SAO PAULO, Sept 26 (Reuters) - Brazil's real currency strengthened almost 1 percent on Wednesday as a poll showed right-wing presidential candidate Jair Bolsonaro in the lead, after previous polls had shown him giving up ground to his main leftist opponent. According to a poll by Brazil's Instituto Parana, 31.2 percent of respondents are planning to vote for Bolsonaro in the first round of the presidential election on Oct. 7, versus 20.2 percent for Fernando Haddad, the leftist protege of jailed former President Luiz Inacio Lula da Silva. Crucially, the poll showed Bolsonaro winning a likely second round later in October, with 44.3 percent of the vote versus Haddad's 39.4 percent. The poll came as welcome news to traders, who generally favor Bolsonaro for his avowed free-market policies, after a separate recent poll had shown Bolsonaro losing in a likely run-off. "The market liked the poll because it showed Bolsonaro rising, not stagnating," said Jose Carlos Amado, a trader at brokerage Spinelli. The real had climbed 0.96 percent against the dollar in afternoon trade. Brazilian equities were effectively flat for much of Wednesday, dragged down by heavily weighted iron ore miner Vale SA and a slew of corruption arrests in the infrastructure sector. Vale shares were off 3.5 percent in afternoon trade, as traders took profits after the firm hit an all-time high on Tuesday. Shares in highway operators Ecorodovias Infraestrutura e Logistica SA and CCR SA were off 3.1 percent and 5 percent, respectively, after police investigated almost 20 people for taking part in a corruption scheme in which both firms allegedly participated. Brazil's benchmark Bovespa equities index was up 0.1 percent in afternoon trade. Key Latin American stock indexes and currencies at 1619 GMT: Stock indexes daily % YTD % Latest change change MSCI Emerging Markets 1041.78 -0.05 -10.07 MSCI LatAm 2509.73 -0.69 -11.26 Brazil Bovespa 78709.90 0.1 3.02 Mexico IPC 49746.40 0.19 0.79 Argentina MerVal 33968.85 -0.25 12.98 Colombia IGBC 12383.73 0.13 8.91 Venezuela IBC 318810.69 -0.28 25139.54 Currencies daily % YTD % change change Latest Brazil real 4.0425 0.96 -18.04 Mexico peso 18.9075 -0.41 Chile peso 661.83 0.68 -7.13 Colombia peso 2996.25 0.19 -0.48 Peru sol 3.304 0.12 -2.03 Argentina peso 38.7200 -0.57 -51.96 (interbank) Argentina peso 38.5 -0.65 -50.05 (parallel) (Reporting by Claudia Volante and Gram Slattery; Additional reporting by Paula Arend Laier Editing by Alistair Bell)