Root system architecture in cereals: progress, challenges and perspective

Abstract

Roots are essential multifunctional plant organs involved in water and nutrient uptake, metabolite storage, anchorage, mechanical support, and interaction with the soil environment. Understanding of this 'hidden half' provides potential for manipulation of root system architecture (RSA) traits to optimize resource use efficiency and grain yield in cereal crops. Unfortunately, root traits are highly neglected in breeding due to the challenges of phenotyping, but could have large rewards if the variability in RSA traits can be fully exploited. Until now, a plethora of genes have been characterized in detail for their potential role in improving RSA. The use of forward genetics approaches to find sequence variations in genes underpinning desirable RSA would be highly beneficial. Advances in computer vision applications have allowed image-based approaches for high-throughput phenotyping of RSA traits that can be used by any laboratory worldwide to make progress in understanding root function and dissection of the genetics. At the same time, the frontiers of root measurement include non-invasive methods like X-ray computer tomography and magnetic resonance imaging that facilitate new types of temporal studies. Root physiology and ecology are further supported by spatiotemporal root simulation modeling. The discovery of component traits providing improved resilience and yield advantage in target environments is a key necessity for mainstreaming root-based cereal breeding. The integrated use of pan-genome resources, now available in most cereals, coupled with new in-field phenotyping platforms has the potential for precise selection of superior genotypes with improved RSA.

A major quantitative trait locus for wheat total root length associated with precipitation distribution

“…Plants may adopt different rooting strategies to meet changes in precipitation ( Wang et al, 2020 ). Optimization of RSA allows crops to better capture water and nutrients and improve tolerance in extreme environments ( Li et al, 2021 ; Maqbool et al, 2022 ).Therefore, we hypothesized that wheat growing in humid areas may not need a larger RSA to increase yield due to abundant precipitation, whereas in arid or semi-arid areas, wheat needs a better RSA to capture water and nutrients and satisfy the purpose of increasing yield. Thus, the local climate should be preferably considered when optimizing RSA in wheat breeding.…”

“…As a main trait for RSA, TRL is beneficial to increase yield potential and should be included in wheat ideotype ( Maqbool et al, 2022 ). QTrl.sicau-2SY-4D showed pleiotropic effects on TRL, RA, RV, RF, RDW, and SDW ( Figure 3 and Table 3 ).…”

“…Root system architecture (RSA) represents the shape and spatial distribution of roots underground, including root length, diameter, number, angle, density and so on ( Li et al, 2021 ). RSA is involved in water and nutrients utilization, production and storage of organic matter, bracing and anchoring, resisting abiotic stress, and interaction with soil microenvironment ( Maqbool et al, 2022 ). Breeding wheat varieties with optimized RSA is expected to increase world grain yield.…”

Translating controlled release systems from biomedicine to agriculture

“…For many of the more common agricultural and horticultural crops, basic root architecture (e.g. (Guo et al, 2020;Maqbool et al, 2022;Viana et al, 2022)), chemicals exuded into the soil (exudates) surrounding plant roots (rhizosphere) (e.g. (Weston and Mathesius, 2013;Schmelz et al, 2014;Tsunoda and van Dam, 2017)) are known, and biologists can manipulate many of the underlying genetics for these traits (e.g., (Atkinson et al, 2014;Soyano et al, 2019;Guo et al, 2020;Huang et al, 2021).…”

Transcriptomic analysis reveals the contribution of QMrl-7B to wheat root growth and development

“…In general, manipulation of root architecture traits, including root number, root length, root surface area (RA) and root volume (RV), especially the spatial configuration of the root system in the soil, is an essential approach to increase crop yields, which may represent an important component of a new green revolution ( Lynch, 2007 ; Meister et al., 2014 ). Unfortunately, root traits have been chronically overlooked in the traditional breeding due to their lack of aboveground visibility ( Maqbool et al., 2022 ).…”