Impact of biochar application to soil on the root-associated bacterial community structure of fully developed greenhouse pepper plants

Impact of biochar application to soil on the root-associated bacterial community structure of fully developed greenhouse pepper plants.
Max Kolton, Yael Meller Harel, Zohar Pasternak, Ellen R. Graber, Yigal Elad, and Eddie Cytryn
AEM Accepts, published online ahead of print on 27 May 2011
Appl. Environ. Microbiol. doi:10.1128/AEM.00148-11

Abstract: Adding biochar to soil has environmental and agricultural potentialdue to its long-term carbon sequestration capacity and its abilityto improve crop productivity. Recent studies have demonstratedthat soil-applied biochar promotes systemic resistance of plantsto several prominent foliar pathogens. One potential mechanismfor this phenomenon is root-associated microbial elicitors whosepresence is somehow augmented in the biochar-amended soils.The objective of this study was to assess the effect of biocharamendment on the root-associated bacterial community compositionof mature sweet pepper (Capsicum annuum L.) plants. Molecularfingerprinting (DGGE and T-RFLP) of 16S rRNA gene fragmentsshowed a clear differentiation between the root-associated bacterialcommunity structures of biochar-amended and control plants.Pyrosequencing of 16S rRNA amplicons from the rhizoplane ofboth treatments generated a total of 20,142 sequences, 92-95%of which were affiliated with the Proteobacteria, Bacterioidetes,Actinobacteria, and Firmicutes phyla. The relative abundanceof members of the Bacterioidetes phylum increased from 12 to30% as a result of biochar amendment, while that of the Proteobacteriadecreased from 71 to 47%. The Bacteroidetes-affiliated Flavobacteriumwas the strongest biochar-induced genus. The relative abundanceof this group increased from 4.2% of total root-associated operationaltaxonomic units (OTUs) in control samples to 19.6% in biocharamended samples. Additional biochar-induced genera includedchitin and cellulose degraders (Chitinophaga and Cellvibrio,respectively) and aromatic compound degraders (Hydrogenophagaand Dechloromonas). We hypothesize that these biochar augmentedgenera may be at least partially responsible for the beneficialeffect of biochar amendment on plant growth and viability.

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