Evaluation of Solanum fendleri as a source of resistance to Meloidogyne chitwoodi

Twelve accessions of Solanum fendleri collected in the United States and Mexico were inoculated with 5,000 eggs of host-races 1 and 2 of Meloidogyne 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) for M. chitwoodi race 1. The results were uniformly confirmed in the second experiment. No resistance was found to race 2. The tetraploid S. fendleri accessions were crossed to a nematode-susceptible cultivated diploid potato clone from a S. phureja-stenotomum 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 lower-elevation Sonora-type desert habitat. These accessions are the only known sources of resistance to M. chitwoodi from wild Solanum species in the USA.