MECHANISM OF SUPPRESSION OF MELOIDOGYNE HAPLA AND ITS DAMAGE BY A GREEN MANURE OF SUDAN GRASS

Authors: Widmer, Timothy; ABAWI, G. - CORNELL UNIVERSITY

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2000
Publication Date: 5/1/2000
Citation: Widmer, T.L., Abawi, G.S. 2000. Mechanism of suppression of meloidogyne hapla and its damage by a green manure of sudan grass. Plant Disease. 84:562-568.

Interpretive Summary: Nematodes are nonsegmented, microscopic worms which can penetrate into and cause damage on plant roots. One species, 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 a compound which is broken down to release hydrogen cyanide and a secondary chemical. Sudan grass extracts were prepared by blending the grass with water. 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. When eggs were exposed to a level of cyanide equal to that found in the extract 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 the secondary chemical did not reduce J2 penetration into roots. Exposing eggs to purified Sudan grass extract showed cyanide present only in active fractions. These results suggest that cyanide is the primary factor involved in the suppression of M. hapla by a green manure of Sudan grass.

Technical 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- hydroxybenzaldehyde (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 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 HBA did not reduce J2 penetration into roots. After purifying Sudan grass extract through size-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.