Differences in Root Morphologies of Contrasting Wheat (Triticum aestivum) Genotypes Are Robust of a Drought Treatment

Abstract

We aimed to assess the effect of water deprivation on root traits and to establish if the wheat cultivars Spica and Maringa would be useful as parental germplasm for a genetic analysis of root traits. Plants were grown in two markedly different soils under well-watered and water-limited treatments in controlled environment growth cabinets. The drought treatment was imposed as a gradual depletion of water over 28 days as seedlings grew from a defined starting moisture content. The root traits analyzed included length, nodal root number, thickness and nodal root angle. The relative differences in traits between genotypes generally proved to be robust in terms of water treatment and soil type. Maringa had a shallower nodal root angle than Spica, which was driven by the nodal roots. By contrast, the seminal roots of Maringa were found to be similar to or even steeper than those of Spica. We conclude that the differences in root traits between Spica and Maringa were robust to the drought treatment and soil types. Phenotyping on well-watered soil is relevant for identifying traits potentially involved in conferring water use efficiency. Furthermore, Spica and Maringa are suitable parental germplasm for developing populations to determine the genetics of key root traits.

Clear effects on root system architecture of winter wheat cultivars (Triticum aestivum L.) from cultivation environment and practices

“…Exemplifying this is the results in nodal root angle which this study shows to be linked to yield in a growth stage and precrop dependent manner. Changes in nodal root angle are usually associated with the depletion of soil resources such as water and nutrients [49][50][51] , therefore this highly dependent correlation highlights the diversity of the environment and the importance of understanding the environment to better adapt the RSA. These may go some way toward understanding why precrop effects are not always reported as positive 52 .…”

Physical Mapping of QTLs for Root Traits in a Population of Recombinant Inbred Lines of Hexaploid Wheat

“…The Maringa genotype we used is a Brazilian cultivar that had the Rht-B1b semi-dwarfing gene [ 28 ] introgressed, while Spica is an older Australian cultivar with the wild-type Rht genes (tall) that has been used extensively in the study of late maturity α-amylase [ 29 ]. These genotypes differ significantly in various root traits including nodal root number, nodal root angle, seminal root angle and root hair length [ 10 ]. The Spica and Maringa parental lines first underwent single-seed descent for at least six generations before being crossed to generate an F 2 population.…”

“…The soil was prepared by mixing sieved potting soil with river sand (final composition 30% v / v ) and 1 g L −1 Aboska fertiliser as described previously [ 10 ]. The soil was watered to pot capacity before sowing and then watered daily over the growth period.…”

“…If there was insufficient time to complete the scoring on harvest day, the plants in plastic bags were stored overnight at 4 °C in the dark and scored the next day. The root traits assayed followed methods described previously [ 10 ]. The traits assayed included the root angle (the angle between the pair of second whorl leaf nodal roots on either side of the main stem, the pair of first whorl leaf nodal roots was measured if the second whorl had not yet developed); the total number of nodal roots present on the main stem and tillers; the nodal roots per stem (total nodal root number divided by the total number of stems); the root dry weight; and the average root diameter based on a WinRHIZO Pro (Regent Instruments Inc., Quebec, QC, Canada) analysis of scanned primary roots, root-to-shoot ratio and the specific root length (root length of scanned primary root divided by the dry weight of the primary root).…”

“…Identifying molecular markers and genes associated with specific root traits will enable breeders to develop germplasm better suited to particular conditions. We undertook a genetic analysis of recombinant inbred lines (RILs) derived from a cross between Spica and Maringa—two hexaploid wheat genotypes with highly contrasting root traits [ 10 ]. The RILs were grown in soil and scored for seven root traits and two shoot traits.…”