Histopathology of Macrophomina Stem Canker Disease in Pigeonpea (Cajanus cajan L.)

Abstract

Macrophomina phaseolina, causal agent of stem canker disease has recently emerged as an agriculturally important plant pathogen. Macrophomina stem canker disease (MSD), caused by Macrophomina phaseolina is a potentially serious disease in pigeonpea that occurs when reaches physiological maturity i.e., during flowering. The fungus incites necrotic lesions on stem and girdles the plant at the base leading to premature flower drop leading to complete witling and finally death of the entire plant. The mechanisms of infection remain to be fully elucidated. The present study investigated histopathology of MSD caused by M. phaseolina in pigeonpea seed and seedlings using light microscopy. Pigeonpea variety ‘Bahar’ was used in this study. Histopathological sections of seed, stem, root, and leaves were prepared and stained with safranin and trypan blue. Histopathology of the infected plant parts showed the presence of intercellular mycelia and microsclerotia in the cortex and vascular tissues. The germ tube colonized the plant with growth of seedlings following seed coat, cotyledon, stem, root and leaves. According to the results, the pathogen can penetrate and invade the seeds within 24 h post inoculation.