The grains producers' association in Brazil's top soybean-growing state, Mato Grosso, warned farmers this week not to plant a new variety of transgenic soy it says Monsanto Co. (MON) has been distributing. The soybean variety, Intacta RR2 Pro, hasn't been approved in China, where more than two-thirds of Brazil's exports of the oilseed are shipped. Mato Grosso state soybean and corn producers' association Aprosoja said in a statement Monday that farmers using Intacta RR2 seeds could accidentally contaminate shipments of approved soybean varieties, putting exports to China at risk of being refused. Monsanto responded Tuesday, saying the company hasn't allowed commercial sales of Intacta RR2 in Brazil and won't do so until all of the country's main export markets approve it. A stockpile of 600,000 sacks of the seeds, which Monsanto had produced based on the belief that China could approve Intacta RR2 "at any time," will be destroyed, the firm added. Aprosoja said Monsanto had been handing out samples of the new seeds to farmers in Mato Grosso and required them to sign a waiver accepting responsibility for any contamination that occurred.