EXPRESSION OF RESISTANCE TO THE ROOT-KNOT NEMATODES, MELOIDOGYNE-HAPLA AND M-FALLAX, IN WILD SOLANUM SPP UNDER FIELD CONDITIONS

In 1995 two fields in the Netherlands, naturally infested with Meloido gyne hapla (Wageningen) and M. fallax (Baexem), were used to evaluate resistant and susceptible Solanum genotypes under natural conditions. In April, genotypes were planted in circular microplots. Soil samples were taken and analyzed for the occurrence of second-stage juveniles e very six weeks. From August onwards, large differences between resista nt and susceptible genotypes in numbers of juveniles were found in the soil. For all resistant wild Solanum genotypes the level of infection in soil at the end of the growing season in October was equal to or l ower than at the beginning. Glasshouse experiments were performed with the same genotypes and nematode populations (i.e. originally derived from these fields) and the results were comparable with the observatio ns from the field. It is concluded that resistance, as selected in gla sshouse trials, corresponds well with resistant behaviour in the field and that it is worthwhile to transfer the resistance from these Solan um sources to commercial potato cultivars for successful control of ro ot-knot nematodes.