LuxAB标记的N2106-L在小麦根圈的定植动态

目的研究小麦PGPR（植物根际促生菌）菌株的个体生态学及其在小麦根圈的定植动态。方法采用三亲本杂交法将发光酶基因luxAB转人具有固氮能力的小麦根际促生菌Azotobacter N2106菌株中，获得标记菌株N2106-L，将标记菌株接种到灭菌和非灭菌的黄褐土、红壤和黄潮土中研究其存活状况，采用根盒试验追踪标记菌株在小麦根圈的定植动态。结果标记菌株N2106-L具有发光活性和对km、str、tet三种抗生素的抗性，且具有较好的遗传稳定性。N2106-L在灭菌土壤中的数量稍高于非灭菌土壤；在3种土壤中的数量依次为：黄褐土〉黄潮土〉红壤。N2106-L在小麦根表定植密度大于根际定植密度；在小麦根际，小麦播种10d时标记菌株在0-2cm深度根际土壤定植达到最大值（2．17±0．25）×10^6CFU／g土，20d时在2-4cm深度的根际土壤中达到最高定植水平（3．92±0．47）×10^5CFU／g土；在小麦根表，标记菌株在小麦播种10d时在所有深度的根段均达到最高定植水平，0-2cm根段定植密度为（3．60±0．60）×10^6CFU／g鲜根，12cm以下根段达到（2．78±0．56）×10^4CFU／g鲜根。结论标记菌株随着根的伸长不断向根尖方向扩散，且较为稳定地在小麦根圈定植，研究结果为小麦PGPR菌株的应用提供了可靠实验数据。

Colonization dynamics of LuxAB gene-marked N2106-L in wheat rhizosphere

Objective To study the antecology of wheat PGPR（ plant growth-promoting rhizobacteria） and its colonization dynamics in wheat rhizosphere. Method LuxAB gene was transfered into Azotobacter N2106 strain by the tri-parent conjugation method to obtain the strain N2106-L labeled with/uxAB. The survival of the strain N2106-L in sterilized and non-sterilized yellow cinnamon soil （YC） ,yellow fluovoaquic soil （YF） ,and red soil （RS） were studied after inoculation into the soils. Rhizoboxes were used to trace the colonization dynamics of the strain around wheat root. Result The labeled strain N2106-L had a high luminescence activity and resistance to km,str and tet,and was genetically stable. Strain N2106- L in these three sterilized soils were higher than those in non-sterilized soils, and decreased in the order of YC 〉 YF 〉 RS. The colonization density of N2106-L on wheat rhizoplane was higher than in wheat rhizosphere. In rhizosphere soil, the colonization density reached to maximum （2.17±0.25） × 10 ^6CFU/g at the depths of 0 -2 cm after wheat grew for 10 days, and （ 3.92 ± 0.47 ） × 10^5 CFU/g at the depths of 2 - 4 cm after grew for 20 days. On wheat rhizoplane the colonization density of all root segments reached the highest level on day 10,with （3.60 ±0.60） × 10^6CFU/g fresh root on the surface of 0 ~ 2 cm segment and （2.78 ± 0.56） × 104CFU/g fresh root on that of segments deeper than 12 cm. Conclusion The labeled strain could proliferate continuously with the growth of wheat roots and stably colonized in wheat rhizosphere. The resuits orovided credible data for the study and application of wheat PGPR strains.