Intercropping with Chinese leek decreasedMeloidogyne javanicapopulation and shifted microbial community structure in Sacha Inchi plantation

Abstract

The root-knot nematode, Meloidogyne javanica, is a major problem for the production of Sacha Inchi plants. We examined the effects of strip intercropping of Sacha Inchi/Chinese leek of 3–4 years on the seasonal dynamics of plant and soil traits in tropical China. Results indicated that in the intercropping system, a partially temporal divergence of belowground resource acquisition via niche separation occurred throughout the growing seasons, besides a complete spatially-separated plant height between the two crops. Compared with Sacha Inchi monoculture, the increased seed yield per unit area in the intercropping system was mainly attributed to the higher plant survival rate, rather than the enhanced plant traits of healthy plants. Intercropping greatly suppressed M. javanica populations only in the wet season, compared with monoculture; which may be associated with the combined effects of the direct allelopathy and indigenous microbe induced-suppressiveness. Intercropping did not affect microbial richness and α-diversity in the rhizosphere, except for the decreased fungal richness. Both bacterial and fungal composition and structure were diverged between monoculture v. intercropping system. The relative abundances of the dominant bacterial genera (Bacillus, Gaiellales, Lactococcus, Massilia and Lysobacter, etc.) differed significantly between the two cropping systems. For fungi, intercropping decreased the relative abundances of Fusarium and Gibberella, but increased those of Nectriaceae_unclassified, Chaetomiaceae, Humicola and Mortierella. Overall, Sacha Inchi/Chinese leek intercropping suppressed M. javanica populations and shifted microbial compositions (especially decreased pathogen-containing Fusarium). The increased yield and economic returns in this intercropping system provide valid information for the effective agricultural management.