Changes in rhizosphere microbial diversity and composition due to NaCl addition to the soil modify the outcome of maize-weed interactions

Abstract

Increases in salt concentration in the soil may occur as a consequence of manure and fertilizer application. We have hypothesized that changes in the structure of rizhosphere microbial communities, caused by increased salt, lead to distinct outcomes of crop-weed ecological interactions. Here, we have evaluated the outcomes of Zea mays-weed coexistence as a function of changes in the structure of the rhizosphere microbial communities due to NaCl addition to the soil. The growth of two weed species, Amaranthus viridis and Bidens pilosa, and the crop Z. mays, was evaluated in the greenhouse under two management conditions, monoculture and plant coexistence, with and without NaCl addition to the soil. Total DNA from the microbial populations in the rhizosphere soil was extracted, followed by PCR amplification and sequencing using the Illumina MiSeq platform. NaCl addition caused significant changes in bacterial diversity and in the structure and composition of bacterial and fungal taxa. These changes were associated to the outcome of maize-weed interactions. The rhizosphere soil microbiota was more sensitive to NaCl addition than the plants. For the interaction between maize and B. pilosa, the ecological interaction changed from competition to facilitation after NaCl addition. This could be attributed to the changes in the rhizosphere microbial community structure rather than to increases in soil electrical conductivity (EC) since this variable did not affect plant growth. Thus, the influence of rhizosphere microbial communities on plant-plant interactions should be taken into account for the development of integrated weed management practices.