FIGURE 1.

Disease cycle of charcoal rot caused by Macrophomina phaseolina. Microsclerotia present in soil is the primary source of inoculum. Microsclerotia germinate (30–35°C) and form a germ tube followed by the development of an appresoria to penetrates through the host epidermis. Once in the roots, the fungus affects the vascular system, disrupting the water and nutrient transport to the upper parts of the plants. This causes wilting of the plant and a typical grey appearance of stem tissues due to the abundance of microsclerotia. Under severe disease and favourable environmental conditions, a premature death of the host plant often occur. Microsclerotia in root and stem debris return to the soil and can either begin a new disease cycle or survive in soil up to 15 years.