|Grunwald, Niklaus - Nik|
Submitted to: Agrociencia Magazine
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/2/2006
Publication Date: 5/1/2006
Citation: Lozoya-Saldana, H., Perales-Rosas, D., Fernandez-Pavia, S.P., Grunwald, N.J. 2006. Characterization of phytophthora infestans (mont.) de bary. ii. subpopulations obtained from wild solanum species. Agrociencia. 40:325. Interpretive Summary: Phytophthora infestans is the causal agent of potato late blight disease that caused the Irish potato famine. The ability of P. infestans to infect wild species of Solanum (relatives of potato) was investigated in controlled field experiments in 2000. Isolates of P. infestans were obtained from five potato varieties with differing levels of disease resistance. Isolates were compared and characterized for genotype using isozymes. Isolates were also analyzed for sensitivity to the well-studied fungicide metalaxyl. Solanum phureja and S. acaule were susceptible to P. infestans and a range of disease severity was observed on different individuals of these species. The other four Solanum species investiageted were uniformly resistant to the pathogen. Isolates recovered from S. phureja and S. acaule were genetically diverse and generally no host specialization was observed for populations of P. infestans affecting these hosts.
Technical Abstract: In the summer of 2000, isolates from natural infections of P. infestans (P.i.) were obtained from six wild species of Solanum planted ex-profeso under rainfed conditions in the Toluca Valley of México to determine possible host-pathogen specificity and for characterization regarding mating type (MT; A1, A2 ), sensitivity to metalaxyl, and the presence of allozymes of glucose-6-phosphate isomerase (Gpi) and peptidase (Pep). Solanum phureja and S. acaule presented diverse degrees of severity of the disease among individuals of each population. The rest of the species were uniformly resistant to the pathogen. Of 24 isolates from S. phureja, 13 multilocus genotypes were detected, the most frequent of which was the A2 100/100 Gpi and 100/100 Pep (22%) and an A1:A2 ratio of 0.6:1. Nine multilocus genotypes were found in the population of P.i. obtained from S. acaule. The most common one was also A2, 100/100 Gpi and 100/100 Pep (22% of such population too), with a MT proportion of 1:1. In S. bulbocastanum, no particular genotype was more common, and the only MT was A1, nor was there a more frequent genotype found in S. caripense, where the proportion of MT A1:A2 was 0.25:1. The only genotype recovered from S. muricatum was A1 86/11, 92/100 (Gpi, Pep), corresponding to US1. The two isolates from S. andreanum were A1, 86/100 Gpi and 100/100 Pep. Solanum phureja and S. acaule had the greatest frequency of isolates highly resistant to metalaxyl, and to a lesser degree of resistance those of S. caripense and S. muricatum. The isolates from S. bulbocastanum and S. andreanum, two species resistant to P.i., were A1 and susceptible to metalaxyl. All of the homothallic isolates were highly resistant to metalaxyl, and host-pathogen specificity was observed only in S. muricatum.