| Popis: |
Mature (three-week) and immature (five-day) sexual progeny were raised from two matings between isolates of Phytophthora infestans with 2C-DNA content (and therefore presumed diploids) but which differed for isozyme genotype and restriction fragment length polymorphisms (RFLPs) in their mitochondrial DNA (mtDNA) and nuclear DNA (nDNA). Approximately 90% of the progeny which were derived from mature oospores, but approximately 50% of the progeny from immature oospores, were classed as hybrids on the basis of their Gpi 1 genotype. All single-oospore cultures, whether derived from a mature or an immature oospore, contained a single mtDNA type from either the A1 or the A2 parent. All single-zoospore lines derived from a single germ sporangium of a germinating hybrid oospore also had the same mtDNA type, Gpi 1 genotype and mating type. These data suggest that mtDNA is inherited uniparentally in P. infestans with no evidence for segregation, elimination or recombination of types. Mating type segregated differently in hybrid offspring; those with type II mtDNA (from the A1 parent) had a preponderance of A1 mating type. Some nRFLPs also segregated unexpectedly in the population with type II mtDNA, suggesting that any bias in the segregation of mating type is caused by viability disturbance rather than linkage between mating type gene(s) and mtDNA. |
