| The commercial release of transgenic. herbicide-resistant rice has aroused extensive concerns about environmental biosafety, especially the environmental consequences caused by transgene escape from transgenic herbicide-resistant rice to weedy rice via gene flow worldwide. So it is very important to make a comprehensive and scientific biosafety assessment before the commercialization. The research included comparison of fitness between F1 hybrids and F2 hybrids from cross between six weedy rice accessions and transgenic glufosinate-resistant rice 86B, comparison of fitness between hybrids and parents, comparison of fitness of hybrids under two cropping patterns (directed-seeded and transplanted) and two conditions of selecting pressure (not spraying glufosinate and spraying glufosinate), respectively and segregation for glufosinate resistance and resistant level of F2 hybrids. We studied comprehensively on the fitness of F1 and F2 hybrids harbouring the glufosinate-resistant gene to provide the scientific bases for biosafety assessment of transgene escape from transgenic herbicide-resistant rice to weedy rice.In general, fitness of F1 hybrids was significantly higher than F2 hybrids. Compared with F2 hybrids, F1 hybrids showed better performance at the vegetative stage, with more tillers per plant. F1 hybrids also showed better performance at the reproductive stage, with longer panicles,more filled grains and total grains per panicle, as well as more panicles, filled grains and higher yield per plant than F2 hybrids.Fitness of all F1 hybrids was significantly higher than their weedy rice parents. Compared with their weedy rice parents, F1 hybrids showed better performance at the vegetative stage, with taller plants, more tillers per plant, as well as greater flag leaf length, flag leaf width, flag leaf area and culm diameter. F1 hybrids also showed better performance at the reproductive stage, with longer panicles, higher 100-grain weight, more filled grains and total grains per panicle, as well as more panicles, filled grains and higher yield per plant than their weedy rice parents.Fitness of all F2 hybrids was significantly higher than their weedy rice parents. Compared with their weedy rice parents, F2 hybrids showed better performance at the vegetative stage, with taller plants and greater flag leaf length, flag leaf width, flag leaf area as well as culm diameter. F1 hybrids also showed better performance at the reproductive stage, with longer panicles, higher 100-grain weight, more filled grains and total grains per panicle, as well as more filled gains and higher yield per plant than their weedy rice parents.In general, fitness of F1 hybrids was significantly higher than transgenic glufosinate-resistant rice 86B parent. Compared with transgenic glufosinate-resistant rice 86B parent, F1 hybrids showed equal performance at the vegetative stage. All F1 hybrids were taller and produced more tillers per plant, but showed lower values for flag leaf width, flag leaf area and culm diameter than transgenic glufosinate-resistant rice 86B parent. F1 hybrids showed better performance at the reproductive stage, with longer panicles, more filled grains, total grains and shattering grains per panicle, more panicles, filled grains and higher yield per plant, as well as higher seed shattering and seed setting than transgenic glufosinate-resistant rice 86B parent.In general, fitness of F2 hybrids was significantly higher than transgenic glufosinate-resistant rice 86B parent. Compared with transgenic glufosinate-resistant rice 86B parent, F2 hybrids showed slightly lower performance at the vegetative stage. Although the majority of F2 hybrids were taller and produced more tillers per plant, all of them showed lower values for flag leaf width, flag leaf area and culm diameter than transgenic glufosinate-resistant rice 86B parent. F2 hybrids showed better performance at the reproductive stage, with more shattering grains per panicle, more panicles, filled grains and higher yield per plant, as well as higher seed shattering than transgenic glufosinate-resistant rice 86B parent.Fitness of all hybrids under transplanted condition was significantly higher than under directed-seeded condition. In general, hybrids under transplanted condition showed slightly better performance at the vegetative stage, with taller plants and more tillers per plant than under directed-seeded condition. Compared with under directed-seeded condition, hybrids under transplanted condition showed better performance at the reproductive stage, with longer panicles, more filled grains and total grains per panicle, as well as more panicles, filled grains and higher yield per plant.Fitness of all hybrids under selecting pressure (spraying glufosinate) was significantly higher than under no-selecting pressure (not spraying glufosinate). In general, hybrids under selecting pressure (spraying glufosinate) showed slightly better performance at the vegetative stage, with more tillers per plant than under no-selecting pressure (not spraying glufosinate). Compared with under no-selecting pressure (not spraying glufosinate), hybrids under selecting pressure (spraying glufosinate) showed better performance at the reproductive stage, with more panicles, filled grains and higher yield per plant.Due to the poor genetic compatibility between indica-type rice and japonica-type rice, pollen vitality and seed setting of F1 hybrids from cross between WRDD,WRSY (japonica type) and transgenic glufosinate-resistant rice 86B (indica type) were significantly lower than their weedy rice parents. Although pollen vitality and seed setting of F2 hybrids recovered to some extent compared with F1 hybrids, they were still lower than or similar to their weedy rice parents. Due to the poor seed shattering of transgenic glufosinate-resistant rice 86B parent, seed shattering of most of F1 hybrids was significantly lower than their weedy rice parents. Although seed shattering of most of F2 hybrids recovered to some extent compared with F1 hybrids, it was still lower than their weedy rice parents.Segregation for glufosinate resistance of F2 hybrids deviated from Mendelian segregation, the ratio of resistant individuals was lower than expected. Germination of the seeds of F2 hybrids harbouring the glufosinate-resistant gene soaked by glufosinate solutions was similar to transgenic glufosinate-resistant rices, that indicated the normal expression of the glufosinate-resistant gene in F2 hybrids to make the seeds resistant to glufosinate solutions. Besides, the effect of foliar application of glufosinate solutions on the leaves of F2 hybrids harbouring the glufosinate-resistant gene was similar to transgenic glufosinate-resistant rices, that also indicated the normal expression of the glufosinate-resistant gene in F2 hybrids to make the plants resistant to glufosinate solutions. |
PDF Full Text Request