Effect of placement of inoculum in soil on infectivity and disease protection ability of a sterile red fungus

Abstract

The effects of variations in the placement of inoculum in soil on the infectivity and disease protection ability of a sterile red fungus (SRF) was investigated. The ability of the SRF to spread in soil and to infect wheat plants either from pre-infected wheat plants or from an introduced source of inoculum was also examined. Experiments were carried out by placing the SRF inoculum at different distances (0, 1, 3, 5, 7 or 9 cm) from the plant and at different depths (0, 2, 4, 6, 8 or 10cm) in soil. Nylon mesh bags used in this study allowed the passage of fungal hyphae but prevented the free movement of wheat roots in soil. The furthest distance for the placement of the SRF inoculum for successful root colonization was found to e 3 cm. This distance was used to detect the differences in the period required to infect and colonize the wheat roots by the SRF in comparison with the take-all fungus. It was observed that the SRF maintains the initial advantage of early arrival on the wheat roots for protecting the plant from the take-all fungus. The SRF was also found to colonize and protect plant roots more effectively when it was placed below the seed at sowing than at a 3 cm distance from the plant. Although the potential for the SRF to spread from plant to plant exists, it may still be necessary to introduce the SRF inoculum close to each wheat seed at sowing.