Pathological Relationship of Meloidogyne hapla and Phytophthora megasperma F. Sp. Medicaginis in Medicago sativa L.: Importance of Inoculation Timing, Soil Texture, and Temperature


  • G. D. Griffin
  • F. A. Gray
  • D. A. Johnson
  • D. L. Crebs


Alfalfa, Medicago sativa, Meloidogyne hapla, Nematode Resistance, Phytophthora megasperma f. sp. Medicaginis, Phytophthora Root Rot, Reproductive Index, Root-Knot Nematode, Shoot Weight, Soil Texture, Survival, Temperature


The effects of inoculation timing, soil texture, and temperature on the interaction between Meloidogyne hapla and Phytophthora megasperma f. sp. medicaginis were studied on three alfalfa cultivars. Plant survival of cultivars 'Deseret' (susceptible to both pathogens) and 'Apollo II' (resistant only to the fungus) decreased, and plant growth was suppressed compared to uninoculated controls when inoculation with M. hapla preceded inoculation with P. m. f. sp. medicaginis. Survival and growth of 'Nev Syn XX' (resistant to both pathogens) were affected little or none by any inoculation treatment. Survival of Deseret inoculated with both pathogens was less in clay loam soil than in sandy loam soil, and shoot growth was suppressed in sandy loam, sandy-clay loam, and clay loam soils. Nematode reproduction and root galling induced by M. hapla were not affected when inoculation with M. hapla preceded inoculation with the fungus, but increased as a result of preinoculation with the fungus. Whe