the life cycle of the rust fungus Gymnosporangium sabinae. – HercyniaN. F. 43 (2010): 277–298.Gymnosporangium sabinae is a heteroecious rust fungus of economic importance, which can cause seriousdamages on pear-trees. Its life cycle was already clarified in the 19th century. In Europe, Juniperussabina is the main host for the dikaryont and Pyrus communis for the haplont. The host plants and thefungus are not autochthonous in Central Europe. Juniperus sabina is a widespread ornamental shrub andmedical plant, and Pyrus communis is a popular fruit-tree.The telia, which are conspicuous when mature, contain thick-walled as well as thin-walled teliospores.The thick-walled teliospores germinate with basidia, the thin-walled ones often with hyphae. In rarecases undivided teliospores may germinate with hyphae before the development of the transverse septa.Caryological examinations show that the germination occurs after karyogamy and meiosis in each cell ofteliospores. The teliospores that germinate with hyphae are imbedded in a gelatinous mass generated bythe gelatinising pedicels of the teliospores, and they are able to develop mycelia in this gelatinous mass.This mass forms mucous drops falling down from the infected twigs of the dikaryont host which oftenreach, in this way, twigs of lower levels. It is assumed that the germinating hyphae of such teliosporesare able to reinfect the dikaryont host after somatogamic dikaryotisation.The basidiospores germinate with hyphae or repetitively with secondary spores.Key words: Basidiomycota, Uredinomycetes, Pucciniales, Gymnosporangium, life cycle, karyogamy,germination of teliospores, germination by repetition