Molecular Diversity of Puccinia melanocephala Populations

AFLP analysis was carried out to assess genetic variability and determine the population structure of the sugarcane rust Puccinia melanocephala in northwest Argentina. Molecular data were also used to clarify whether genetic variation was correlated with host variation and/or the geographic distribution of the disease. Bulk rust uredospores were collected in the field, and both the geographical area and the infected host sugarcane cultivar were recorded. A total of 538 AFLP markers generated with 20 primer combinations were used to perform the genetic analysis. The percentage of polymorphic loci was quite high (85.7%), considering that P. melanocephala only reproduces asexually. Cluster analysis (UPGMA) and principal co‐ordinate analysis (PCoA) grouped populations from distinct geographic and host origins, suggesting that neither geographical region nor sugarcane variety constrains the relationships among the populations. This finding was corroborated by a lack of significant correlation between genetic distance and geographic distance (r = 0.057; P = 0.285). The non‐significant differences found between rust populations collected from distinct sugarcane varieties (PhiT = 0.026; P = 0.06) also support these results. Analysis of Molecular Variance Approach (AMOVA) analysis attributed most of the variation (95%) to differences within populations. No genetic structure was detected, and the populations behaved as a large undifferentiated population with high level of genetic variability.