Exploring Genetic Variation in Root Traits and Root–Fungal Associations in Aegilops tauschii

Wheat domestication and selection for aboveground traits may have influenced belowground traits, reducing genetic diversity critical for adaptation to stress such as drought. However, the impacts on root system architecture and root–endophytic fungal interactions remain unclear. This study evaluated variation in root traits and associations with arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) among nine diploid Aegilops tauschii accessions (wild progenitor), one tetraploid Triticum turgidum cv. ‘Langdon’ (LNG), and one hexaploid Triticum aestivum cv. ‘Norin 61’ (N61). Root traits and fungal colonization varied significantly among genotypes. All Ae. tauschii accessions showed superior root development and lower DSE colonization compared to LNG and N61. AMF colonization was highest in accessions AT76 and KU-2126 (54% and 53%, respectively), while N61 exhibited the highest specific root length (SRL) and DSE colonization. AMF positively correlated with most root traits (except SRL), while DSE showed the opposite trend. Although Ae. tauschii accessions shared broadly favorable root traits, variation in their fungal interactions were more pronounced. A clustering heatmap incorporating both root and biotic traits clustered the genotypes into four groups, clearly separating the Ae. tauschii accessions into two clusters based on their root characteristics and root-fungal associations. These results highlight the hidden interspecific and intraspecific variations in Ae. tauschii and its potential as a genetic resource for optimizing root–endophytic fungal interactions, and improving wheat resilience to biotic and abiotic stress in a changing climate.