A GENE-FOR-GENE MODEL TO EXPLAIN INTERACTIONS BETWEEN CULTIVARS OF STRAWBERRY AND RACES OF PHYTOPHTHORA-FRAGARIAE VAR FRAGARIAE

A gene-for-gene model is postulated to explain the observed interactio ns between cultivars of strawberry and races of Phytophthora fragariae . Five interacting resistance (R1-R5) and avirulence (Avr1-Avr5) facto rs explain all the available data involving 15 host genotypes, includi ng the USA and Canadian differential series, and 12 pathogen isolates from North America. Interactions between pathogen isolates and UK and German differentials are also explained by the proposed model. The mod el makes it possible to develop a universally applicable differential series, to present a systematic, unequivocal nomenclature of races, an d to increase the efficiency of breeding programs.