02120naa a2200253 a 450000100080000000500110000800800410001910000250006024501220008526000090020750001670021652011690038365000200155265000250157265000280159765000130162565300230163865300160166165300250167765300420170270000200174470000130176477300890177718641232018-04-30       2010    bl uuuu     u00u1 u    #d1 aMIRANDA, B. E. C. de  aMating type, mefenoxam sensitivity, and pathotype diversity in Phytophthora infestans isolates from tomato in Brazil.  c2010  aTítulo em português: Grupo de compatibilidade, sensibilidade ao mefenoxam e diversidade de patótipos de isolados de Phytophthora infestans de tomate no Brasil.  aThe objective of this work was to characterize 79 Phytophthora infestans isolates collected in tomato (Solanum lycopersicum) fields, as to mating type, mefenoxam sensitivity, and pathotype composition. The isolates were sampled in 2006 and 2007 in seven Brazilian states as well as in the Distrito Federal. They were characterised as to mating type (n=79), sensitivity to fungicide mefenoxam (n=79), and virulence to three major resistance genes Ph-1, Ph-2, and Ph-3/Ph-4 (n=62). All isolates were of the mating type A1. Resistant isolates were detected in all sampled states, and its average frequency was superior to 50%. No difference was detected in pathotype diversity, neither between subpopulations collected in 2006 and 2007 nor between isolates grouped as resistant or intermediately sensitive to mefenoxam. All major resistance genes were overcome at different frequencies: Ph-1, 88.7%; Ph-2, 64.5%; and Ph-3/Ph-4, 25.8%. Isolates with virulence genes able to overcome all major resistance genes were detected at low frequencies. Tomato breeding programs in Brazil must avoid the development of cultivars with resistance based exclusively on major genes.  aDisease control  aSolanum lycopersicum  aLycopersicon Esculentum  aRequeima  aDisease management  aLate blight  aPathogen variability  aSolanum lycopersicum var lycopersicum1 aSUASSUNA, N. D.1 aREIS, A.  tPesquisa Agropecuária Brasileira, Brasília, DFgv. 45, n. 7, p. 671-679, jul. 2010