Abstract:
Wheat (Triticum aestivum L.) production in the world is challenged by different biotic and
abiotic stresses, which are increasing with climate change. Unravelling the molecular
genetics quantitative trait loci (QTL), candidate genes and proteins of root traits is essential
wheat root trait improvement through breeding. One hundred and three recombinant inbred
lines (RILs) RILs of Synthetic W7984 × Opata M85 and 14 pairs of near-isogenic lines
(NILs: pairs of genetically identical lines except for genomic regions (GRs)) of wheat were
used to phenotype root traits in a semi-hydroponic system. The composite interval mapping
method was used to discover QTL for root traits from RILs. Candidate genes and proteins
for root traits were identified from NILs through genotype-phenotype association analysis,
and label-free proteomics, respectively. The RILs exhibited significant variation in root
traits; 14 QTL for eight root traits were identified mainly on chromosome groups 5, 6 and 7.
Important QTL for shallow root (Q.rd.uwa.7BL: Xbarc50) and high RM (Q.rm.uwa.6AS:
Xgwm334) were validated in two independent F2 populations of Synthetic W7984 × Chara
and Opata M85 × Cascade, respectively. Separately, 10 of 14 NIL pairs showed significant
variation between their isolines for root traits; 15 putative candidate genes for root traits,
including outstanding genes TraesCS4A02G185300 and TraesCS4A02G442700 encoding
UDP-glycosyltransferase and TraesCS4A02G330900 encoding leucine-rich repeat receptorlike
protein kinase were identified on targeting GRs on chromosomes 4BS, 4BL, 4AS, and
7AL of NILs. Furthermore, three candidate protein biomarkers for total root length and root
dry mass in NIL pairs targeting GRs on chromosomes 4A and 7A—asparagine synthetase
(TraesCS4A02G109900), signal recognition particle 19 kDa protein
(TraesCS7A02G333600) and 3,4-dihydroxy-2-butanone 4-phosphate synthase
(TraesCS7A02G415600)—with consistent gene expressions at protein and mRNA
transcription (qRT-PCR) levels were identified. Our research provides an improved
understanding of molecular control of root traits and potential for marker-assisted root
breeding in wheat.
