INTROGRESSION OF RESISTANCE TO ROOT-KNOT NEMATODES FROM WILD CENTRAL-AMERICAN SOLANUM SPECIES INTO SOLANUM-TUBEROSUM SSP TUBEROSUM

Crossing experiments were conducted to introduce resistance to the roo t-knot nematodes, Meloidogyne chitwoodi and M. fallax, from various po lyploid Central American Solanum spp. into the cultivated potato, S. t uberosum ssp. tuberosum. The most effort was put into producing tetrap loid hybrids through inter-EBN (Endosperm Balance Number) crosses. Fro m the crosses of tetraploid S. tuberosum (4 EBN) with tetraploid S. st oloniferum and S. fendleri (both 2 EBN), few seeds were derived that l ed to viable plants. III vitro culture of immature seeds also yielded several hybrid plants. From crosses of diploid S. tuberosum (2 EBN) wi th hexaploid S. hougasii (4 EBN) four hybrids were obtained through in vitro culture. Backcrosses were made with selected hybrids and a vari able number of seeds was produced depending on the hybrid genotype. Th e successful introgression of resistance into backcross populations is shown. A scheme is presented for the introgression of traits at a tet raploid level from allotetraploid Solanum species into autotetraploid S. tuberosum through sexual crosses. The relevance of EBN for potato b reeding is discussed.