Abstract
The influence of wheat (modern wheat, both bread and pasta, their wild ancestors and synthetic hybrids) on the microbiota of their roots and surrounding soil is characterized. We isolated lines of bread wheat by hybridizing diploid (Aegilops tauschii) with tetraploid Triticum durum and crossed it with a modern cultivar of Triticum aestivum. The newly created, synthetic hybrid wheat, which recapitulate the breeding history of wheat through artificial selection, is found to support a microbiome enriched in beneficial Glomeromycetes fungi, but also in, potentially detrimental, Nematoda. We hypothesize that during wheat domestication this plant-microbe interaction diminished, suggesting an evolutionary tradeoff; sacrificing advantageous nutrient acquisition through fungal interactions to minimize interaction with pathogenic fungi. Increased plant selection for Glomeromycetes and Nematoda is correlated with the D genome derived from A. tauschii. Despite differences in their soil microbiota communities, overall wheat plants consistently show a low ratio of eukaryotes to prokaryotes. We propose that this is a mechanism for protection against soil-borne fungal disease and appears to be deeply rooted in the wheat genome. We suggest that the influence of plants on the composition of their associated microbiota is an integral factor, hitherto overlooked, but intrinsic to selection during wheat domestication.
Highlights
Selection of domesticated wheat varieties for improved yield has reduced their genetic diversity (Doebley et al, 2006; Purugganan and Fuller, 2009) which may be a factor which will hinder their future sustainability when faced with emerging pathogens and climate change
We observed from quantitative PCR (qPCR) targeting eukaryotic 18S and prokaryotic 16S rRNA that none of the rhizospheres of the wheat species examined in this study (Table 1) differs from each other in proportion of eukaryotes to prokaryotes (Supplementary Figure S1)
Values obtained in this work using 16S and 18S rRNA-specific qPCR are similar to those we previously reported from RNA-Seq-based data (Turner et al, 2013)
Summary
Selection of domesticated wheat varieties for improved yield has reduced their genetic diversity (Doebley et al, 2006; Purugganan and Fuller, 2009) which may be a factor which will hinder their future sustainability when faced with (re-) emerging pathogens and climate change. To understand how the genomic composition of wheat influences the recruitment of microorganisms associated with roots, the microbiota structure of four different wheat species, differing both in genomic content and in domestication and selection history have been analyzed (Figure 1). These include numerous lines of each of the following; the diploid wild A. tauschii (DD genome), tetraploid progenitor species T. turgidum spp. dicoccoides (AABB), domesticated pasta wheat T. turgidum spp. durum (AABB), and the hexaploid bread wheat T. aestivum (AABBDD) (Table 1). These F1 plants are hybrids in which one intact set of chromosomes (ABD) comes from the modern elite cultivar Paragon (domesticated and later artificially selected through agricultural usage), while the other set of chromosomes comes from a newly created SHW line (Figure 1 and Table 1)
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