D genome acquisition and modern breeding have had a strong impact on interaction of bread wheat Triticum aestivum with ACC deaminase producers in the rhizosphere

Wheat has undergone several domestication events combined to genomic hybridization, including the acquisition by Triticum dicoccon (AABB genome) of the D genome from Aegilops tauschii, which after subsequent domestication gave rise to current bread wheat Triticum aestivum (AABBDD genome). The D genome has had a marked influence on wheat traits and is likely to modulate the functioning of beneficial wheat-microbe interactions, but data are scarce. Here, we tested the hypothesis that the genome D could be important for wheat interactions with 1-aminocyclopropane-1-carboxylate (ACC) deaminase producers, a key microbial functional group that can enhance plant performance by fine-tuning ethylene metabolism in plant roots. A range of wheat lines from T. aestivum (AABBDD), T. diccocon (AABB) and Ae. tauschii (DD) were compared based on abundance (qPCR on acdS gene marker), diversity (Illumina MiSeq) and potential ACC deaminase activity (colorimetric assays) of ACC deaminase producers in the rhizosphere. Results show that the abundance of ACC deaminase producers was lower for D-genome wheats than D-negative T. dicoccon, but ACC deaminase potential activity was lower for D-genome Ae. tauschii and T. aestivum landraces than T. aestivum cultivars (recent and old) and D-negative T. dicoccon. Community structure of Ae. tauschii and T. dicoccon differed from that of T. aestivum, and differences occurred also between various genotype categories of T. aestivum. Overall, acquisition of the D genome has had a significant impact, distinct if not opposite to the impact of recent bread wheat breeding, on the ability of T. aestivum to interact with ACC deaminase producers.