Water-facilitated transport of a pimaricin-resistant strain of Mucor hiemalis in the rhizosphere of groundnut ( Arachis hypogaea L.) in a Malawian ferric luvisol

Abstract

A pimaricin-resistant strain of Mucor hiemalis Wehmer was applied as spores to the hypocotyls of groundnut ( Arachis hypogaea L.) and to non-planted soil 12 days after sowing in field conditions in Malawi. Its subsequent distribution in the root zone was followed by selective reisolation over 51 days and related to measured rainfall and soil physical characteristics. The fungus spread to a maximum recorded depth of 58cm on the tap root, much further than any previous reported distance for water-infiltration of fungal spores in soil. Transport in soil adjacent to tap roots and detection at depth on root laterals was much less (max. 22 and 9 cm, respectively) and detectable movement was negligible in non-planted soil. Mechanisms of spore transport on roots are suggested and some previously proposed factors are reinterpreted. The findings indicate considerable potential to manipulate the rhizosphere microbial populations by seed inoculation under tropical climatic conditions.