CORRECTED - (OFFICIAL)-UPDATE 1-Brazil does not clear use of Bayer GMO soy

(Officially corrects agency's spokeswoman's statement that CTNBio cleared Bayer GMO soy for commercial use)

SAO PAULO Nov 19 (Reuters) - Brazil's biotechnology agency CTNBio said on Thursday it did not approve the commercial planting of a genetically modified soybean variety produced by Bayer (BAYGn.DE), backtracking on an earlier statement that it had approved the variety.

Monsanto's (MON.N) Roundup Ready soy is the only GMO soy approved for commercial use in Brazil, which legalized the use of transgenic crops in 2005, according to the GMO industry nongovernmental organization CIB. GMO products must first be cleared for use by the biotech regulator first, however.

Bayer CropScience's GMO soy variety, if eventually allowed for use, would be the first rival to pose a threat to Monsanto's grip on Brazil's transgenic soy seed market.

Several GMO cotton and corn varieties have been also cleared for commercial planting in Brazil. (Reporting by Roberto Samora; Writing by Reese Ewing)