Influence of Salinity and Root-knot Nematode as Stress Factors in Charcoal Rot of Melon

Abstract

Incidence of Charcoal rot, caused by the soil borne fungus Macrophomina phaseolina, may be increased in some crops by the addition of stress on the host caused by high salinity of soil or irrigation water and infection by plant pathogenic nematodes. Since both of these factors may be problematic in melon production in Arizona, studies were initiated to determine if higher salt concentrations of irrigation water and infection by Root-knot nematode (Meloidogyne incognita) may be involved in recent increased incidences of Charcoal rot of melon. In greenhouse trials, higher concentrations of salts in irrigation water significantly increased the percentage of plants that died due to Charcoal rot. However, no significant difference was found in the percentage of dead plants inoculated with both root-knot nematode and M. phaseolina compared to plants inoculated with M. phaseolina alone. Results of these trials indicate that salinity may be a factor in the increased incidence of Charcoal rot of melon, but that root-knot nematode infection may not play a role.