Resistance to Columbia root-knot nematode inSolanum ssp. and in hybrids ofS. hougasii with tetraploid cultivated potato

Several tuber-bearingSolanum species were screened for resistance to races 1 and 2 of Columbia root-knot nematode,Meloidogyne chitwoodi. Reproductive factor (Rf = Pf/Pi) was assessed and used to infer host resistance. Several clonal selections in one Plant Introduction accession ofSolanum hougasii showed high levels of resistance to both races. Crosses ofS. hougasii with tetraploid breeding clones yielded 14 vigorous F1 hybrids. Three of these interspecific hybrids expressed non-host (Rf 1.0) to race 2. Three hybrids were good hosts to both races, and one was a poor host to race 1 and non-host to race 2. The occurrence of resistance to both races in the F1 hybrids indicates success in the first step of introducing resistance to races 1 and 2 ofM. chitwoodi to the cultivated potato gene pool.