|Title||Formation, production and viability of oospores of Phytophthora infestans from potato and Solanum demissum in the Toluca Valley, central Mexico|
|Publication Type||Journal Article|
|Authors||Flier, WG, Grünwald, NJ, Fry, WE, Turkensteen, LJ|
|genetics, inheritance, populations, resistance, segregation, sympatric speciation, virulence|
Aspects of the ecology of oospores of Phytophthora infestans were studied in the highlands of central Mexico. From an investigation of a random sample of strains, it was found that isolates differed in their average capability to form oospores when engaged in compatible pairings. Most crosses produced large numbers of oospores but a few yielded none and some yielded only a few oospores. The results reveal that oospore production and fecundity is dependent on both isolates and the combining ability of a specific combination of parental strains. On average, 14% of the oospores produced were viable as determined by the plasmolysis method. Viability ranged from a low 1% in one cross to a high of 29% in another cross. Oospores were found in 10-20% of naturally infected Solanum demissum leaves from two different collections, and leaflets with two lesions per leaflet produced more oospores than did leaflets with 3-5 lesions per leaflet. There was no consistent trend for preferential mating between isolates from the same location or host.