Inoculation of Euphorbia lathyris with cotton strings infested with Macrophomina phaseolina, causal agent of charcoal rot disease

Abstract

Root infections caused by Macrophomina phaseolina were initiated under optimal conditions for the host, Euphorbia lathyris. Two-week-old Euphorbia lathyris seedlings were inoculated by tying roots with cotton strings infested with Macrophomina phaseolina. Ninety-three per cent of the inoculated roots developed infections after 2 weeks incubation in silica sand at 25 °C. By using infested strings, differences in the incidence of lesion development were detected when infected roots were subjected to differing temperature regimes. After approximately 6 weeks, there was a significantly [Formula: see text] greater incidence of lesion development at 34 °C than at 25 °C, whereas there was no difference in the incidence of infection. Aerial symptoms indicative of charcoal rot were not observed during the course of these studies. Key words: infested strings, charcoal rot.