Ultrastructural aspects of the hypersensitive reaction in tomato root cells resistant to Meloidogyne incognita

Resumen

Juveniles of the root-knot nematode, Meloidogyne incognita (Kofoid et White) Chitw., enter the roots of resistant or susceptible plants in the same numbers (Reynolds et al., 1970). In the tomato cv. Hawaii cells around the anterior end of root-knot nematodes were killed within 24 hours of invasion of the roots (Riggs and Winstead, 1959). Rapid death of the cells isolates the nematode and injury is thus confined to a few cells (Rohde, 1972). This incompatible host-parasite interaction (hypersensitive reaction) has been reported as a common type of response in resistant plants for a wide variety of pathogens (Riggs and Winstead, 1959; Rohde, 1965; Klement and Goodman, 1967; Loebenstein, 1972; Brown, 1978; Politis and Goodman, 1978; Heath, 1980 and 1981). Ultrastructural changes that occur during the development of a hypersensitive reaction (HR) in tomato cv. Nematex, resistant to M. incognita, have been described by Paulson and Webster (1972). However, the mechanism by which resistant plants starve parasitic nematodes and prevent their development remains unknown. This study was undertaken to obtain additional data on the ultrastructural changes in response to penetration of M. incognita in the roots of tomato cv. Brech, resistant to this nematode. Histochemical tests were also made to investigate the nature of the material occurring between the cell wall and plasmalemma in cells surrounding the necrosis.