Yeasts from the leaves of pasture plants

Abstract

The yeast population upon the leaves of pasture plants in New Zealand has been investigated in relation to season, soil yeast flora, and incidence of facial eczema toxin in autumn pasture. Leaf yeasts were shown to be taxonomically distinct from soil yeasts and to vary with season but not to vary with the localities sampled. During most of the year numbers of yeasts varied between 30,000 and 3,500,000 per gramme of leaves, wet weight, but in the February-March period they reached peaks of up to 100,000,000 per gramme, making up about 1 % of the weight of the leaf sample. At this time up to 90 % of the yeast population consisted of red pigmented species. The pattern was altered when autumn rain produced fresh pasture growth, both the total numbers and the proportion of red species dropping. The bulk of this single group of organisms which may be present on normal pasture suggests that it may be necessary to think of pasture as a microcosm rather than as a limited number of higher plants.