Submitted to: American Journal of Potato Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/29/2004
Publication Date: 12/15/2004
Citation: Brown, C.R., Mojtahedi, H., Bamberg, J.B. 2004. Evaluation of Solanum fendleri as a source of resistance to Meloidogyne chitwoodi. American Journal of Potato Research. 81:415-419. Interpretive Summary: Potato has many wild relatives that can be sources of traits that reduce the cost of production if the traits can be incorporated into new varieties by breeding. We performed a survey in a wild species that has a distribution stretching from the Southwest of the United States down into Northern Mexico. We examined the collections of this wild species for resistance to Columbia root-knot nematode, a pest that requires the application of soil fumigants in order to prevent unacceptable damage to the crop. The nematode causes bumps on the surface of the potato and brown spots in the flesh that prevent the potato from being processed. A grower may spend as much as $350 per acre on soil fumigation. Our results found that at two locations in Arizona plants were resistant to Columbia root knot nematode. These were the only locations, out of twelve examined, that had resistance. This wild species was not directly crossable with cultivated potato so we performed bridging crosses that will produce crossable breeding lines. The products of the bridging crosses were equally resistant as original materials. This resistance can help growers in the Pacific Northwest to avoid $ 40 million of damage caused by the Columbia root-knot nematode and substantially reduce the $20 million fumigation bill incurred on an annual basis.
Technical Abstract: 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 U.S.