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A study of the dacrymyces deliquescens complex Magasi, Laszlo

Abstract

The main objective of the present study was to determine whether the varieties of Dacrymyces deliquescens sensu Kennedy represent a single species or are three distinct species, and to study the life cycles of the fungi of this complex. An unsuccessful attempt was made to grow these fungi through their life cycles in culture. Cultural characteristics were compared among the varieties as well as to those characteristics reported in the literature. To obtain single spore cultures for mating tests, eight methods and six media were tried without successful results. Of the 1560 spores isolated only three resulted in mycelial growth. Erroneous isolation and the presence of a number of spores were suspected in these cultures. The development of the basidium and of basidiospores were studied cytologically to determine the fate of the two nuclei remaining in the basidium. The two supernumerary, nuclei remain in the hypobasidium and degenerate. Conidia produced on the mycelium are globose, elliptical or oval for D. deliquescens (Merat) Duby var. deliquescens Kennedy, D. deliquescens var.ellisii (Coker) Kennedy and D. deliquescens var. minor (Peck) Kennedy respectively. It is suggested that these conidia are carried away by water rather than ejected by some mechanism, as has been previously proposed. Color differences among cultures and different shape of conidia produced indicate a definite degree of separation while intermediate forms among the three organisms indicate close relationship. Whether there are three species or one species with three varieties involved cannot be determined without mating tests. The suggested life cycle for D. deliquescens var. deliquescens follows: Basidiospores are uninucleate at the time of discharge. The nucleus soon divides and 3-septate, four-celled spores are formed. Germination is induced by a volatile substance which is produced in minute quantities. Cells of basidiospores act independently after germination of the spore. Spores germinate by germ tubes, by conidia or by a combination of the two. Production of conidia terminates the germination of individual cells. The maximum number of germ tubes produced by any one cell is two. Monokaryotic mycelium is produced upon germination of basidiospores and conidia. Dlkaryotization takes place in an unknown way. Arthrospores may be produced on dikaryotic mycelium, and these germinate to produce dikaryotic mycelium. Basidia are formed on dikaryotic mycelium. The young basidium is cylindric, binucleate, and separated from the hyphae by a basal septum. A fusion nucleus is produced which gives rise upon division to four stichobasidially arranged daughter nuclei. One nucleus passes into each epibasidium and this later becomes the nucleus of the spore. Two nuclei remain in the hypobasidium and degenerate.

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