(Adds detail on timeframe)

By Dominique Patton

BEIJING, Nov 15 (Reuters) - China has laid out a clear path for seed makers to get approval for genetically modified crops, under proposed rule changes that should lead to commercial cultivation of GM corn.

Details of the planned regulatory overhaul for the seed industry were published on Friday by the agriculture ministry in a draft document that is open for public comment until Dec. 12.

The proposed changes mean that a handful of recently approved GM traits developed by Chinese companies could be ready for market launch in a year.

"It's a big step," said Liu Shi, a vice president of Beijing Dabeinong Technology Group Co Ltd, which has several GM traits approved as safe and is expected to be one of the first firms to commercialise GM corn in China.

Shares of Dabeinong shares fell 6% on Monday, while those of rival Yuan Longping High-Tech Agriculture Co Ltd fell 10%.

China's leadership called last year for an urgent "turnaround" in the seed industry, which is struggling with overcapacity and rampant infringement of intellectual property that has stifled innovation.

The changes implement decisions by the cabinet and the powerful central committee of the ruling Communist Party on safe management of GMOs (genetically modified organisms) and development of a modern seed industry, the ministry of agriculture and rural affairs said in its statement.

Top policymakers have also urged progress in biotech breeding, or GM crops, seen as key to ensuring food security.

While investing heavily in GM research and development for years, Beijing has remained cautious, barring the planting of GM soybeans or corn, despite allowing imports for use in animal feed.

Once approved, China could plant 33 million hectares with GM corn, estimated Hua'an Securities in a note on Sunday, generating up to 5 billion yuan in income, while also creating strong market leaders and driving rapid consolidation in the industry.

The proposed changes would bring China's regulations more in line with those of other markets.

If a GM trait, also known as an 'event', has already been approved as safe by the agriculture ministry, it can be integrated into an already approved corn hybrid, for example, and only requires a one-year production trial to verify that the combination is still safe.

Previously, it was thought that China might require the product to once again undergo all safety trials from scratch.

"It clarifies the procedures for GMO variety approvals and simplifies the process," said Han Gengchen, chairman of Origin Agritech Ltd, the first Chinese company to develop GM corn crops.