The behaviour in soil of spores of four species of Cylindrocarpon

Abstract

The behaviour of conidia of four species of Cylindrocarpon Wollenweber when introduced into soils to which they were both native and alien was studied by means of a buried slide technique. Microconidia of all species germinated infrequently without forming chlamydospores but tended, instead, to be transformed directly into micro-chlamydospores. Macroconidia produced chlamydospores at the end of long or short germ tubes or by the thickening of the walls of some of the cells of the parent spore. Giant chlamydospores resulting from the fusion of macroconidia and the transference of protoplasm from one spore to the other were observed in C. radkicola and C. album. In sterile soil percentage germination was high and most cells of the macroconidia produced germ tubes. Production of chlamydospores was associated with the progressive lysis of conidia and mycelium, but often lysis was initiated before conidia could produce such spores. Bacteria associated with lysed spores were isolated and identified. Corynebacterium sp. was very active in this respect, whereas B. cereus var. mycoides (Flugge) Smith et al. was ineffective. Differences in the lytic phenomena associated with different fungi were also noted. It was demonstrated that chlamydospores of C. radicicola required a period of ageing before they would germinate in the vicinity of young roots of Pisum sativum L.; immature chlamydospores in the vicinity of roots were prone to lysis. No directional growth of germ tubes derived from chlamydospores towards pea roots was observed.