2 research outputs found
Bacterial Communities in the Rhizosphere of Amilaceous Maize (Zea mays L.) as Assessed by Pyrosequencing
Maize (Zea mays L.) is the staple diet of the native peasants in the Quechua region of the
Peruvian Andes who continue growing it in small plots called chacras following ancestral
traditions. The abundance and structure of bacterial communities associated with the
roots of amilaceous maize has not been studied in Andean chacras. Accordingly, the
main objective of this study was to describe the rhizospheric bacterial diversity of
amilaceous maize grown either in the presence or the absence of bur clover cultivated
in soils from the Quechua maize belt. Three 16S rRNA gene libraries, one corresponding
to sequences of bacteria from bulk soil of a chacra maintained under fallow conditions,
the second from the rhizosphere of maize-cultivated soils, and the third prepared from
rhizospheric soil of maize cultivated in intercropping with bur clover were examined using
pyrosequencing tags spanning the V4 and V5 hypervariable regions of the gene. A total
of 26031 sequences were found that grouped into 5955 distinct operational taxonomic
units which distributed in 309 genera. The numbers of OTUs in the libraries from the
maize-cultivated soils were significantly higher than those found in the libraries from bulk
soil. One hundred ninety seven genera were found in the bulk soil library and 234 and
203 were in those from the maize and maize/bur clover-cultivated soils. Sixteen out of
the 309 genera had a relative abundance higher than 0.5% and the were (in decreasing
order of abundance) Gp4, Gp6, Flavobacterium, Subdivision3 genera incertae sedis
of the Verrucomicrobia phylum, Gemmatimonas, Dechloromonas, Ohtaekwangia,
Rhodoferax, Gaiella, Opitutus, Gp7, Spartobacteria genera incertae sedis, Terrimonas,
Gp5, Steroidobacter and Parcubacteria genera incertae sedis. Genera Gp4 and Gp6
of the Acidobacteria, Gemmatimonas and Rhodoferax were the most abundant in bulk
soil, whereas Flavobacterium, Dechloromonas and Ohtaekwangia were the main genera
in the rhizosphere of maize intercropped with bur clover, and Gp4, Subdivision3 genera
incertae sedis of phylum Verrucomicrobia, Gp6 and Rhodoferax were the main genera
in the rhizosphere of maize plants. Taken together, our results suggest that bur clover
produces specific changes in rhizospheric bacterial diversity of amilaceous maize plants.Peer reviewe
Maize endophytic bacterial diversity as affected by soil cultivation history
The bacterial endophytic communities residing within roots of maize (Zea mays L.) plants cultivated by a sustainable management in soils from the Quechua maize belt (Peruvian Andes) were examined using tags pyrosequencing spanning the V4 and V5 hypervariable regions of the 16S rRNA. Across four replicate libraries, two corresponding to sequences of endophytic bacteria from long time maize-cultivated soils and the other two obtained from fallow soils, 793 bacterial sequences were found that grouped into 188 bacterial operational taxonomic units (OTUs, 97% genetic similarity). The numbers of OTUs in the libraries from the maize-cultivated soils were significantly higher than those found in the libraries from fallow soils. A mean of 30 genera were found in the fallow soil libraries and 47 were in those from the maize-cultivated soils. Both alpha and beta diversity indexes showed clear differences between bacterial endophytic populations from plants with different soil cultivation history and that the soils cultivated for long time requires a higher diversity of endophytes. The number of sequences corresponding to main genera Sphingomonas, Herbaspirillum, Bradyrhizobium and Methylophilus in the maize-cultivated libraries were statistically more abundant than those from the fallow soils. Sequences of genera Dyella and Sreptococcus were significantly more abundant in the libraries from the fallow soils. Relative abundance of genera Burkholderia, candidatus Glomeribacter, Staphylococcus, Variovorax, Bacillus and Chitinophaga were similar among libraries. A canonical correspondence analysis of the relative abundance of the main genera showed that the four libraries distributed in two clearly separated groups. Our results suggest that cultivation history is an important driver of endophytic colonization of maize and that after a long time of cultivation of the soil the maize plants need to increase the richness of the bacterial endophytes communities.This study was supported by ERDF-cofinanced grant PE2012-AGR1968 from Consejería de Economía, Innovación y Ciencia (Junta de Andalucía, Spain) and the CSIC-sponsored I-COOP Agrofood project 2014CD0013.Peer Reviewe