Commentary: Agroforestry leads to shifts within the gammaproteobacterial microbiome of banana plants cultivated in Central America

Citation: Pirttilä AM (2016) Commentary: Agroforestry leads to shifts within the gammaproteobacterial microbiome of banana plants cultivated in Central America. Front. Microbiol. 7:656. The microbiomes of organisms are fast becoming thoroughly studied by the development of next-generation sequencing techniques. As hundreds of strains can be identified within hours, the research on microbial community structures and their shifts under varying conditions is a current trend. And rightly so, as microbiomes are recognized as a key factor behind the health of an organism—whether be it human, or plant. Köberl et al. (2015) studied the gammaproteobacterial microbiome of banana in response to geographical and agricultural factors, and discovered high numbers of Pseudomonadales, Enterobacteriales, Xanthomonadales, and Legionellales, and an exceptionally high richness of gammaproteobacteria as endophytes in banana. Endophytes, microbes living inside plant tissue without eliciting symptoms (Petrini, 1986), are shown increasingly important for the adaptation and fitness of the host. Members of this microbiome subgroup can protect the host from environmental stresses, induce plant resistance, and promote plant growth (Rosenblueth and Martinez-Romero, 2006; Hardoim et al., 2015). Köberl et al. found the banana gammaproteobacterial microbiome highly stable especially in the endophytic niche. Using profile-clustering network analyses, they however saw differences in the communities between treatments. The greatest differences were observed in the rhizospheric communities between the geographical sites, Nicaragua and Costa Rica. Moderate, but important changes were observed within the epiphytic and endophytic microbiomes between the agroforestry systems, i.e., banana grown with and without green manure, which is used for nitrogen fertilization by legumes growing next to the crop plant. Specifically interesting were the stability of banana microbiome and the changes caused by the neighboring plants in each agroforestry system, which I discuss here. Our most popular natural treat, banana (Musa spp.), is a clonally propagated plant, similar to many important food crops (McKey et al., 2010). Clonal propagation produces plant individuals identical by their genetic heritage and, for example, cultivated banana has almost completely lost the capacity for production of viable seeds. Therefore, banana plants are produced by clonal propagation from suckers, or through micropropagation (Singh et al., 2011). This is especially important when considering endophytic microbiomes of banana, for two reasons. First, whereas plant seeds can carry members of the microbiome to the next generation, only very few are transmitted through micropropagation (Koskimäki et al., 2010; Quambusch et al., 2014). The meristems that are used for micropropagation often host lower numbers …