Site and plant or soil niche drive the above- and below-ground perennial ryegrass (Lolium perenne) microbiota in established pastures in New Zealand

Aim: 

New Zealand’s primary-export driven economy relies on perennial ryegrass as the feed base for most livestock farms. Microbiota have been demonstrated to be critically important for many soil and plant functions, but the communities associated with perennial ryegrass in NZ are largely unknown. This study aimed to determine ryegrass microbiota across several farming sites (and soil types) and between plant and soil niches to determine to what extent they were drivers of community structure.  

Method: 

Forty plots of three-year-old perennial ryegrass plants were sampled from each of four sites across New Zealand. Samples were separated into below- (soil, rhizosphere soil, root) and above-ground (shoots and phyllosphere) niches (ie 800 subsamples). Microbial communities were determined by extracting DNA and analysing using 16S and ITS MiSeq amplicon sequencing. 

Results:

Ryegrass bacterial alpha diversity was strongly influenced by niche with rhizosphere being the most and phyllosphere the least diverse. Site had a significant effect on bacterial alpha diversity only for bulk soil and shoots. Fungal alpha diversity was significantly driven by both niche and site with bulk soil and rhizosphere being more diverse than shoots. Both bacterial and fungal beta diversity showed a clear separation between below- and above-ground communities. There were few microbial taxa shared across sites and niches.

Conclusions: 

This work is a first step in understanding the below- and above-ground microbial diversity of an important forage grass in NZ. It opens targeted approaches to manipulating microbiota for improved ryegrass persistence via plant breeding, microbial isolations, or soil amendments.