The survival of propagules of Macrophomina phaseoli and Diplodia maydis in Nigerian soils

Abstract

AbstractWeekly isolations from sterile and unsterile soils artificially inoculated with Macrophomina phaseoli and Diplodia maydis showed a decline in numbers of the propagules of these pathogens. Sclerotia of M. phaseoli and spores of D. maydis could not be recovered either on dilution plate or on soil plates after four weeks of inoculation of unsterile soil and after fifteen weeks for D. maydis and twenty‐five weeks for M. phaseoli in sterile soil. In unsterile soil, sclerotia‐like structures were observed with the aid of a light microscope up to the tenth week after soil inoculation by the flotation technique but their viability could not be determined due to active parasitization by Penicillium sp. and Trichoderma sp. The high number of these hyperparasites/g of soil may be responsible for the non‐detection of these pathogens in soils of some maize‐growing states in Nigeria, as well as a reduction in their longevity in soil. It thus seems, from this study, that the host tissue is the site of survival of propagules of these pathogens from one season to another.