Resumo Procedeu-se a observações histológicas de raízes de pimenta-do-reino, variedade Singapura parasitadas por Meloidogyne incognita. A penetração das larvas de segundo estádio, o mecanismo de formação das células gigantes, etapas do ciclo de vida do nematóide. suscetibilidade e outros aspectos biológicos envolvendo o complexo hospedeiro x parasita foram estudados.

Summary Histological observations made from roots of black pepper (Piper nigrum L.) variety Singapura parasitized by the root-knot nematode, Meloidogyne incognita (Kofoid & White, 1919) Chitwod, 1949, revealed an interesting host — pathogen relationship. It is concluded that the greatest penetration of the secondstage larvae occurred in the apical meristemmatic root region. The initial formation of the giant cells, as well as their development, seems to occur via (1) dissolution of the adjacent root cell walls with later fusion of the cellular contents and (2) successive mitoses without cytokinesis. The high susceptibility of the black pepper variety Singapura to the root-knot nematode, M. incognita, was characterized by vigorous syncytia formed in the vascular tissue causing its disorganization, lack of necrosis surrounding the adult female nematodes or syncytia, and abundant egg mass production.