Schreiter Susanne, Babin Doreen, Smalla Kornelia, Grosch Rita
Institute for Epidemiology and Pathogen Diagnostics, Federal Research Centre for Cultivated Plants, Julius Kühn-Institut (JKI), Braunschweig, Germany.
Department Plant-Microbe Systems, Leibniz Institute of Vegetable and Ornamental Crops, Großbeeren, Germany.
Front Microbiol. 2018 Feb 1;9:97. doi: 10.3389/fmicb.2018.00097. eCollection 2018.
Biocontrol inoculants often show inconsistency in their efficacy at field scale and the reason for this remains often unclear. A high rhizosphere competence of inoculant strains is assumed to be a key factor for successful biocontrol effects as the biocontrol strain has to compete with the indigenous microbial community in the rhizosphere. It is known that many factors, among them plant species and soil type shape the rhizosphere microbial community composition. However, microbial community composition in the rhizosphere can also be influenced by the presence of a pathogen. We hypothesized that plant species, soil type, and a pathogen affect the rhizosphere competence of a biocontrol strain and its biocontrol effect against a soil-borne pathogen. To test the hypothesis, we used an experimental plot system with three soil types (diluvial sand, alluvial loam, loess loam) kept under similar agricultural management at the same field site for 12 years. We investigate the rhizosphere competence of sp. RU47 in two plant species (potato and lettuce) and its biocontrol effect against Rhizoctonia diseases. The colonization density of a rifampicin resistant mutant of RU47 in the rhizosphere of both crops was evaluated by plate counts. Bacterial community compositions were analyzed by denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments amplified from total community DNA. The inoculant RU47 was able to colonize the rhizosphere of both model crops in a sufficient density and to reduce disease severity of black scurf on potato and bottom rot on lettuce in all three soils. DGGE indicated that RU47 affected the bacterial community composition stronger in the rhizosphere of lettuce than in the potato rhizosphere. In contrast, the effect of the pathogen on the bacterial community was much stronger in the rhizosphere of potato than in the lettuce rhizosphere. A significant effect of RU47 on the -specific fingerprints of the rhizosphere was only observed in lettuce in alluvial soil. The soil type and plant species independent biocontrol effects of RU47 and its minor influence on the indigenous bacterial community composition might be important criteria for the registration and use of RU47 as biocontrol strain.
生物防治接种剂在田间规模上的功效往往不一致，其原因通常仍不清楚。接种菌株的高根际竞争力被认为是成功实现生物防治效果的关键因素，因为生物防治菌株必须与根际中的本土微生物群落竞争。已知许多因素，包括植物种类和土壤类型，塑造了根际微生物群落组成。然而，根际微生物群落组成也可能受到病原体存在的影响。我们假设植物种类、土壤类型和病原体影响生物防治菌株的根际竞争力及其对土传病原体的生物防治效果。为了验证这一假设，我们使用了一个试验小区系统，其中三种土壤类型（洪积砂、冲积壤土、黄土壤土）在同一田地以相似的农业管理方式保持了12年。我们研究了RU47菌株在两种植物（马铃薯和生菜）中的根际竞争力及其对丝核菌病害的生物防治效果。通过平板计数评估了RU47的利福平抗性突变体在两种作物根际中的定殖密度。通过对从总群落DNA扩增的16S rRNA基因片段进行变性梯度凝胶电泳（DGGE）分析细菌群落组成。接种剂RU47能够在足够的密度下定殖于两种模式作物的根际，并在所有三种土壤中降低马铃薯黑胫病和生菜根腐病的病害严重程度。DGGE表明，RU47对生菜根际细菌群落组成的影响比对马铃薯根际的影响更强。相比之下，病原体对马铃薯根际细菌群落的影响比对生菜根际的影响要强得多。仅在冲积土中的生菜中观察到RU47对根际特异性指纹图谱有显著影响。RU47的土壤类型和植物种类独立的生物防治效果及其对本土细菌群落组成的微小影响可能是将RU47登记为生物防治菌株并加以使用的重要标准。
