Estrutura e desenvolvimento da galha radicular induzida por Meloidogyne javanica em Glycine max L. (soja)

Abstract

Gall-forming root-knot nematodes have been studied in several cultivated species around the world, providing subsidies for understanding the intimate relationship between parasite and the host plant. The establishment of the galling nematode depends of development of the giant cells near the inducing organism to guarantee nourishment. Therefore, species of Meloidogyne induce the development of a feeding site in the cortex or vascular cylinder and the nematodes are totally dependent of this site formation. In this way, we focuses on the anatomical, cytological and histochemical changes during the establishment and development of galls induced by Meloidogyne javanica in roots of Glycine max. The soybean variety used in this study was M8372 IPRO, susceptible to M. javanica. The seeds of G. max were sown in trays and then placed in tubes, where roots were sampled at different stages of development, as inoculated plants as well control plants. The samples of galls and non-galled roots were used for histological, cytological and histochemical analysis in optical and transmission electron microscopy. The galls showed different shapes and abundance in the inoculate roots by M. javanica. The induction of galls occurs by hypertrophy of the root cortex shortly after the initial infection process. Giant cells were formed at 18 days after nematode inoculation. These giant or nourishing cells are multinucleated, have dense cytoplasm, thick wall with invaginations, many mitochondria and small vacuoles. The anatomical sections indicated a disorganization of the cells of the cortex and vascular cylinder in relation to the uninoculated (control) root.