Increased planting of genetically engineered (GE) trees will pose no threat to the environment, Chinese scientists have claimed.
   
Speaking yesterday, experts and officials agreed that the use of modified poplar trees is bound to increase as the country sees surging demands for timber.
   
They insisted the transgenic poplars have already undergone strict safety analysis before being commercialized.
   
"There are many natural and artificial 'restraints' in China to prevent the GE trees from imperiling bio-safety," Lu Mengzhu, a chief scientist with the Chinese Academy of Forestry, said yesterday.
   
Poplars are one of China's most common species of tree. In the late 1990s the country's poplar plantations stretched to 66,600 hectares, said Han Yifan, another senior researcher with the academy.
   
Under harsh natural conditions - dry weather and arid land - of northern China where researchers chose to grow the transgenic poplars, the trees stand little chance of reproducing or "contaminating" natural forests, said Lu, vice-director of the academy's Research Institute of Forestry.
   
plar-741 trees that have been engineered to resist leaf-eating insects, Fang Xiangdong, director of the Office of Genetically Modified Organism Safety under the Ministry of Agriculture, told China Daily.
   
However, the go-ahead for deployment of GE poplars, which was granted as long ago as 2002, has not led to large scale transgenic forestry in China.
   
Han of the forestry academy, a pioneer in GE tree studies since the early 1980s, said so far only 200 hectares of insect-resistant Poplar-12 have been planted.
   
The Poplar-12 trees are inserted with a naturally occurring toxin called Bt (Bacillus thuringiensis). Insects which eat the leaves are poisoned to death, thus saving the tree from defoliation, she said.
   
The transgenic trees are scattered across northern regions including Hebei, Beijing, Liaoning and Ningxia, she said.
   
The other commercialized transgenic species, Poplar-741, has been planted sporadically over less than 3 hectares across nine provinces and municipalities including Hebei, Beijing, Tianjin and Shandong, said Professor Zheng Junbao who has worked on developing the tree.
   
The plant was engineered by inserting modified Bt and a protein enzyme gene, said Zheng at the Hebei Agricultural University.
   
Both commercialized species are female poplars with altered fertility, meaning they are unable to release pollen into the air, Han and Zheng said.
   
Drifting pollen and vegetative propagation have been cited as major concerns by opponents of GE development.
   
Sze Pang Cheung, campaign manager of Greenpeace, yesterday said he believed pollen and seeds from GE trees could spread over great distances, allowing modified genes to spread from GE trees to their unmodified relatives, a situation which could produce unpredictable ecological results.
   
Countering this argument, Lu said that, unlike in other countries, which have adequate rainfall and favorable soil conditions, the northern parts of China, to which the transgenic plants are confined, are dry and parched, with poor quality soil.
   
This environment makes it unlikely that seeds and shoots of bioengineered poplars could survive, let alone thrive, he said.
   
"Even in some rare cases where transgenic poplars yield sprouts, the chances are the shoots will be eaten by sheep or cattle, or destroyed by farming activities," the scientist said.
   
And, to make cross breeding with unmodified trees even more unlikely, China has chosen to plant transgenic poplars and conduct its field trials in northern and eastern areas, far away from the country's natural poplar forests, the majority of which lie in the west, Lu said.
   
Bioengineering
   
Speaking yesterday, Zhi Xin, who works with the State Forestry Administration, said he believed biotechnology research, including transgenic studies, should be encouraged and strengthened in China.
   
"In some ecologically fragile areas, it is very difficult to plant forests without using biotechnology," said Zhi of the agency's GE safety office.
   
"Studies in the past dozens of years show it is extremely difficult to control pest infestation through conventional means, such as crossbreeding," Han said. As a result Chinese researchers have resorted to biological methods, ruling out chemical prevention because of the possible negative environmental impact and the tendency of insects to become pesticide resistant.
   
Huang Minren, a leading poplar expert at the Nanjing Forestry University, said rapid economic development and rocketing living standards have stoked up demands for lumber.
   
Poplars, whose various species are fast growing, will play an increasingly important role in easing the stress if pest perils are controlled through bio-engineering, said Huang, who is also vice-chairman of the National Poplar Committee.
   
So far the two commercialized poplar species seem to prove the country's research is pointing in the right direction.
   
The average percentage of defoliation of the transgenic Poplar-12 is less than 20 per cent, a rate well below that of its non-transgenic cousins, Han said.
   
(China Daily April 1, 2005)