Isolates of the US-1 and BR-1 clonal lineages of Phytophthora infestans, collected from tomato and potato fields of two main producing regions of Brazil (south and southeast), were tested for sensitivity to the systemic fungicide metalaxyl, plus the three protectant fungicides mancozeb, chlorothalonil, and cymoxanil. For metalaxyl, one agar test and two leaf-disc tests were carried out. For all tests, metalaxyl insensitive (I), intermediately insensitive (II), and sensitive (S) isolates were detected. There was no association among metalaxyl sensitivity and region, lineage, or host. In the agar test, 35.0% of 210 isolates were classified as I, 36.0% as II, and 29.0% as S. US-1 isolates were classified as 36.1% I, 30.6% II, and 33.3% S. BR-1 isolates were 33.3% I, 23.8% II, and 42.9% S. In leaf-disc test 1 (240 isolates tested), 24.3% were classified as I, 35.0% as II, and 40.7% as S. Isolates of US-1 were 21.0% I, 39.8% II, and 39.2% S, whereas BR-1 isolates were 36.0% I, 20.0% II, and 44.0% S. In leaf-disc test 2 (96 isolates tested), which was based on an effective dose for 50% sporulation inhibition (ED50), most isolates were either I (44.8%) or II (51.0%), and only three (4.2%) were S. The US-1 isolates were 46.0% I, 51.0% II, and 3.0% S. Isolates of the BR-1 lineage were 45.0% I, 52.0% II, and 3.0% S. For mancozeb, the ED50 for 53 of 59 isolates was below 1.0 μg/ml. No isolate grew on medium amended with more than 100 μg of chlorothalonil/ml and the ED50 for 38 of 50 isolates was below 1.0 μg/ml. For cymoxanil, the ED50 for all 47 isolates tested was below 1 μg/ml. There is no evidence of resistance of resistance of P. infestans to protectant fungicides commonly used in Brazil.

Foram caracterizados 123 isolados de Phytophthora infestans obtidos de 21 lavouras de tomateiro e oito de batateira, em municípios do Estado de Goiás e Cidades Satélites de Brasília, no período de abril de 2001 a setembro de 2003. Os isolados foram caracterizados para os marcadores grupo de compatibilidade (123 isolados); isoenzima glucose 6-fosfato-isomerase (Gpi) (34 isolados) e resistência aos fungicidas mefenoxam (77 isolados) e metalaxyl (32 isolados de batateira), usando o método de disco de folhas. Todos os 78 isolados de tomateiro foram classificados no grupo de compatibilidade A1, enquanto os 45 de batateira foram do grupo A2. Os fenótipos para Gpi dos isolados de tomateiro (19) e de batateira (15) foram 86/100, típico da linhagem clonal US-1, e 100/100, típico da linhagen clonal BR-1, respectivamente. Quanto à resistência a mefenoxam, constataram-se isolados de tomateiro resistentes (36%), intermediários (48%) e sensíveis (16%). A maioria dos isolados de batateira foi classificada como sensível (82%) e apenas 9% de intermediários e resistentes. Dos isolados de batateira avaliados para resistência ao metalaxyl, 25% foram resistentes, 62% intermediários e 13% sensíveis. A população de P. infestans no Distrito Federal e no Estado de Goiás é constituída de duas linhagens clonais, com especificidade por hospedeiro.

Aim: Physiological race determination of 143 Fusarium oxysporum f. sp. lycopersici (FOL) isolates collected along 30 years in major tomato-producing regions of Brazil. Materials and Results: Physiological races were determined via root-dipping inoculation of differential tomato accessions and by the PCR-based marker system of Hirano and Arie (2006). According to pathogenicity/virulence assays, five race 1, 23 race 2 and 115 race 3 isolates were identified. FOL race 1 and 2 isolates prevailed up to early 2000s. Afterwards, the large majority of the isolates was classified as the invasive race 3. Novel reports of race 3 were done in five states, thus expanding its geographical distribution. Using this PCRbased marker system, a precise discrimination was observed for all race 3 isolates. However, all race 1 and 2 isolates displayed only the cosmopolitan race 1-specific amplicon pattern. Conclusion:The development and/or validation of novel race-specific marker systems are necessary to allow a precise discrimination of the potentially endemic Brazilian FOL race 2. Significance and Impact of the Study: The present characterization of isolates indicates that distinct evolutionary mechanisms are acting to select new FOL races and/or genetic variants across agroecosystems around the globe. 1982). A repertoire of four dominant resistance factors (I, I-2, I-3 and I-7) has been characterized in distinct tomato accessions (Gonzalez-Cendales et al. 2016;Catanzariti et al. 2017). The I-2 gene from S. pimpinellifolium (located on chromosome 11) controls resistance to race 1 and race 2 isolates, displaying in its structure the nucleotide binding and leucine-rich repeat (LRR) motifs (Simons et al. 1998). The race 1-specific I gene was introgressed from S. pimpinellifolium (also located on chromosome 11) and it encodes an atypical membraneanchored, LRR receptor-like protein (Catanzariti et al. 2017). The FOL race 3 resistance gene I-3 from S. pennellii is located on chromosome 7. The I-3 gene encodes one S-receptor-like kinase and controls resistance to race