短小芽孢杆菌BX-4抗生素标记及定殖效果研究

Ampicillin-resistant Bacillus pumilus BX-4 and Its Colonization in the Tomato Rhizosphere

为研究短小芽孢杆菌BX-4在作物根际的定殖及防病效果，通过浓度梯度法用氨苄青霉素对其进行了抗性标记，并通过番茄盆栽试验研究了其在根际土壤中的定殖规律。结果表明，筛选出的突变体菌株BX-4＇能够耐受浓度为200 μg·mL^-1的氨苄青霉素，并且具有耐药和遗传双重稳定性；应用试验显示该突变体菌株能成功在番茄根际定殖，接种20 d后根际土壤中存活数量达到最高值1.34×10^8 cfu·g^-1干土，以后逐渐下降，到50 d时趋于稳定；筛选的突变体菌株对番茄青枯病具有明显的防治效果，防效达37.9%-50.9%。短小芽孢杆菌BX-4在作物根部的定殖规律为揭示其生防机理及应用该菌提供了科学根据。

Bacillus pumilus BX-4 was marked by the method of concentration grads with Ampicillin for studying its disease-controlling and colonization effects in the tomato rhizosphere, and the colonizing dynamics was also studied in pot experiment. The results indicated that the selected mutant BX-4＇can tolerate Ampicillin at a rate of 200 μg·mL^-1, meanwhile the mutant strain has the stabilities of Ampicillin resistance and heredity, and the growth and pH curve take the same tendency with the original strain BX-4, and the mutant strain has also kept the same resistance to Ralstonia solanacearum. The mutant strain can colonize in the tomato rhizosphere successfully, and the survival number reached the peak value 1.34×10^8 cfu·g^-1 dry soil after inoculation of 20 days, then descended gradually, and tended to be stable in 50 days. At the same time, the mutant strain had obvious disease-controlling effect on the tomato bacterial wilt, and the disease-controlling rate reached 37.9%-50.9%. With the decline of the mutant number in soil, the effect became lower. In addition, the strain DNA sequences were also measured, which testified that the mutant strain is Bacillus pumilus by contrasting with the GenBank data. The colonization of BX-4 in the rbizosphere affords scientific basis for its application and the further research on bio-controlling mechanism.