Evidence of low levels of genetic diversity for the Phytophthora austrocedrae population in Patagonia, Argentina

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

PLANT PATHOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2014 vol. 63 p. 212 - 220

0032-0862

Phytophthora  austrocedrae  is  a  recently  discovered  pathogen  that  causes  severe  mortality  of Austrocedrus  chilensis  in Patagonia. The high level of susceptibility of the host tree, together with the distribution pattern of the pathogen, have led to the hypothesis that P. austrocedrae was introduced into Argentina. The aim of this study was to assess the popu- lation  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, representing 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  001  to  003;  the  Shannon  index  (I)  ranged  from  001  to  004.  A  high  degree  of  genetic  similarity  was  observed  among  the  isolates  (pairwise  S  values =  0958?1;  0993  0009,  mean  SD).  A  frequency histogram showed that most of the isolate pairs were identical. 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,  together  with the  aggressiveness  of  the pathogen and the disease progression pattern, suggest that P. austrocedrae might have been introduced into Argentina.