| Among wild relatives,wild B.juncea(AABB,2n=36)is a relative weed which has closer genetic relationship with genetically modified(GM)oilseed rape(AACC,2n=38)in China.At the end of the 20th century,wild B.juncea was mainly distributed in the northwest of China,and now it has spreaded to the Yangtze River region and become an important weed which widely distributed in the wasteland and farmland.If the resistance genes of herbicide-resistance oilseed rape escape into wild B.juncea,wild B.juncea with herbicide resistant trait might produce new problems for weed control in the same herbicide resistant crop field.Therefore,study on introgression of herbicide-resistant gene from transgenic oilseed rape to wild B.juncea before transgenic oilseed rapes are released into the environment is necessary.Whether transgene could introgress into wild relatives is decided by transfer of resistant gene to progenies and fitness of hybrids or backcross generations.Many researches have reported on fitness of backcross generations between transgenic oilseed rape and wild or weed relatives.However,continuous tracking researches on inheritance of transgene in backcross generations and fitness of these backcross generations between transgenic herbicide-resistant oilseed rape and wild B.juncea in greenhouse and in field are lacking.The first,the second and the third progeny of the first backcross generation(BC1F2,BC1F3,and BC1F4),the first and the second progeny of the second backcross generation(BC2F2,BC2F3),the first progeny of the third backcross generation(BC3F2)of transgenic glyphosate-resistant oilseed rape(DS-Roughrider,Roundup Ready,event RT73)or glufosinate-resistant oilseed rape(Swallow,Liberty Link,event HCN92)and wild B.juncea were researched on inheritance of herbicide-resistant gene and fitness in greenhouse and in field in different densities and planting proportions.On the basis of previous studies,the fourth,the fifth of the first backcross generation(BC1F5,BC1F6),the third,the fourth of the second backcross generation(BC2F4,BC2F5),the second,the third progeny of the third backcross generation(BC3F3,BC3F4)of transgenic glufosinate-resistant oilseed rape and wild B.juncea were researched on inheritance of herbicide-resistant gene.Furthermore,the fitness of resistant BC1F4-5,BC2F3-4,BC3F2-3 in greenhouse and in field in different densities and planting proportions were researched.The main results are as follow:1.The emergence tates and inheritance of herbicide-resistant gene of BC1F5-6、BC2F4-5、BC3F3-4The fourth and the fifth progeny of the first backcross generation(BC1F5,BC1F6),the third and the fourth progeny of the second backcross generation(BC2F4,BC2F5),the second and the third progeny of the third backcross generation(BC3F3,BC3F4)between transgenic glufosinate-resistant oilseed rape and wild B.juncea were researched on emergence rates in greenhouse and inheritance of glufosiante-resistant gene.The results showed that emergence rates of all backcross generations were more than 90%,and had no significant differences with that of wild B.juncea.After selection by 700 g(a.i.)/ha glufosiante,the percentage of surviving plants in diferent backcross generation were as follow:BC1mF5 and BC1pF5,54.63%and 53.03%;BC2mF4 and BC2pF4,73.42%and 62.93%;BC3mF3 and BC3pF3,70.41%and 75.36%;BC1mF6 and BC1pF6,53.86%and 59.84%;BC2mF5 and BC2pF5,77.29%and 68.35%;BC3mF4 and BC3pF4 74.9%and 76.63%.The glufosinate transgene inheritance in all backcross generations did not follow the expected Mendelian segregation.The above results demonstrated that all backcross generations had similar emergence rates with wild B.juncea and glufosinate-resistant gene transferred to the next generations with more than 53%.The glufosinate-resistant plant percentages of-backcross generations did not increase with the increasing of-the self-pollination times significantly,especially in the progenies of BC1.2.Fitness of BC1F4-5.BC2F3-4 and BC3F2-3 in greenhouseThe composite fitness of the third and the f-ourth progeny of the first backcross generation(BC1F4.BC1F5),the second and the third progeny of the second backcross generation(BC2F3,BC2F4),the first and the second progeny of the third backcross generation(BC31F2,BC3F3)with resistant gene bewteen transgenic glufosinate-resistant oilsceed rape with wild B.juncea were researched in greenhouse.The results demonstrated that plant height,stem diameter,pollen viability,seed number/silique of BC1F4 and BC2F3 were significantly lower than that of wild B.juncea.Furthermore,the above-ground dry biomass of BC1F4 was also lower than that of wild B.juncea.The majortity fitness componets of BC3F3 were similar to that of wild B.juncea except for stem diameter.BC1F5 and BC2pF4 had lower plant height and stem diameter compared with wild B.juncea.BC1F5 also had lower above-ground dry biomass and BC1pF5 had lower seed number/silique compared with wild B.juncea.As theirs parents,the majortity componets of BC3F3 and BC2mF4 were similar to that of wild B.juncea except for stem diameter.Finally BC1F4,BC1pF5 and BC2pF3 had lower composite finess,but BClmF5,BC2mF3,BC2F4,BC3F2 and BC3F3 had similar composite fitness compared to wild B.juncea.The above results implied that the composite fitness of backcross generation increased with the increasing of backcross times and the self-pollination times.Furthermore,the composite fitness of backcross generations increased faster with wild B.juncea as maternal plants than as paternal plants.3.Fitness of BC1F4-5、BC2F3-4 and BC3F2-3 in fieldThe fitness components of BC1F4,BC1F5,BC2F3,BC2F4,BC3F2 and BC3F3 between glufosinate-resistan transgenic oilseed rape and wild Bjuncea in field under different densities and different planting proportions were measured.The survival ability of seeds of backcross generations over winter in the field was also investigated.The results showed that,in pure plots under low density(15 plants/plot),the composite fitness of BC1F4 and BC2F3 were significantly lower than that of wild B.juncea.But the composite fitness of BC3F2 was no significant difference with that of wild B.juncea.The composite fitness BC1F5,BC2F4 and BC3F3 were no significant differences with that of wild Bjuncea.In pure plots under high density(30 plants/plot),the composite fitness of BC1F4 and BC2F3 were lower than that of wild B.juncea and the composite fitness of BC3F2 was no significant difference with that of wild B.juncea.The composite fitness of BC1F5 and BC2F4 were lower than that of wild B.juncea and the composite fitness of BC3F3 was no significant difference with that of wild B.juncea.In mix plots,in low density under 4:1,3:2 propotions,the composite fitness of backcross generations was lower than that of wild B.juncea except for BC3mF3,which was fit as wild B.juncea.In low density and 1:1 propotions,the composite fitness of backcross generations was lower than that of wild B.juncea except for BC3mF2 and BC3mF3,which was fit as wild B.juncea.In 30 pant/plots,the composite fitness of all backcross generations was lower than that of wild B.juncea in three propotions.In 15 pant/plots,competition had a significant impact on fitness of BC3pF2、BC3pF3 and BC3mF2,and not a significant impact on on fitness of BC1F4,BC1F5,BC2F3,BC2F4 and BC3mF3.The planting proportion only had a significant impact on fitness of BC3mF2.In 30 pant/plots,competition had a significant impact on fitness of BC3F2 and BC3F3,and not a significant impact on on fitness of BC1F4,BC1F5,BC2F3 and BC2F4.The planting proportion had not a significant impact on fitness of all backcross generation.In pure plots,planting density had a significant impact on fitness of BC1F5 and BC2F4;In mix plots,in low density under 4:1,3:2 propotions,planting density had a significant impact on fitness of BC3mF3;In mix plots,in low density under 1:1 propotions,planting density had a significant impact on fitness of BC3mF2 and BC3mF3.Correlation analysis showed that it is a negative correlation between above-ground dry biomass/plant,silique number,and weight of seed/plant of wild B.juncea and all backcross generation and planting density.The results indicated that,more than 35%and 56%of seeds of BC1F5,BC2F4 and BC3F3 after buried for 11 months and more than 32%and 70%of seeds of BC1F6,BC2F5 and BC3F4 after buried for 9 months kept viability in soil at 3cm depth and 15cm depth,respectively,and seed viability was higher ini 5cm depth soil than that in 3cm depth soil.From the above results,although inheritance of glufosinate-resistance gene in all of progenies did not follow Mendelian segregation,glufosinate-resistant gene transferred to the next generations with more than 53%.In greenhouse,BC2mF3、BC3F2 and BClmF5、BC2F4、BC3F3 with glufosinate-resistance gene may have the similar survival ability with wild B.juncea,while the ability of other backcross progeny is still weaker then that of wild B.juncea.In field,BC3mF2 and BC3mF3 which have glufosinate-resistance gene may have the similar survival ability with wild B.juncea,while the ability of other backcross progeny is still weaker then that of wild B.juncea.The backcross generations seeds buried at 3cm and 15cm depth in soil kept seed vitality very well.These seeds had a potential to become volunteers in field.Therefore we should avoid to backcross between F1(glufosinate-resistance GM oilseed rape and wild B.juncea)and wild B.juncea again and to minimize seeds spread.of backcross generation in order to reduce ecological risk induced by glufosinate-resistance GM oilseed rape. |
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