Resumo

Rust fungi (Pucciniales) causes some of the most devastating plant diseases and are comprised of more than 7,000 species in over 100 genera. The genus Puccinia is the largest in the Pucciniales and is considered to be the most economically destructive genera of biotrophic fungi. The eucalyptus rust is caused by P. psidii, that is responsible for loses up to 60% in Eucalyptus young plants. Despite of its importance, there are few studies of the genetic variability of the P. psidii populations from different host plants. Thus, our current study evaluated the PCR-DGGE as a tool to access the genetic variability of P. psidii populations sampled in the same area but from different species and hybrids of eucalyptus host (E. grandis, E. urophylla, E. grandis x brassiana, E. grandis x dunni and E. grandis x urophylla). As an out group we used a P. psidii population from guava. Using the PCR-DGGE of the ITS region from rDNA was demonstrated a significant difference among the sampled populations, all those by ANOSIM analyses showed a clear divergence among each other (value R = 1). The guava population showed a lower Shannon and Margalef diversity indexes than the eucalyptus populations and a nMDS analysis demonstrated a clear divergence of this group to eucalyptus populations. The partial sequence of ITS cloned fragment from each population confirmed that all bands generated by PCR-DGGE were from P. psidii ITS region. This data also suggested possible forma specialis detection from E. urophylla population. Moreover, the development of an independent of cultive method to access the genetic variability of this biotrophic fungus will collaborate with the better understanding of the genetic alteration within the pathogen populations resulting in new races and consequently the plant resistance broken. This information will contribute significantly with the advances in the eucalyptus breeding program.