Life cycle, pathogenicity, histopathology, and host range of race 5 of the barley root-knot nematode.

The optimum temperature for development of race 5 of Meloidogyne naasi was 26 C. A life cycle was completed in 34 days. Growth of sorghum was suppressed when inoculated with M. naasi. Observations of M. naasi-infected sorghum roots demonstrated that roots were penetrated just behind the root cap; giant cells were generally initiated either in the procambial region or in very young phloem. When giant cells developed in the cortex, corresponding areas of the vascular system did not have an endodermis, pericycle, or phloem fibers. Nineteen plant species were tested for suitability as hosts for race 5 of M. naasi. Reproduction occurred on 11 of 12 monocotolydenous hosts and none of 7 dicotolydenous hosts. Reproduction often occurred without gall development.