Virulence and genetic diversity of Pseudocercospora griseola isolates from Paraná state, Brazil

GONÇALVES-VIDIGAL M; CAIXETA M; VALENTINI G; COELHO M; GALVÁN M

Niagara Falls

Encuentro; 26th Biennial Meeting of the Bean Improvement Cooperative (BIC); 2015

Bean Improvement Cooperative (BIC)

The angular leaf spot, caused by the pathogenic fungus Pseudocercospora griseola, is one of the most widespread diseases in common bean (Phaseolus vulgaris L.) producing areas. The use of resistant cultivars is indicated as an effective strategy to control the ALS pathogen. Various resistance genes, named Phg-, conferring race specific resistance to different races of P. griseola have been identified. However, the strength of the resistance is complex, and a pathogen such P. griseola shows high diversity in its virulence. In this work, angular leaf spot differential cultivars were used to characterize P. griseola isolates from infected common bean plants from Ponta Grossa, Paraná state, Brazil. In addition, these isolates were characterized through sequencing of the internal transcribed spacer (ITS) region. The characterization of P. griseola isolates using the ALS differential cultivars allowed the identification of race 63-63, which had not been identified in Paraná state, Brazil. This race is broadly distributed through the Brazilian producing areas and its presence was confirmed in Santa Catarina, Minas Gerais and Goiás states. Phenotypic and molecular data on pathogen variability have supported the separation of P. griseola into two major groups: Andean (P. griseola f. griseola) and Mesoamerican (P. griseola f. mesoamericana) (Guzmán et al., 1999). Therefore, the compatibility of race 63-63 to the Andean and Mesoamerican cultivars, revealed the isolates belong to the Mesoamerican gene pool. The phylogenetic tree based on the DNA sequences of the ITS-rDNA regions evidenced the presence of two major groups. A group of isolates recovered from species P. vitis, P. eucalyptorum and P. paraguayensis, and a group including the P. griseola isolates. The five isolates from Ponta Grossa (PG001-PG005) show high similarity to the P. griseola f. mesoamericana isolates retrieved from the GenBank database, confirming the Mesoamerican origin of the isolates collected in Paraná. On the other hand, the Mesoamerican group was clearly divergent from the Andean isolates previously described in the literature.