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 Meloidogyne 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 every six weeks. From August onwards, large differences between resistant 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 lower 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 observations from the field. It is concluded that resistance, as selected in glasshouse trials, corresponds well with resistant behaviour in the field and that it is worthwhile to transfer the resistance from these Solanum sources to commercial potato cultivars for successful control of root-knot nematodes.