Leaf rust is one of the main diseases of wheat (Triticum aestivum). In Argentina, Brazil, Paraguay, Uruguay and Bolivia epidemics occur every year, that can cause yield losses up to 50% in susceptible cultivars, if fungicides are not used. In Chile, the importance of the disease is increasing, especially in winter wheat cultivars. In most areas of these regions, the pathogen is present all year, favoring the early appearance of the disease, the development of epidemics, and the selection and establishment of new races. Also, resistance breakdown in commercial cultivars is frequent. The objective of this work was to identify the races of wheat leaf rust fungus that occurred in Brazil in 2002, and to determine their frequency, geographical distribution and changes in virulence. Thirty-eight virulence combinations were identified, grouped in 12 different races, according to the Brazilian system. These races represent a wide virulence spectrum, attacking all the resistance genes of the differential series, although at an intermediate level of virulence to Lr16 and Lr21. Two new virulence combinations were identified, which correspond, respectively, to SPJ-RS and MFT-CT/MFT-HT, according to the North American system of nomenclature. Despite the new types of virulence, the gene Lr19, and the combinations of genes (Lr3+Lr9), (Lr9+Lr16), (Lr9+Lr3ka), (Lr9+Lr21), (Lr16+Lr24), continued to be effective for resistance.
Pyrus communis; P. pyrifolia; Malus spp.; Flexiviridae; ASPV; dot-ELISA; immunoblot; RT-PCR
