Histopathology of the nematodes Radopholus similis, Pratylenchus coffeae, Rotylenchulus reniformis and Meloidogyne incognita in plantain (Musa acuminata x M. balbisiana, AAB)

Abstract

Radopholus similis produced sunken lesions that modified the normal cylindrical anatomy of the plantain root under severe necrotic conditions. The lesions caused by R. similis were similar to those caused by Pratylenchs coffeae, except that the latter did not alter the turgid condition of the root. At cellular level, R. similis induced hypertrophy of the nucleus and nucleolus of the cortical cells; however, P. coffeae did not produce a similar reaction. Rotylenchulus reniformis concentrated the parasitic activity on the feeder roots, thus causing necrosis at the feeding site. The reniform nematode induced a syncytia made up mainly of fourteen to twenty longitudinal and circumferential cells of the pericycle.The cells, the nucleus and the nucleolus of the syncytia were hypertrophied. Two nucleoli were observed in some of the syncytial cells. The cytoplasm of the syncytia was granular, dense and had spheric inclusions. A solid and mustache-like structure that we called feeding filter was observed between the feeding cell and the pericycle. The root-knot nematode, Meloidogyne incognita, caused profuse root galls and cortical cracks in the roots and exposition of the internal tissue, mainly at the distal portion of the main roots. Meloidogyne incognita penetrated the endodermis and the pericycle and induced hypertrophy on five to seven of the vascular parenchymal cells with multiple hypertrophied nuclei.