During a study on the phylogenetic relationships between species in the Phytophthora cryptogea complex and related species, P. erythroseptica and P. sansomeana, 19 hybrid isolates with multiple polymorphisms in the nuclear sequences were observed. Molecular characterization of hybrids was achieved by sequencing three nuclear (internal transcribed spacers, ß-tubulin, heat shock protein 90) and two mitochondrial (cytochrome c oxidase subunit I, NADH dehydrogenase subunit I) gene regions and cloning of the single copy nuclear gene, ß-tubulin. Based on the molecular studies the hybrid isolates belonged to six distinct groups between P. cryptogea, P. erythroseptica, P. pseudocryptogea, P. sansomeana and P. sp. kelmania. In all cases, only a single cytochrome c oxidase subunit I and NADH dehydrogenase subunit I allele was detected and nuclear genes were biparentally inherited, suggesting that the hybrids arose from sexual recombination events. Colony morphology, growth rate, cardinal temperatures, breeding system, and morphology of sporangia, oogonia, oospores and antheridia were also determined. Some morphological differences between the hybrids and the parental species were noted; however, they were not sufficient to reliably distinguish the taxa and DNA markers from nuclear and mitochondrial genes will to be necessary for their identification. The parental species are all important pathogens of agricultural fields that have been transported globally. With the apparent ease of hybridization within this group there is ample opportunity for virulent hybrids to form, perhaps with extended host ranges.
|Scooped by Alejandro Rojas|
Alejandro Rojas's insight:
It is really interesting since we also found P. sansomeana on corn and soybean, so what are the species of Phytophthora hybridizing in this host/environment? It could be P. cryptogea species complex since it is widely present (most often on tree species).