Abstract
Background and Aims: In China, excessive fertilization has resulted in phosphorus (P) accumulation in most greenhouse soils. Intercropping can improve the efficiency of nutrient utilization in crop production. In this study, pot experiments were performed to investigate the effects of intercropping with potato onion (Allium cepa L. var. aggregatum G. Don) on tomato (Solanum lycopersicum L.) seedlings growth and P uptake, the diversity of rhizosphere phosphobacteria and alkaline phosphatase (ALP) genes in phosphorus-rich soil.Methods: The experiment included three treatments, namely tomato monoculture (TM), potato onion monoculture (OM), and tomato/potato onion intercropping (TI-tomato intercropping and OI-potato onion intercropping). The growth and P uptake of tomato and potato onion seedlings were evaluated. The dilution plating method was used to determine the population of phosphate-solubilizing bacteria (PSB) and phosphate-mineralizing bacteria (PMB). The genomic DNAs of PSB and PMB in the rhizosphere of tomato and potato onions were extracted and purified, and then, with the primer set of 338f /518r, the PCR amplification of partial bacterial 16S rDNA sequence was performed and sequenced to determine the diversities of PSB and PMB. After extracting the total genomic DNAs from the rhizosphere, the copy numbers and diversities of ALP genes were investigated using real-time PCR and PCR-DGGE, respectively.Results: Intercropping with potato onion promoted the growth and P uptake of tomato seedlings, but inhibited those of potato onion. After 37 days of transplanting, compared to the rhizosphere of TM, the soil pH increased, while the electrolytic conductivity and Olsen P content decreased (p < 0.05) in the rhizosphere of TI. The populations and diversities of PSB, PMB, and ALP genes increased significantly in the rhizosphere of TI, compared to the rhizosphere of TM.Conclusion: The results indicated that intercropping with potato onion promoted the growth and P uptake of tomato in phosphorus-rich soil and affected the community structure and function of phosphobacteria in tomato rhizosphere. Intercropping with potato onion also improved soil quality by lowering levels of soil acidification and salinization.
Highlights
Phosphorus (P) is an important mineral nutrient for plant growth
The aims of this study are to evaluate the effects of tomato/potato onion intercropping on the growth and P uptake of tomato and potato onion and investigate the changes in the structure and composition of phosphate-solubilizing bacteria (PSB) and phosphatemineralizing bacteria (PMB) in the rhizosphere of tomato and potato onion, with the changes of alkaline phosphatase (ALP) gene copy numbers and community structure of ALP geneharboring bacteria in the rhizosphere of tomato and potato onion determined
The root dry weight (DW), shoot DW, and P uptake in the shoot of tomato seedling at 37 days after transplanting (DAT) were significantly higher in intercropping system than those in tomato monoculture (TM) system (Table 1)
Summary
Phosphorus (P) is an important mineral nutrient for plant growth. Excessive fertilizer application increased soil electrolytic conductivity (Ec) and decreased pH, resulting in secondary salinization and degeneration of soils (Shi et al, 2009), which, in turn, would deteriorate soil nutrient availability, plant growth, and uptake ability (He, 2004; Ghehsareh and Samadi, 2012). Since PSB and PMB could increase P availability of soil, it is significant to study the roles of them in intercropping. Little information is known about how intercropping influences the communities composition of PSB and PMB, as well as P availability in phosphorus-rich soil. In China, excessive fertilization has resulted in phosphorus (P) accumulation in most greenhouse soils. Don) on tomato (Solanum lycopersicum L.) seedlings growth and P uptake, the diversity of rhizosphere phosphobacteria and alkaline phosphatase (ALP) genes in phosphorus-rich soil
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