转Bt+CpTI基因棉花对根际土壤细菌及氨氧化细菌数量的影响

Effects of transgenic Bt + CpTI cotton on rhizosphere bacteria and ammonia oxidizing bacteria population

转基因棉花对根际土壤微生物的影响在转基因作物风险评估中具有重要意义。【目的】通过研究转基因棉花根际微生物群落变化来评估转基因棉花的生态风险。【方法】以转Bt+CpTI基因抗虫棉(SGK321)及非转基因亲本棉花石远321(SY321)根际土壤总细菌和氨氧化细菌为研究对象,分别在种植前和棉花的不同生长时期(蕾期、花期、铃期和絮期)取样。采用微滴数码PCR方法对土壤中总细菌16S rRNA和氨氧化细菌的功能基因amoA基因进行定量分析。【结果】结果发现两种棉花根际土壤中的总细菌数量随棉花生长的不同时期没有显著差异。但是对氨氧化细菌的定量结果表明随棉花不同生长时期,两种棉花根际土壤中的氨氧化细菌数量均发生显著变化,但变化趋势不同:在蕾期,SY321和SGK321根际土壤中的氨氧化细菌数量分别增加了4倍和2倍;在花期,SY321根际氨氧化细菌与蕾期相比显著降低至5.96×105copies/g dry soil,而SGK321根际氨氧化细菌则显著增加至1.25×106copies/g dry soil;在铃期,SY321根际氨氧化细菌显著增加至1.49×106copies/g dry soil,而SGK321根际土壤中氨氧化细菌数量没有发生显著变化;絮期两者均表现为降低,但差异显著。与非转基因棉花相比,转基因棉花根际土壤中的氨氧化细菌变化相对较为平缓。【结论】这表明氨氧化细菌数量既受棉花生长时期的影响,同时也受转基因棉花的影响,转基因棉花通过影响氨氧化细菌的数量减缓氨的转化速度,这在一定程度上有利于植物生长。

The effect of transgenic cotton on the rhizosphere bacteria can be important to the risk assessment for the genetically modified crops.［Objective］ We studied the rhizosphere microbial community with cultivating genetically modified cotton．［Methods］The effects of transgenic Bt ＋ CpTI Cotton （SGK321） and its receptor cotton （SY321） on rhizosphere total bacteria and ammonia oxidizing bacteria population size were studied by using droplet digital PCR．We collected rhizosphere soil before cotton planting and along with the cotton growth stage （squaring stage，flowering stage，belling stage and boll opening stage）．［Results］There was no significant change on the total bacterial population between the transgenic cotton and the receptor cotton along with the growth stage．However，the abundance of ammonia oxidizing bacteria （AOB） in both type of cottons showed significant difference between different growth stages，and the variation tendency was different．In squaring stage，the numbers of AOB in rhizosphere of SY321 and SGK321 increased 4 and 2 times，respectively． In flowering stage，AOB number in rhizosphere of SY321 significantly decreased to be 5.96×105 copies/g dry soil，however，that of SGK321 increased to be 1.25×106 copies/g dry soil．In belling stage，AOB number of SY321 greatly increased to be 1.49×106 copies/g dry soil，but no significant change was observed for AOB number of SGK321．In boll opening stage，both AOB number of SY321 and SGK321 clearly decreased and they were significantly different from each other．Compared to the non-genetically modified cotton，the change in abundance of ammonia oxidizing bacteria was slightly smooth in the transgenic cotton，［Conclusions］Not only the cotton growth stage but also the cotton type caused this difference． The transgenic cotton can slow down the speed of ammonia transformation through impacting the number of AOB，which is advantageous for plant growth．