钩状木霉与枯草芽孢杆菌在核桃根际土壤中的定殖研究

  目的  植物病害生防菌在植物根际土壤中的定殖情况是影响其发挥生防作用的重要因素之一。近年来，由核桃炭疽病菌引起的核桃炭疽病对云南省核桃产业的发展产生了较为严重的危害，已成为该省核桃产业发展的重要制约因素。前期，通过对大理州漾濞县光明村核桃根际土壤生防菌的筛选工作，获得了具有重要生防潜力的钩状木霉YB-4-15和枯草芽孢杆菌yb33。为了推广上述生防菌株，需首先明确上述菌株在核桃根际土中的定殖情况。  方法  本研究利用不同浓度钩状木霉孢子悬浮液对无菌的核桃根际土壤进行处理，采用定期测定根际土壤中上述生防菌的定殖量。  结果  通过长达一个月的定殖试验，发现钩状木霉在土壤中定殖后的最大量为5 × 104 cfu/g，最小为2 × 104 cfu/g；同时，利用抗利福平枯草芽孢杆菌yb33-Rif在无菌土壤中定殖的最大量为1.08 × 108 cfu/g，最小为7.07 × 106 cfu/g，而在核桃根际土壤中的定殖能力明显低于无菌土，其最大量为7.53 × 106 cfu/g，最小为1.03 × 106 cfu/g。利用上述生防菌钩状木霉YB-4-15孢子和枯草芽孢杆菌yb33菌体浇灌在核桃、桂花、香樟以及石楠等不同根际土壤试验，发现二者在核桃根际土壤中定殖良好。  结论  该研究为这两株生防菌的田间应用提供了理论基础。 

Colonization of Trichoderma hamatum and Bacillus subtilis in rhizosphere soil of walnut

  Objective  The colonization of plant disease biocontrol agents in plant rhizosphere soil is one of the important factors affecting its biocontrol effect. In recent years, walnut anthracnose has caused serious harm to the development of walnut industry in Yunnan Province of southwestern China, and it has posed a serious threat to the development of walnut industry in the growing areas. In the early stage, Trichoderma hamatum YB-4-15 and Bacillus subtilis yb33, which are important biocontrol agents, were obtained indoors by screening biocontrol of anthracnose on walnut in rhizosphere soil of Guangming Village, Yangbi County, Dali City. To better promote the above biocontrol agents, the colonization of the above strains in the rhizosphere of walnuts should be firstly considered.   Method  Trichoderma spore suspensions of different concentrations were applied to sterilized rhizosphere of walnuts.   Result  The colonization amount of the two biocontrol agents in rhizosphere soil was regularly measured, and it was found that after one month of mixing the biocontrol agents to the rhizosphere soil, the colonization amount of T. hamatum was 2 × 104 cfu/g at lowest level to 5 × 104 cfu/g at maximum level. At the same time, the rifampicin-resistant B. subtilis yb33-Rif was used to determine the colonization ability in sterilized soil and field soil, the colonization amount of tested bacteria ranged from 7.07 × 106 to 1.08 × 108 cfu/g, significantly lower in field soil than in sterilized soil, ranging from 1.03 × 106 cfu/g at lowest level to 7.53 × 106 cfu/g at maximum level. In addition, the two tested biocontrol agents were mixed in the rhizosphere soils of walnut, osmanthus, camphor and heather, and it was found that the two biocontrol agents were found to grow well in walnut rhizosphere soil.  Conclusion  The current study lays a solid base for future application of the two biocontrol agents in walnut fields.