Genome-Wide Association Mapping of Major Root Length QTLs Under PEG Induced Water Stress in Wheat.

Habtamu Ayalew,Chunji Liu,Andreas Börner,Hui Liu,Guijun Yan,Borislav Kobiljski

doi:10.3389/fpls.2018.01759

Abstract

Roots are vital plant organs that determine adaptation to various soil conditions. The present study evaluated a core winter wheat collection for rooting depth under PEG induced early stage water stress and non-stress growing conditions. Analysis of phenotypic data indicated highly significant (p < 0.01) variation among genotypes. Broad sense heritability of 59 and 73% with corresponding genetic gains of 7.6 and 9.7 (5% selection intensity) were found under non-stress and stress conditions, respectively. The test genotypes were grouped in to three distinct clusters using unweighted pair group method with arithmetic mean (UPGMA) clustering based on maximum Euclidian distance. The first three principal components gave optimum mixed linear model for genome wide association study (GWAS). Linkage disequilibrium (LD) analysis showed significant LD (p < 0.05) amongst 15% of total marker pairs (25,125). Nearly 16% of the significant LDs were among inter chromosomal marker pairs. GWAS revealed five significant root length QTLs spread across four chromosomes. None of the identified QTLs were common between the two growing conditions. Stress specific QTLs, combined explaining 31% of phenotypic variation were located on chromosomes 2B (wPt6278) and 3B (wPt1159). Similarly, two of the three QTLs (wPt0021 and wPt8890) identified under the non-stress condition were found on chromosomes 3B and 5B, respectively. The B genome showed significant importance in controlling root growth both under stress and non-stress conditions. The identified markers can potentially be validated and used for marker assisted selection.

Highlights

Common wheat (Triticum aestivum L.) is one of the earliest cereals ever domesticated and is currently one of the major sources of food and feed in the world
Crop productivity in dry areas can be improved through appropriate exploitation of available genetic variability of crop plants to better adapt to climate change (Pieruschka and Lawson, 2015; Reynolds and Langridge, 2016)
This study was conducted to (1) characterize genotypic and phenotypic diversity of a core winter wheat collection, (2) analyze Linkage disequilibrium (LD) and population structure, and (3) identify genomic regions significantly associated with root length under water stress and non-water stress growing conditions

Summary

Introduction

Common wheat (Triticum aestivum L.) is one of the earliest cereals ever domesticated and is currently one of the major sources of food and feed in the world. Wheat is adapted to diverse climatic zones including drought prone areas (Tardif et al, 2007; Monneveux et al, 2012). Reintroducing valuable alleles from wild progenitors of crop plants helps enrich domesticated gene pool (Feldman and Millet, 2001; Gur and Zamir, 2004). In this regard, wild emmer (Triticum turgidum) has been reported to harbor rich allelic diversity for numerous traits, including deep rooting for water stress resistance (Peng et al, 2012; Merchuk-Ovnat et al, 2017)

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Discussion

Conclusion