Submitted to: American Journal of Potato Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/20/2000
Publication Date: N/A
Citation: Interpretive Summary: New forms of the "late blight" disease that caused the Irish Potato Famine have cost US potato farmers hundreds of millions of dollars in additional fungicides in recent years. A very attractive solution to this problem is breeding new varieties with built-in genetic resistance to the fungus. Very potent resistance is found in wild relatives of the commercial potato and other breeding stocks from foreign countries. This research used a greenhouse test to find highly resistant plants within promising populations. By identifying the most promising sources of late blight resistant breeding parents, this work will help potato breeders develop resistant varieties and provide them to growers.
Technical Abstract: A greenhouse screen provides a relatively quick means to assess foliar late blight reactions on whole plants and thus, allows for many individuals to be evaluated. Greenhouse assays were carried out to characterize accessions previously reported to be late blight resistant and to identify individuals within the accessions that have high levels of resistance to late blight that can be exploited in breeding programs. A US-8 genotype A2 mating type of Phytophthora infestans was used to inoculate wild Solanum species accessions or hybrid cultivated potatoes x wild species (diploid or tetraploid) from Mexico, Russia or South America. A total of 618 genotypes were evaluated from 1997 to 1998. The percent area of stems and leaves infected with late blight was scored at 7 and 14 days after inoculation. Mexican accessions were significantly more resistant to late blight than either Russian or South American accessions and they were also more uniformly resistant to late blight. Selected genotypes of Russian and South American accessions were retested in 1998 and resulted in the selection of 56 genotypes with potential use in a potato breeding program for resistance to late blight. Among these species, S. microdontum had the highest level of late blight resistance with 28 (50%) selected genotypes from three accessions. The potential use for these species and breeding strategies for late blight resistance are discussed.