Complex of root infecting fungi isolated from maize grown under various tillage practices

Abstract

Maize root rot is common in South Africa and various factors may influence disease severity. Phoma spp., Trichoderma spp., Fusarium spp., Macrophomina phaseolina (Tassi) Goid. and Exserohilum pedicellatum (Henry) Leonard and Suggs are the primary fungi isolated from infected roots. Since soil micro flora are affected by prevailing soil conditions, tillage practices may affect the incidence of soilborne fungi. Field trials, to determine the effect of tillage practices on disease severity, were carried out at Bloekomspruit and Mmabatho during the 1992/93, 1993/94 and 1994/95 seasons. Tillage practices applied were no-till, rip, mouldboard, disc and chisel plough treatments. Fungi were isolated from discoloured and apparently clean root tissue, quantified and identified. Significant interactions between isolation frequencies, effect of seasons and tillage practices were recorded for Fusarium equiseti (Corda) Sacc., Fusarium moniliforme Sheldon, Exserohilum pedicellatum and Phoma spp. at Bloekomspruit and Macrophomina phaseolina and Phoma spp. at Mmabatho. The effects of tillage practices on root discolouration and yield were inconsistent during these seasons at both localities. These inconsistent results may be due to the long period required to modify the soil profile by various tillage practices.