Identification and validation of QTL and their associated genes for pre-emergent metribuzin tolerance in hexaploid wheat (Triticum aestivum L.)

Abstract

BackgroundHerbicide tolerance is an important trait that allows effective weed management in wheat crops. Genetic knowledge of metribuzin tolerance in wheat is needed to develop new cultivars for the industry. Here, we evaluated metribuzin tolerance in a recombinant inbred line (RIL) mapping population derived from Synthetic W7984 and Opata 85 over two consecutive years to identify quantitative trait loci (QTL) contributing to the trait. Herbicide tolerance was measured by two chlorophyll traits, SPAD chlorophyll content index (CCI) and visual senescence score (SNS). The markers associated with major QTL from Synthetic W7984, positively contributing to reduced phytotoxic effects under herbicide treatment were validated in two F3/4 recombinant inbred populations developed from crosses of Synthetic W7984 × Westonia and Synthetic W7984 × Lang.ResultsComposite interval mapping (CIM) identified four QTL, two on chromosome 4A and one each on chromosomes 2D and 1A. The chromosomal position of the two QTL mapped on 4A within 10 cM intervals was refined and validated by multiple interval mapping (MIM). The major QTL affecting both measures of tolerance jointly explained 42 and 45% of the phenotypic variation by percentage CCI reduction and SNS, respectively. The identified QTL have a pure additive effect. The metribuzin tolerant allele of markers, Xgwm33 and Xbarc343, conferred lower phytotoxicity and explained the maximum phenotypic variation of 28.8 and 24.5%, respectively. The approximate physical localization of the QTL revealed the presence of five candidate genes (ribulose-bisphosphate carboxylase, oxidoreductase (rbcS), glycosyltransferase, serine/threonine-specific protein kinase and phosphotransferase) with a direct role in photosynthesis and/or metabolic detoxification pathways.ConclusionMetribuzin causes photo-inhibition by interrupting electron flow in PSII. Consequently, chlorophyll traits enabled the measure of high proportion of genetic variability in the mapping population. The validated molecular markers associated with metribuzin tolerance mediating QTL may be used in marker-assisted breeding to select metribuzin tolerant lines. Alternatively, validated favourable alleles could be introgressed into elite wheat cultivars to enhance metribuzin tolerance and improve grain yield in dryland farming for sustainable wheat production.Electronic supplementary materialThe online version of this article (10.1186/s12863-018-0690-z) contains supplementary material, which is available to authorized users.

QTL Mapping Using a High-Density Genetic Map to Identify Candidate Genes Associated With Metribuzin Tolerance in Hexaploid Wheat (Triticum aestivum L.)

“…In comparison to the study done by Bhoite et al (2018), who reported metribuzin tolerance QTL on chromosomes 1A, 2D, and 4A, we detected six new loci in this study. Blasting the QTL flanking markers with the wheat reference genome RefV1.0 revealed that the 2D QTL overlapped in the two studies, as a flanking marker "DArT1219191" of QMCC.UWA.2DS fell into the interval of Qsns.uwa.2DS.…”

“…Most of the identified QTL were related to metabolic detoxification, especially the P450 pathway and xenobiotic transmembrane transporter activity. RCC offers a rapid and non-destructive method for evaluating senescence in wheat seedlings in the metribuzin treatment as chlorophyll content and senescence are highly correlated (Bhoite et al, 2018). Metribuzin mainly inhibits photosynthesis by competing with plastoquinone at the plastoquinone-binding site on the D1 protein in the PSII complex (Pan et al, 2012).…”

“…The trays were sprayed with water to 100% field capacity one day before the herbicide application. The preemergent treatment of metribuzin (400 g ai ha −1 ) was as described in Bhoite et al (2018). Specifically, metribuzin was sprayed in two passes, with the cabinet sprayer calibrated to deliver a spray volume of 106.19 L ha −1 , 50 cm above the target, with a forward speed of 3.6 km h −1 and a pressure of 200 kPa in two flat-fan nozzles (TeeJet XR11001 flat-fan, Spraying Systems Co, Wheaton, IL, USA) ( Figure S1, doi: 10.6084/m9.figshare.12570113).…”

“…Genetic studies on metribuzin tolerance are limited. Bhoite et al (2018) conducted a quantitative trait loci (QTL) mapping study using the International Triticeae Mapping Initiative (ITMI) population (Synthetic W7984 × Opata 85). Pilcher et al (2017) identified 169 (upregulated) and 127 (downregulated) genes in a metribuzin-tolerant and a susceptible wheat genotype that had significant differential expression in response to metribuzin.…”

Genetic dissection of photosynthetic performances in maize under drought-stressed and well-watered environments

“…Epistasis, i.e. the interactions between genetic loci, is also thought to contribute to photosynthetic performances variations [49][50][51]. In maize, Li et al [46] reported that SPAD was controlled by 2 major genes with AD-epistatic effects and polygene with AD effects by mixed major gene plus polygene genetic model.…”