Effects of intercropping on rhizosphere soil microorganisms and root exudates of Lanzhou lily(Lilium davidii var.unicolor)

摘要

Both yield and quality of Lanzhou lily(Lilium davidii var.unicolor)are seriously affected by continuous cropping.We attempted to understand the effects of intercropping on the obstacles associated with continuous cropping of Lanzhou lily(Lilium davidii var.unicolor).The changes of rhizosphere microbial biomass and diversity in interplanting and monoculturing systems were studied by using the Illumina HiSeq sequencing technique.The contents and composition of lily root exudates were measured by gas chromatography–mass spectrometer(GC–MS).The intercropping results of Lanzhou lily showed:(1)There was no difference in the composition of the rhizosphere soil microbes at the phylum level,but the relative abundance of the microbes decreased;and the relative abundance of harmful fungi such as Fusarium sp.increased.The relative abundance of Pleosporales sp.and other beneficial bacteria were reduced.After OTU(operational taxonomic unit)clustering,there were some beneficial bacteria,such as Chaetomium sp.,in the lily rhizosphere soil in the interplanting system that had not existed in the single-cropping system.We did not find harmful bacteria that had existed in the single-cropping systm in the rhizosphere soil of interplanting system.The above results indicated that the changes of relative abundance of soil fungi and bacteria in lily rhizosphere soil was not conducive to improving the ecological structure of rhizosphere soil microbes.At the same time,the microbial composition change is very complex—beneficial and yet inadequate at the same time.(2)Root exudates provide a matrix for the growth of microorganisms.Combined with the detection of root exudates,the decrease in the composition of the root exudates of the lily was probably the reason for the decrease of the relative abundance of microbes after intercropping.At the same time,the decrease of the relative content of phenolic compounds,which inhibit the growth of microorganisms,did not increase the relative content of rhizosphere soil microorganisms.Changes in amino acids and total sugars may be responsible for the growth of Fusarium sp..The results showed that the intercropping pattern did not noticeably alleviate the obstacle to continuous cropping of Lanzhou lily,and the change of microbial biomass and diversity was even unfavorable.However,the emergence of some beneficial bacteria,the disappearance of harmful fungi,and other changes with intercropping are in favor of alleviation of obstacles to continuous cropping of Lanzhou lily.