The main producing areas of rice are India, China, Japan, Indonesia, Thailand, Myanmar and Bangladesh. Asian farmers still account for 92% of the world's total rice production. The three largest rice exporters are Thailand, Vietnam and the United States. Major importers include Indonesia, Bangladesh, Philippines, Brazil and some African and Persian Gulf countries. Although China and India are the two largest rice producing areas in the world, most of the rice produced in these two countries is consumed locally, and only a small part is exported to other parts of the world.
As early as the early 1980s, the international research and development of rice biotechnology was carried out with the support of Rockefeller Foundation. Up to now, there are more than 300 patents on rice biotechnology, involving more than 400 organizations and institutions. Since 1993, many countries in America, Europe, Asia and Australia have started field trials of transgenic rice. At present, six genetically modified rice varieties have been approved to varying degrees, involving planting, eating, feeding, importing and processing.
1 herbicide-resistant transgenic rice
At present, American rice growers mainly control weeds through the combination of herbicides, crop rotation, irrigation, tillage and other planting techniques, and glyphosate herbicides are often used to control weeds in rice fields.
Rice lines LLRICE06 and LLRICE62 were developed by Aventis CropScienc Company of the United States. Transgenic rice resistant to glyphosate (the active ingredient of herbicide glyphosate) was expressed by bar gene, and the bar gene encoded glyphosate acetyltransferase (PAT), which made rice resistant to herbicide. At present, this rice variety has been approved for planting, eating and feeding in six countries.
The application of ammonium phosphate leads to the decrease of glutamate and the increase of ammonia in plant tissues, which stops photosynthesis and leads to the death of plants within a few days. In animals, ammonium phosphate also inhibits the same enzyme, but it can be highly degraded by organisms and has no residual activity, so its toxicity to humans and wild animals is extremely low.
The environmental and edible safety of transgenic lines LLRICE06 and LLRICE62 were also studied. Field trials in the United States (1997 to 1998) showed that there was no obvious difference between transgenic rice and non-transgenic rice in agronomic traits, seed germination and diseases and pests. Studies on hybridization show that the hybridization rate of rice is less than 1%, which is also affected by many biological characteristics of rice, including flower morphology, persistence of pollen vitality and lack of insect vectors. In the United States, the wild varieties separated from cultivated rice are common wild rice and Redmi. Ordinary wild rice only exists in the swamp area of Florida, far from the planting area of cultivated rice, so it can not be crossed with cultivated rice. Only Redmi is considered as the only wild rice in the United States that can be affected by gene penetration of transgenic rice. Although the gene drift rate from cultivated rice to Redmi is very low, it can indeed happen. Therefore, the glyphosate-resistant bar gene can penetrate into Redmi, resulting in glyphosate resistance in Redmi population. Studies have shown that the tolerance of hybrid population to glyphosate will not change its adaptability, nor will it increase its weeds (such as germination potential, plant height, disease resistance, fecundity, granularity and dormancy). Even if hybrids are tolerant to glyphosate, existing weed control methods (such as tillage or other herbicides) can effectively control them.
The experiment of LLRICE06 and LLRICE62 strains on non-target organisms showed that no toxic substances were found on beneficial insects, birds and other species that often move in the field, and the population level of these species did not change significantly.
There is no significant difference in the population level of beneficial species between transgenic rice and non-transgenic rice. Except for producing PAT enzyme, these transgenic rice are no different from commercial rice. A large number of studies show that these transgenic rice lines have no obvious negative effects on organisms beneficial to crops or farmland, and will not lead to species extinction.
LLRICE06 and LLRICE62 lines have no new phenotype and can go beyond the existing rice planting range. Therefore, the environmental impact of planting LLRICE06 and LLRICE62 strains is equivalent to that of planting non-transgenic rice cultivation system.
LLRICE06 and LLRICE62 series samples of grains, straws and various processing parts (such as rice husk, brown rice, semi-cooked brown rice, polished rice, rice bran and rice bran oil) produced with and without glyphosate showed that the indexes such as moisture, inorganic salts, fat, protein, dietary fiber and carbohydrate were all within the normal data range allowed by commercial rice varieties. The characteristics of amino acids and fatty acids in grains of these transgenic lines are similar to those of non-transgenic varieties.
Rice contains a small amount of anti-nutritional factors, which are concentrated on rice bran. Except phytate, the rest are denatured by heat. These anti-nutritional factors include: inositol hexaphosphate, which stores phosphorus in plant seeds and chelates calcium, zinc and magnesium in animal digestive tract, thus hindering the absorption of these nutrients; Trypsin inhibitor; Lectin is a kind of protein, which has special affinity for glycoprotein binding sites on cell walls and plasma membranes, and is related to a series of anti-nutritional effects and some pathological diseases. The results showed that the contents of trypsin inhibitor and lectin in non-transgenic LLRICE06 and transgenic llrice 06 were lower than the minimum detection limit, but there was little difference in phytic acid content. A 42-day feeding experiment of male broilers also confirmed that there was no difference in nutritional composition and quality between them.
PAT enzyme did not find any toxic characteristics. It has specific recognition to glyphosate, and no homologous protein has been found in other organisms. In short, a small amount of PAT enzyme in human and animal foods will not have any foreseeable negative effects. Compared with the amino acid sequence database, no PAT enzyme has homology with any known toxic substances or allergens, nor does it have any allergen characteristics. PAT enzyme is unstable to heat and acid, and completely inactivated after steaming at 75℃ for 30 minutes. Or at a PH of less than or equal to 4 for 30 minutes. If cooking does not destroy the enzyme, PAT enzyme will be digested quickly after human consumption. Studies have shown that in the simulated gastric acid environment, PAT enzyme will decompose within a few minutes.
In addition, the transgenic herbicide-resistant rice LLRICE60 1 developed by the company also obtained environmental release and edible/feeding licenses in the United States and Colombia in 2006 and 2008 respectively.
2 insect-resistant transgenic rice
At present, the transgenic insect-resistant rice that has been successfully developed and approved contains Bt foreign genes. Bt gene is a gene isolated from Bacillus thuringiensis, which can express insecticidal protein.
In 2005, the transgenic rice resistant to Chilo suppressalis developed by Iranian Institute of Agricultural Biotechnology was allowed to be planted, eaten and raised in the country. The rice strain contains synthetic cry 1Ab foreign gene, which is a Bt gene. ?
In 2009, China Huazhong Agricultural University cultivated transgenic rice resistant to LEPIDOPTERA pests through Agrobacterium-mediated method (cry 1Ac event), and obtained the safety certificate for planting, eating and feeding in China.
3 anti-pollen allergic transgenic rice
In 2007, transgenic rice resistant to pollen allergy (7Crp# 10 and 7Crp#242-95-7) developed by Japanese National Institute of Agricultural Sciences was approved for planting in China. Both strains contain pollen protein genes Cryj I and Cryj II. The gene encodes an artificial amino acid sequence, which can be recognized by cedar specific allergen T cells in human body. The rice strain containing this gene can cause antigen reaction, which is helpful to reduce pollen allergic reaction.
4 golden rice
Golden rice is a cultivated rice variety that can synthesize β -carotene (the precursor of vitamin A) through genetic engineering. This variety was developed as a functional food in areas with insufficient vitamin A intake, with the purpose of meeting the intake of vitamin A by some people who take rice as their staple food and avoiding various diseases caused by vitamin A deficiency. In 2005, a new variety, Golden Rice No.2, was successfully developed, and its β -carotene was 23 times that of Golden Rice.
The research and development of golden rice was initiated by Professor Ingo Potrykus from the Institute of Plant Science of Swiss Federal Institute of Technology and Peter Beyer from the University of Freiburg in Germany in 1992 * *. When it was officially released in 2000, golden rice was considered as a remarkable breakthrough in the field of biotechnology because researchers improved the whole biosynthetic pathway. It is realized by transforming two β -carotene synthesis genes into rice, which are from narcissus and Erwinia in soil.
Golden rice has been bred and hybridized with local varieties in Philippine and Taiwan Province provinces and rice variety "Cocodrie" in the United States. These varieties were first tested in the field at Louisiana State University in 2004. The preliminary results show that golden rice planted in the field can produce 4-5 times more β -carotene than golden rice planted in the greenhouse. In 2005, Syngenta Biotechnology Company combined crt 1 gene in golden rice with lycopene synthase gene in corn to develop Golden Rice 2. This variety can produce 23 times the carotene of super golden rice, reaching 37μg/g, of which β -carotene reaches 365,438+0 μ g/g.