ABSTRACT
Meloidogyne hapla is a continuing problem on vegetables in the state of New York. Sudan grass has been demonstrated to suppress infection and damage to susceptible vegetables caused by this nematode when incorporated as a green manure. Some Sudan grass cultivars contain the cyanogenic glucoside dhurrin that is degraded through an intermediate step to p-hydroxybenzal-dehyde (p-HBA) and HCN. Incubating M. hapla eggs in Sudan grass extract resulted in a 55% reduction in the number of juveniles (J2) penetrating lettuce roots. Juveniles exposed to the extracts were not affected. Sudan grass extract affected egg maturation by delaying development, but did not affect hatching. Exposing eggs to a 0.1 ppm CN- solution reduced the number of nematodes that penetrated the roots by 48%, while exposing J2 to the same concentration reduced nematode infection by only 4%. However, exposure of eggs to p-HBA did not reduce J2 penetration into roots. After purifying Sudan grass extract through size-exclusion resin, only the fractions collected that contained cyanide suppressed infection of lettuce roots by M. hapla J2 when eggs were exposed to these fractions. These results suggest that CN- is the primary factor involved in the suppression of M. hapla by a green manure of Sudan grass.
