( 2010) formally described EC-2 and EC-3 as a distinct species, Phytophthora andina. More recently, two additional lineages were found in Ecuador, EC-2 and EC-3, which cause late blight on non-tuber bearing Solanum species such as S. betaceaum, S. quitoense, S. hispidum and S. muricatum (Ordoñez et al., 2000 Adler et al., 2004). The EC-1 lineage is predominant on potatoes and the US-1 on tomatoes (Forbes et al., 1997 Oyarzún et al., 1998). Two clonal lineages, EC-1 and US-1, both of the A1 mating type, have been identified already in the previous century (Forbes et al., 1997). Studies on Phytophthora associated with Solanaceae in Ecuador showed the presence of four clonal lineages based on the RFLP fingerprinting pattern (Forbes et al., 1997 Adler et al., 2004). Among the genotypic markers used are allozymes, restriction fragment length polymorphisms (RFLPs), mitochondrial haplotypes, amplified fragment polymorphisms (AFLPs) and simple sequence repeats (SSRs or microsatellites) (Fry et al., 2009). This evaluation is based on the reaction of P. infestans isolates with Solanum plants carrying specific resistance genes, and grouping those with the same virulence phenotype as races. For virulence studies, a set of potato genotypes with different R genes is used (Black et al., 1953 Malcolmson & Black, 1966). The mating type is based on the fact that P. infestans is heterothallic, so two types, A1 and A2, are necessary for sexual reproduction (Forbes, 1997).
Among the phenotypic markers used are mating type and virulence. Diversity within and among P. infestans populations has been studied using phenotypic and genotypic markers. It is the most important disease on potato in Ecuador and worldwide (Oyarzún et al., 2002). The oomycete Phytophthora infestans is the causal agent of late blight and attacks a range of species in the Solanaceae family.
0 kommentar(er)
