UPDATE 1-Brazil allows planting of Dupont, Dow GMO corn

(Adds background on GMO corn, paragraphs 4-6)

SAO PAULO, Dec 11 (Reuters) - Brazil's biosafety regulator CTNBio approved on Thursday the commercial planting of a genetically modified corn jointly developed by Dupont Inc. (DD.N) and Dow Chemical Co. (DOW.N).

The Herculex corn variety is insect resistant and tolerant to glufosinate ammonium.

It must still be approved by Brazil's Agriculture Ministry before it can be planted.

This is the sixth genetically modified variety of corn approved for commercial planting in Brazil.

The first ones, developed by Bayer BAYG.DE and Monsanto (MON.N), were cleared in late 2007. So the next corn season will be the first one to produce genetically modified types.

They are expected to account for 6.7 percent of the total planted area, according to independent grain analyst Celeres in their first season.

(Reporting by Roberto Samora, Writing by Inae Riveras; Editing by David Gregorio)