02080naa a2200325 a 450000100080000000500110000800800410001910000210006024501060008126000090018752011910019665000230138765000180141065000160142865000190144465000120146365000170147565000190149265000230151165000100153465300140154465300140155865300090157265300140158170000220159570000210161770000210163870000200165977300750167918543942022-06-06       2010    bl uuuu     u00u1 u    #d1 aDIAS NETO, J. J.  aHot spots for diversity of Magnaporthe oryzae physiological races in irrigated rice fields in Brazil.  c2010  aAbstract ? The objective of this work was to evaluate the Magnaporthe oryzae pathotype diversity in new commercial irrigated rice fields in the Araguaia River Valley, state of Tocantins, Brazil. The causal agent of rice blast has heavily affected rice production in the region. Despite the efforts of breeding programs, blast resistance breakdown has been recorded shortly after the release of new resistant cultivars developed for the region. Among the causes of resistance breakage is the capacity of the fungus to rapidly develop new pathotypes. A sample of 479 M. oryzae monosporic isolates was obtained and tested using the international rice blast differential set. Isolate collections were made in small areas designed as trap nurseries and in scattered sites in their vicinity. Analysis of 250 M. oryzae isolates from three trap nurseries indicated the presence of 45 international M. oryzae races belonging to seven pathotype groups (IA-IG). In the isolates tested, 61 M. oryzae pathotypes belonging to all but the IH group were detected. The new areas of irrigated rice in the Araguaia River Valley have the highest diversity of M. oryzae pathotypes reported so far in Brazil.  aMagnaporthe oryzae  aPathogenicity  aPyricularia  aArroz irrigado  aBrusone  aOryza sativa  aPatogenicidade  aPyricularia oryzae  aRaça  aPathotype  aPatótipo  aRace  aTocantins1 aSANTOS, G. R. dos1 aANJOS, L. M. dos1 aRANGEL, P. H. N.1 aFERREIRA, M. E.  tPesquisa Agropecuária Brasileiragv. 45, n. 3, p. 252-260, mar. 2010.