Cellular response of blackgram roots to combined infection of Meloidogyne incognita and Fusarium oxysporum

Root-knot nematode, Meloidogyne incognita induced variable number of distinct multinucleated giant cells in the central cylinder of blackgram roots as early as 4 days of inoculation. Within 8 - 16 days of inoculation of Fusarium oxysporum, abundant fungal growth was observed in cortical cells and xylem vessels. Fungal colonization could only be detected in the giant cells with breakdown of adjoining parenchymatous cell walls within 32 - 45 days of inoculation. The nuclei of giant cells were ameboid and dense without the association of the fungus in comparison to the fungal invaded giant cells where the nuclei were small, rounded with little cytoplasm and few cell organelles.