Landa Blanca B, Mavrodi Olga V, Schroeder Kurtis L, Allende-Molar Raul, Weller David M
Department of Plant Pathology, Washington State University, Pullman, WA 99164-6430, USA.
FEMS Microbiol Ecol. 2006 Mar;55(3):351-68. doi: 10.1111/j.1574-6941.2005.00038.x.
Fluorescent Pseudomonas spp. producing the antibiotic 2,4-diacetylphloroglucinol (2,4-DAPG) play a key role in the suppressiveness of some soils to take-all of wheat and other diseases caused by soilborne pathogens. Soils from side-by-side fields on the campus of North Dakota State University, Fargo, USA, which have undergone continuous wheat, continuous flax or crop rotation for over 100 years, were assayed for the presence of 2,4-DAPG producers. Flax and wheat monoculture, but not crop rotation, enriched for 2,4-DAPG producers, and population sizes of log 5.0 CFU g root(-1) or higher were detected in the rhizospheres of wheat and flax grown in the two monoculture soils. The composition of the genotypes enriched by the two crops differed. Four BOX-PCR genotypes (D, F, G, and J) and a new genotype (T) were detected among the 2,4-DAPG producers in the continuous flax soil, with F- and J-genotype isolates dominating (41 and 39% of the total, respectively). In contrast, two genotypes (D and I) were detected in the soil with continuous wheat, with D-genotype isolates comprising 77% of the total. In the crop-rotation soil, populations of 2,4-DAPG producers generally were below the detection limit, and only one genotype (J) was detected. Under growth-chamber and field conditions, D and I genotypes (enriched by wheat monoculture) colonized the wheat rhizosphere significantly better than isolates of other genotypes, while a J-genotype isolate colonized wheat and flax rhizospheres to the same extent. This study suggests that, over many years of monoculture, the crop species grown in a field enriches for genotypes of 2,4-DAPG producers from the reservoir of genotypes naturally present in the soil that are especially adapted to colonizing the rhizosphere of the crop grown.
产生抗生素2,4 - 二乙酰基间苯三酚（2,4 - DAPG）的荧光假单胞菌属在某些土壤对小麦全蚀病及其他土传病原菌引起的病害的抑制作用中起关键作用。对美国北达科他州立大学法戈分校校园内并排田地的土壤进行了检测，这些土壤已经连续种植小麦、连续种植亚麻或轮作超过100年，以检测2,4 - DAPG产生菌的存在情况。亚麻和小麦单作而非轮作富集了2,4 - DAPG产生菌，在两种单作土壤中种植的小麦和亚麻的根际检测到了对数5.0 CFU g根（-1）或更高的种群数量。两种作物富集的基因型组成不同。在连续种植亚麻的土壤中，在2,4 - DAPG产生菌中检测到了四种BOX - PCR基因型（D、F、G和J）以及一种新基因型（T），其中F基因型和J基因型分离株占主导（分别占总数的41%和39%）。相比之下，在连续种植小麦的土壤中检测到了两种基因型（D和I），其中D基因型分离株占总数的77%。在轮作土壤中，2,4 - DAPG产生菌的种群数量通常低于检测限，仅检测到一种基因型（J）。在生长室和田间条件下，D和I基因型（由小麦单作富集）在小麦根际的定殖明显优于其他基因型的分离株，而一种J基因型分离株在小麦和亚麻根际的定殖程度相同。这项研究表明，经过多年的单作，田间种植的作物品种会从土壤中自然存在的基因型库中富集特别适应在该作物根际定殖的2,4 - DAPG产生菌的基因型。
