Studies of fungi in pasture soils

Abstract

Abstract Fungi colonising roots of perennial ryegrass (Lolium perenne L.) and of white clover (Trifolium repens L) were studied by microscopical examination and by cultivation of 2 mm segments cut from washed roots. Sampling sites were selected so that comparisons could be made between plants growing in grazed pastures on: (a) soils from similar parent materials but under different climates: and (b) soils from different parent materials but under similar climates. The incidence of hyphae on roots varied with the type of root examined. The incidence of hyphae on old roots was higher than that on young roots. The mycelial population of both plants was composed of a large proportion of sterile hyaline and dark forms and a large group of identifiable fungi, a few species of which showed a high frequency of occurrence in particular soils, i.e., Fusarium oxysporum, Cylindrocarpoll radicicola, Gliocladium roseum, Fusarium culmorum, Absidia spinosa, Mortierella aipina, Penicillium spp. F. oxysporum was the predominant identifiable fungus in warm, moist, moderately acid soils, but was of low occurrence or absent in cool. moist, less acid soils. In the latter soils the occurrence of C. radicicola was high. C. radicicola was not recorded from soils which had a seasonal dry period. Differences in root fungal populations were associated with climate, soil, season, and type of root examined.