Department of Plant Pathology, University of California at Berkeley, Berkeley, California 94720.
Appl Environ Microbiol. 1993 Jul;59(7):2064-70. doi: 10.1128/aem.59.7.2064-2070.1993.
Sodium salicylate (1,000 mug/ml) was delivered through a drip irrigation system to agricultural field soils planted to tomato and infested with Pseudomonas putida PpG7, the host of the salicylate catabolic plasmid NAH7. In nonfumigated soils infested with approximately 10 CFU of PpG7 per g in the top 30 cm, population densities were increased up to 112-fold within 14 days of the initial application of salicylate compared with the densities in the respective nonamended soils. Mean season-long population densities of PpG7 in the top 30 cm of soil were significantly increased (P < 0.01) from 216 CFU/g in nonamended soils to 1,370 CFU/g in salicylate-amended soils. In the respective rhizosphere soils, mean population densities of PpG7 were significantly increased (P < 0.01) from 92 to 2,066 CFU/cm of root. Soil fumigation interacted (P < 0.01) with salicylate amendment and further increased the mean population densities of PpG7 in nonrhizosphere soil by an additional 5,689 CFU/g of soil. This fumigation effect was not detected in rhizosphere soils. The effect of salicylate in increasing population densities of PpG7 in soil also was affected by inoculum level, field site, and soil depth. Proportionate differences were greater in soils infested with approximately 10 CFU of PpG7 per g than in comparable soils infested with 10 CFU/g. In low-inoculum soils, increases from salicylate amendments were 26- and 29-fold in rhizosphere and nonrhizosphere soils, respectively, and in high-inoculum soils, the respective increases were 5.6- and 5-fold. No increases of fungi able to utilize salicylate were detected in soils amended with salicylate. However, soil fumigation with metham-sodium significantly reduced (P < 0.01) population densities of fungal salicylate utilizers in rhizosphere and nonrhizosphere soils.
水杨酸（1000 微克/毫升）通过滴灌系统输送到种植番茄并感染了假单胞菌 PpG7 的农田土壤中，PpG7 是水杨酸代谢质粒 NAH7 的宿主。在未熏蒸的土壤中，顶部 30 厘米处每克约有 10 CFU 的 PpG7，与相应的未添加土壤相比，在最初施加水杨酸后的 14 天内，种群密度增加了高达 112 倍。在顶部 30 厘米的土壤中，PpG7 的平均季节种群密度显著增加（P < 0.01），从未添加土壤中的 216 CFU/g 增加到添加水杨酸的土壤中的 1370 CFU/g。在相应的根际土壤中，PpG7 的平均种群密度显著增加（P < 0.01），从 92 增加到根的 2066 CFU/cm。土壤熏蒸与水杨酸添加相互作用（P < 0.01），并进一步使非根际土壤中 PpG7 的平均种群密度增加了另外的 5689 CFU/g。在根际土壤中未检测到这种熏蒸效应。水杨酸在增加土壤中 PpG7 种群密度方面的作用也受到接种水平、田间地点和土壤深度的影响。与可比的每克感染 10 CFU 的土壤相比，在感染约 10 CFU/g 的土壤中，比例差异更大。在低接种水平的土壤中，根际和非根际土壤中水杨酸添加物的增加分别为 26 倍和 29 倍，而在高接种水平的土壤中，相应的增加分别为 5.6 倍和 5 倍。在添加水杨酸的土壤中未检测到能够利用水杨酸的真菌的增加。然而，用甲硫威进行土壤熏蒸显著降低了根际和非根际土壤中真菌水杨酸利用者的种群密度（P < 0.01）。
