The high crops output from seeds of foreign firms attracts Chinese vegetable growers. To plant one mu (Chinese unit of area, with one hectare equal to 15 mu) of tomatoes, a farmer will need to spend 1,200 yuan for foreign seeds, but just 20 yuan for domestic equivalents.

Yet the output of the vegetable from foreign seeds will be 10,000 yuan to 20,000 yuan more than that of domestic seeds, according to Ma.

"Seeds contribute more than 50 percent to increases in output and quality. If seeds are controlled by others, national security will be threatened," Sun warned.

Some experts cited problems in the domestic seed industry.

Seed research institutions have access to a lot of government subsidies and have talented staff, but the commercialization of their scientific research achievements needs to be improved, according to Fu Runting, Communist Party chief of the Tianjin Academy of Agricultural Sciences.

"In contrast, it is difficult for private seed companies to obtain government subsidies," said Fu.

Furthermore, growers complain of rampant plagiarism in the sector.

"When we want to sell new types of seeds on the market, we are always in fear of having them copied by others seeking to compete with us," said Ji Heliang, general manager of another Tianjin-based seed firm, Gengyun Seed Company.

The domestic vegetable seed industry needs self-improvement, with more investment and better commercialization of research, Fu believes.

He added that support should be given to private companies, and that intellectual property rights need effective protection.

"The seed industry is basic and needs a strategic view. Otherwise, dangers will come," warned Ma.