Deciphering the genetic basis of wheat seminal root anatomy uncovers ancestral axial conductance alleles

Abstract

Root axial conductance, which describes the ability of water to move through the xylem, contributes to the rate of water uptake from the soil throughout the whole plant lifecycle. Under the rainfed wheat agro-system, grain-filling is typically occurring during declining water availability (i.e., terminal drought). Therefore, preserving soil water moisture during grain filling could serve as a key adaptive trait. We hypothesized that lower wheat root axial conductance can promote higher yields under terminal drought. A segregating population derived from a cross between durum wheat and its direct progenitor wild emmer wheat was used to underpin the genetic basis of seminal root architectural and functional traits. We detected 75 QTL associated with seminal roots morphological, anatomical and physiological traits, with several hotspots harbouring co-localized QTL. We further validated the axial conductance and central metaxylem QTL using wild introgression lines. Field-based characterization of genotypes with contrasting axial conductance suggested the contribution of low axial conductance as a mechanism for water conservation during grain filling and consequent increase in grain size and yield. Our findings underscore the potential of harnessing wild alleles to reshape the wheat root system architecture and associated hydraulic properties for greater adaptability under changing climate.

Phenotypic Diversity of Seminal Root Traits in Bread Wheat Germplasm from Different Origins

“…The angle at which roots emerge from the seed and penetrate the soil determines root system architecture [ 27 ]. In several laboratory studies regarding RGA, results were consistent with field findings [ 32 , 33 ]. Work performed on seedlings showed RGA patterns were correlated with adult root morphology [ 34 ].…”

Modifying root/shoot ratios improves root water influxes in wheat under drought stress

“…Thus suggesting a connection between root anatomy and transpiration regulation. In contrast, a comparison of the wild introgressions with previous genomic dissection of wild emmer QTLs conferring root axial conductance and xylem anatomy (Hendel et al, 2021) did not show any overlap. Thus, it suggests that the genetic regulation of adapting the gas exchange to favourable climatic periods is associated with root morphology, rather than anatomical modifications.…”

Root biology never sleeps

“…Root‐related strategies to mitigate drought stress related to root hydraulic architecture and water transport were also discussed (Maurel & Nacry, 2020). Root‐system‐level traits linked with water and nutrient use efficiency such as wheat root axial conductance (Hendel et al ., 2021), architectural traits in rice (Ruangsiri et al ., 2021) and maize (Kistler et al ., 2018) have been identified with a combination of shovelomics, phenotyping, functional genomics and modelling.…”