Evaluation ofSolarium fendleri as a source of resistance toMeloidogyne chitwoodi

Twelve accessions ofSolarium fendleri collected in the United States and Mexico were inoculated with 5,000 eggs of host-races 1 and 2 ofMeloidogyne chitwoodi, Columbia root-knot nematode. The test seedlings that were derived from plant introduction true seed lots were maintained for 55 days before harvest and egg count. The results revealed that two accessions, PI 275162 and PI 275165, were non-hosts (final egg count/initial egg inoculation < 0.1) forM. chitwoodi race 1. The results were uniformly confirmed in the second experiment. No resistance was found to race 2. The tetraploidS. fendleri accessions were crossed to a nematode-susceptible cultivated diploid potato clone from aS. phurejastenotomum population. The triploid hybrids expressed resistance to race 1 at the non-host level. After somatic doubling, the resulting hexaploids also expressed non-host-level resistance to race 1. The two resistant accessions had been collected in southeastern Arizona, one each from the Huachuca and Chiricahua Mountains. Each range is an isolated island of high-elevation mesic flora surrounded by typical lowerelevation Sonora-type desert habitat. These accessions are the only known sources of resistance toM. chitwoodi from wildSolanum species in the USA.