LOSS OF PRODUCTION OF THE ELICITOR PROTEIN INF1 IN THE CLONAL LINEAGEUS-1 OF PHYTOPHTHORA-INFESTANS

The extracellular protein INF1 of Phytophthora infestans is a member o f the elicitin family of protein elicitors known to induce a hypersens itive response on some solanaceous and cruciferous plants. The presenc e of INF1 elicitin in culture filtrates of 102 P. infestans isolates f rom 15 countries was examined. All tested isolates produced INF1 excep t five isolates collected in 1976 and 1977 from infected potatoes in E ast Germany (the former German Democratic Republic). Based on hybridiz ation to the multi-locus DNA fingerprint probe RG57, all the INF1-nonp roducing isolates were shown to belong to the clonal lineage US-1 that dominated world populations until the 1980s. Phylogenetic analysis of a set of European US-1 isolates using amplified fragment length polym orphism fingerprint data indicated that loss of MFI production evolved independently in separate lineages within US-1. DNA and RNA blot hybr idizations showed that INF1-nonproducing isolates still retain a copy of the inf1 gene, whereas little inf1 mRNA could be detected. Hypothet ical interpretations of the evolution in a restricted geographic area of P. infestans lineages deficient in the production of a specific eli citor protein are discussed.