Abstract
The mode of infection of charcoal rot Macrophomina phaseolina was studied employing light and transmission electron microscopy.
When this pathogen was inoculated in sunflower seedlings, it changed the color of root tips. Staining of semi thin section of roots with
methylene blue separated fungal mycelium from plant tissue. Initially, infection was restricted to root epidermal cells but in later
stages the infection was also observed in cortical cells. At this stage cell configuration including organelles became distorted.
Micrographs also revealed sclerotia and development of appressoria. Intercellular spaces were occupied by the fungal hyphae, which
appeared amorphous, with intracellular invasion occurring later. It is envisaged that the development of fungus within the host plant is
accompanied by the production of certain exudes, which helps fungus in penetration and destruction of the host.
