Sharp roots – Gaining improved root penetration ability of hard and dry soils from wild ancestors of wheat into modern wheat cultivars

Project Summary:

Drought is one of the largest yield limiting factors in global crop production including wheat. Changing climate is predicted to increase the intensity and frequency of drought events which further jeopardizes wheat production and food supply chains around the globe. Therefore, the identification of drought tolerant germplasm is crucial for the success of wheat in both current as well as future climatic scenarios. Identification of novel ideotypes/ phenotypes can aid in selection of wheat varieties for water limiting environments. Water is a mobile soil resource thus it tends to accumulate in the deeper soil strata as the topsoil dries out. To capture the leached water, deeper rooting is well proven strategy that has been shown to cope with drought stress in a variety of crop species including wheat. However, as the topsoil dries the mechanical impedance to root growth increases and hinders the deeper soil exploration for water and nutrients. Therefore, improving the root penetration ability of dry and hard soils (increased mechanical resistance to root growth) is crucial for the success of wheat under low water availability.

This project aims to improve the wheat root penetration ability of dry and hard soils to access the deeper soil water reserves. Root penetration ability is a complex trait and is known to be regulated by many root anatomical phenotypes including root lignin content, root diameter, cortical cell size, and root tip shapes. Since root tip is at the forefront of root growth, root tip shape has been shown to influence root penetration ability to a greater extent. Sharper root tips have been shown to bear lower mechanical resistance as the root pushes through hard soils analogous to pushing sharp vs blunt needles into a hard media. Therefore, selecting sharper root tips would aid in increasing root penetration ability.

In our preliminary analysis, we have found that wheat progenitors Triticum dicoccoides (wild emmer) and Aegilops tauschii (goat grass) have sharper root tips compared to modern Triticum aestivum (bread wheat). Likely due to sharper root tips, Ae. tauschii has 178 % and T. dicoccoides has a 94 % greater penetration ability than modern Triticum aestivum lines. Improved root penetration ability of wheat progenitors could be mobilized to modern wheat germplasm via wheat introgression lines (a cross between Triticum dicoccoides and Aegilops tauschii). Thus, the long-term goal is to utilize introgression lines to breed modern wheat cultivars with improved penetration ability of hard and dry soils and provide a better understanding of the involvement of root tip, anatomical phenotypes, and underlying genes regulating root penetration ability of hard soils. The specific objectives of the project are to identify Triticum dicoccoides and Aegilops tauschii introgression lines with sharper root tips and assess the root penetration ability of selected introgression lines to lay the foundation for the characterization of this important drought adaptation trait.

Increased penetration ability and deeper rooting are not only important for drought stress but also have the potential for carbon sequestration and increasing nitrogen use efficiency, thus our project also has huge industrial value. This project fits well into WGRC I/UCRC – FY23 priority area on “heat and drought stress”.