Wheat root systems as a breeding target for climate resilience

Abstract

In the coming decades, larger genetic gains in yield will be necessary to meet projected demand, and this must be achieved despite the destabilizing impacts of climate change on crop production. The root systems of crops capture the water and nutrients needed to support crop growth, and improved root systems tailored to the challenges of specific agricultural environments could improve climate resiliency. Each component of root initiation, growth and development is controlled genetically and responds to the environment, which translates to a complex quantitative system to navigate for the breeder, but also a world of opportunity given the right tools. In this review, we argue that it is important to know more about the ‘hidden half’ of crop plants and hypothesize that crop improvement could be further enhanced using approaches that directly target selection for root system architecture. To explore these issues, we focus predominantly on bread wheat (Triticum aestivum L.), a staple crop that plays a major role in underpinning global food security. We review the tools available for root phenotyping under controlled and field conditions and the use of these platforms alongside modern genetics and genomics resources to dissect the genetic architecture controlling the wheat root system. To contextualize these advances for applied wheat breeding, we explore questions surrounding which root system architectures should be selected for, which agricultural environments and genetic trait configurations of breeding populations are these best suited to, and how might direct selection for these root ideotypes be implemented in practice.

Root system architecture in cereals: progress, challenges and perspective

“…As described in Ober et al. (2021), the development of elite introgression lines for target root traits with similar above‐ground behavior would provide valuable materials for evaluating the value of the new trait in different environments or production. Likewise, the genetic framework described above and the availability of new genomics tools and advancements in the phenotyping methods would result in the plethora of genetic information related to RSA.…”

“…For example, the introduction of rye chromosome into bread wheat resulted in the development of cultivars with 1B.1R translocation, and introduction of alien segment from Agropyron elongatum as 7DL.7EL translocation, which have good drought adaptability due to the deeper roots (Kaggwa et al, 2015;Placido et al, 2013). As described in Ober et al (2021), the development of elite introgression lines for target root traits with similar above-ground behavior would provide valuable materials for evaluating the value of the new trait in different environments or production. Likewise, the genetic framework described above and the availability of new genomics tools and advancements in the phenotyping methods would result in the plethora of genetic information related to RSA.…”

The relationship between characteristics of root morphology and grain filling in wheat under drought stress

“…Wheat root system is the main place for water and nutrient absorption. Its morphological and physiological characteristics have a close relationship with the growth and development of wheat aboveground part, especially caryopses, thus affecting the formation of wheat yield and quality ( Ober et al, 2021 ). The absorption of water by wheat roots is not only restricted by physical and mechanical properties of soil, but also affected by root growth and metabolism.…”

Progenitor species hold untapped diversity for potential climate-responsive traits for use in wheat breeding and crop improvement

“…RSA plays a pivotal role in drought tolerance and nutrient acquisition and enhancing root systems is a target for improving climate resilience (recently reviewed by Ober et al 2021 ). Deeper roots can extract more water from subsoils, particularly during late developmental stages and grain fill, thereby improving yield in water limiting environments (Manschadi et al 2010 ).…”

“…tauschii (four QTLs) or tetraploid (durum; two QTLs) components of the synthetic. Ober et al ( 2021 ) reviewed the range of wheat trait variation reported in wheat as well as summarised available evidence linking deeper roots to access to soil moisture.…”