Histopathogenesis of Galls Induced by Meloidogyne naasi in Wheat Roots.

Histopathogenesis of galls induced by Meloidogyne naasi in wheat roots was studied. Large numbers of larvae penetrated wheat root tips within 24 hr; larvae migrated both inter- and intracellularly, causing cortical hypertrophy. Giant cells were formed in the stele around the head of each nematode within 4 to 5 days. Initial pathological alterations in giant cell formation consisted of hypertrophy of protophloem and protoxylem cells, their nuclei and nucleoli. Giant ceils contained 2 to 8 agglomerated multinucleolate nuclei. Synchronous mitotic divisions were first observed 9 days after inoculation. After 21 days, giant cells became highly vacuolate. Observations 40 days after inoculation revealed a complete degeneration of cell contents in many giant cells but their thick walls remained intact. Abnormal xylem completely surrounded the degenerated or partially degenerated giant cells.