The importance of telluric microorganisms linked together by trophic exchanges with plants, that sustain all ecosystems through primary production, is known. However, the role of soil microbial diversity for primary production remains controversial. A diversity decreasing was achieved, by inoculating a sterilized soil with serial dilutions of a suspension from the same non-sterilized soil, to determine the consequences of microbial diversity erosion on the growth and fitness of three plant species more or less dependent on symbionts, Medicago truncatula, Brachypodium distachyon and Arabidopsis thaliana. The results showed that the impact of microbial diversity decreasing on plants depends on their reliance on symbionts. On the whole, M. truncatula was negatively affected by erosion, B. distachyon was positively affected and there was no significant effect on A. thaliana. These results are of interest to predict the consequences of soil microbial diversity erosion, on crop plants productivity under low nutrient inputs, according to microbial communities and symbiotic interactions.