Survival of chlamydospores and subsequent development of Mycocentrospora acerina in soil

Abstract

In field plots of fen peat soil, chlamydospores of Mycocentrospora acerina on nylon mesh showed a negligible decline in viability over a 2-year period. When infected pieces of carrot tissue were buried, most of the tissues disintegrated within a few weeks and clumps of chlamydospores remained in an amorphous matrix of lignified cell walls and periderm. In the absence of living host roots, these chlamydospores usually remained quiescent in soil and any germ-tubes rapidly lysed; even with a food-base of carrot tissue, growth through soil was negligible. However, roots of carrot seedlings stimulated chlamydospore germination, caused positive tropic reponses of the germ-tubes, and promoted mycelial growth. If chlamydospores were exhumed and placed on the soil surface in high humidity conditions, they usually formed a short germ-tube with a terminal conidium which was readily detached when immersed in water. Implications of these results are discussed in relation to the pre-harvest infection of susceptible crops.