AFLP analysis reveals low genetic diversity of Phytophthora austrocedrae in Patagonia, Argentina

VÉLEZ, M.L.; COETZEE M.P.A.; WINGFIELD M.J.; RAJCHENBERG M.; GRESLEBIN, A.G.

Córdoba

Congreso; 6th Workshop of IUFRO Working Party 7.02.09 Phytophthora in Forests and Natural Ecosystems; 2012

IUFRO, Universidad de Córdoba

Phytophthora austrocedrae is a recently discovered pathogen that causes high levels of mortality of Austrocedrus chilensis in Patagonia. The susceptibility of the host tree together with the dispersal pattern of the pathogen in Patagonia led to the hypothesis that P. austrocedrae was introduced into Argentina. But the genetic diversity of the pathogen that would better inform this question has not been determined.  The aim of this study was, therefore, to assess the population structure of P. austrocedrae isolates from Argentina in order to gain an understanding of the origin and spread of the pathogen. Genetic diversity was determined based on amplified fragment length polymorphisms (AFLPs). In total, 48 isolates of P. austrocedrae were obtained from infected A. chilensis trees, and these represented the geographical range of the host. Four primer combinations were used for the AFLP analysis.  Of the 332 scored bands, 12% were polymorphic. Gene diversity (h) ranged from 0.0050-0.0258 and the Shannon index (I) from 0.0180-0.0432. A high degree of genetic similarity was observed among the isolates (pairwise S values= 958-1; 0.993± 0.009, mean±S.D). A frequency histogram showed that most of the isolate pairs were 100% similar. Principal coordinate analysis using three-dimensional plots did not group any of the isolates based on their geographical origin. The low genetic diversity (within and between sites) and absence of population structure linked to geographic origin, suggest that P. austrocedrae was introduced into Argentina.