Dissecting the Genetic Basis of Grain Size and Weight in Barley (Hordeum vulgare L.) by QTL and Comparative Genetic Analyses

Abstract

Grain size and weight are crucial components of barley yield and quality and are the target characteristics of domestication and modern breeding. Despite this, little is known about the genetic and molecular mechanisms of grain size and weight in barley. Here, we evaluated nine traits determining grain size and weight, including thousand grain weight (Tgw), grain length (Gl), grain width (Gw), grain length-width ratio (Lwr), grain area (Ga), grain perimeter (Gp), grain diameter (Gd), grain roundness (Gr), and factor form density (Ffd), in a double haploid (DH) population for three consecutive years. Using five mapping methods, we successfully identified 60 reliable QTLs and 27 hotspot regions that distributed on all chromosomes except 6H which controls the nine traits of grain size and weight. Moreover, we also identified 164 barley orthologs of 112 grain size/weight genes from rice, maize, wheat and 38 barley genes that affect grain yield. A total of 45 barley genes or orthologs were identified as potential candidate genes for barley grain size and weight, including 12, 20, 9, and 4 genes or orthologs for barley, rice, maize, and wheat, respectively. Importantly, 20 of them were located in the 14 QTL hotspot regions on chromosome 1H, 2H, 3H, 5H, and 7H, which controls barley grain size and weight. These results indicated that grain size/weight genes of other cereal species might have the same or similar functions in barley. Our findings provide new insights into the understanding of the genetic basis of grain size and weight in barley, and new information to facilitate high-yield breeding in barley. The function of these potential candidate genes identified in this study are worth exploring and studying in detail.

Fine mapping qGL2H, a major locus controlling grain length in barley (Hordeum vulgare L.)

“…Identification and mapping QTL for grain size-related characteristics have been achieved in various genetic backgrounds (Walker et al 2013;Watt et al 2019;Xu et al 2018a;Zhou et al 2016). In many instances, the identified QTL share close homology to grain size-related genes identified in wheat and rice resulting in promising putative candidates for further research, although research of homologous gene regions in barley is restricted to a small number of publications (Bélanger et al 2014;Wang et al 2019;Watt et al 2019;Xu et al 2018a). Despite our current understanding of QTL regions contributing to grain size, only one study has fine mapped a major QTL and identified a potential candidate gene (Watt et al 2019).…”

Thep-coumaroyl arabinoxylan transferaseHvAT10underlies natural variation in whole-grain cell wall phenolic acids in cultivated barley

“…The eight 9K iSelect markers defining this QTL can be positioned on the current physical map at 482-500MB on 7H, corresponding to the location of HvAT10. Wang et al 28 also identified a QTL for grain length:width, grain perimeter, and grain roundness at the same location.…”

Harnessing Transcription Factors as Potential Tools to Enhance Grain Size Under Stressful Abiotic Conditions in Cereal Crops

“…In rice, maize, wheat, and barley thousands of quantitative trait loci (QTL) influencing grain size have collectively been detected, yet only a small fraction of underlying candidate genes have been functionally annotated using advanced molecular approaches such as gene cloning with the majority of studies in rice ( Ayoub et al., 2002 ; Huang et al., 2013 ; Walker et al., 2013 ; Chen et al., 2016 ; Yu et al., 2017 ; Azizi et al., 2019 ; Li et al., 2019 ; Wang Q. et al., 2019 ; Watt et al., 2019 ). Broadly, the regulatory pathways involved in grain size regulation are represented by: hormone signaling, IKU pathway, G-protein signaling, ubiquitin–proteasome pathway, the mitogen-activated protein kinase pathway and transcription factors ( Li and Li, 2016 ; Azizi et al., 2019 ).…”