Quantifying rooting at depth in a wheat doubled haploid population with introgression from wild emmer

Abstract

Background and AimsThe genetic basis of increased rooting below the plough layer, post-anthesis in the field, of an elite wheat line (Triticum aestivum ‘Shamrock’) with recent introgression from wild emmer (T. dicoccoides), is investigated. Shamrock has a non-glaucous canopy phenotype mapped to the short arm of chromosome 2B (2BS), derived from the wild emmer. A secondary aim was to determine whether genetic effects found in the field could have been predicted by other assessment methods.MethodsRoots of doubled haploid (DH) lines from a winter wheat (‘Shamrock’ × ‘Shango’) population were assessed using a seedling screen in moist paper rolls, in rhizotrons to the end of tillering, and in the field post-anthesis. A linkage map was produced using single nucleotide polymorphism markers to identify quantitative trait loci (QTLs) for rooting traits.Key ResultsShamrock had greater root length density (RLD) at depth than Shango, in the field and within the rhizotrons. The DH population exhibited diversity for rooting traits within the three environments studied. QTLs were identified on chromosomes 5D, 6B and 7B, explaining variation in RLD post-anthesis in the field. Effects associated with the non-glaucous trait on RLD interacted significantly with depth in the field, and some of this interaction mapped to 2BS. The effect of genotype was strongly influenced by the method of root assessment, e.g. glaucousness expressed in the field was negatively associated with root length in the rhizotrons, but positively associated with length in the seedling screen.ConclusionsTo our knowledge, this is the first study to identify QTLs for rooting at depth in field-grown wheat at mature growth stages. Within the population studied here, our results are consistent with the hypothesis that some of the variation in rooting is associated with recent introgression from wild emmer. The expression of genetic effects differed between the methods of root assessment.

Root System Architecture and Its Association with Yield under Different Water Regimes in Durum Wheat

“…However, incorporating selection for root traits directly in a breeding program has been met with many challenges, foremost the difficulty of phenotyping large numbers of genotypes in a cost-and time-efficient manner (Mace et al, 2012). Several wheat studies have evaluated roots using different phenotyping methods including rhizotrons (Nagel et al, 2012;Lobet and Draye, 2013;Clarke et al, 2017), soil coring (Trachsel et al, 2011;Wasson et al, 2012;Wasson et al, 2014), lysimeters (Ehdaie et al, 2014;Elazab et al, 2016), hydroponics (Liu et al, 2015), paper roll culture and Petri dishes for seedling (Tomar et al, 2016), rhizoboxes (Fang et al, 2017, and X-ray-computed tomography (Gregory et al, 2003;Mairhofer et al, 2013;Colombi and Walter, 2017;Flavel et al, 2017). However, most of these techniques are either expensive or not precise enough and reproducible.…”

The interaction between wheat roots and soil pores in structured field soil

“…Our results are consistent with rhizotron studies of Friedli et al (2019) who found that deep rooting was not necessarily related to plant height. It is notable that we found that Shamrock, identified by Clarke et al (2017) as a deep rooting wheat, did not apear to have an increased rooting depth. White et al (2015) have suggested that yield stagnation in wheat may be partly explained by a poor rooting of modern wheats compared with older varieties.…”

“…Cadenza and Paragon have both been used as reference wheats for comparison of traits. Shamrock was selected for study because rhizotron studies have identified this wheat to be deep rooting ( Clarke et al , 2017 ). Xi19 is a Cadenza×Rialto cross and semi-dwarf, with the potential for high yields.…”

Genetic Relationship and Structural Variation of Root Growth Angle for Deep Rooting in Rice (Oryza sativa L.)

“…However, incorporating selection for root traits directly in a breeding program has been met with many challenges. Several studies have been reported for different root phenotyping methods including rhizotrons [19,20], soil coring [21], lysimeters [22], hydroponics [23] and rhizoboxes [24]. However, most of these techniques are either expensive or not precise enough and reproducible.…”