Barley Developmental Mutants: The High Road to Understand the Cereal Spike Morphology

Abstract

Abstract:A better understanding of the developmental plan of a cereal spike is of relevance when designing the plant for the future, in which innovative traits can be implemented through pre-breeding strategies. Barley developmental mutants can be a Mendelian solution for identifying genes controlling key steps in the establishment of the spike morphology. Among cereals, barley (Hordeum vulgare L.) is one of the best investigated crop plants and is a model species for the Triticeae tribe, thanks to several characteristics, including, among others, its adaptability to a wide range of environments, its diploid genome, and its self-pollinating mating system, as well as the availability of its genome sequence and a wide array of genomic resources. Among them, large collections of natural and induced mutants have been developed since the 1920s, with the aim of understanding developmental and physiological processes and exploiting mutation breeding in crop improvement. The collections are not only comprehensive in terms of single Mendelian spike mutants, but with regards to double and triple mutants derived from crosses between simple mutants, as well as near isogenic lines (NILs) that are useful for genetic studies. In recent years the integration of the most advanced omic technologies with historical mutation-genetics research has helped in the isolation and validation of some of the genes involved in spike development. New interrogatives have raised the question about how the behavior of a single developmental gene in different genetic backgrounds can help in understanding phenomena like expressivity, penetrance, phenotypic plasticity, and instability. In this paper, some genetic and epigenetic studies on this topic are reviewed.

Multi-Locus Genome-Wide Association Studies for 14 Main Agronomic Traits in Barley

“…For main spike length (MSL), HORVU2Hr1G113880 corresponding to Cly1 gene, was identified at 2H:730,027,508–730,030,208 bp, which was 3 Mb from the QTN qtnMSL-2H-7 (2H: 727,985,438 bp) for MSL (Table 2 ; Figure 2 ). Cly1 encodes for an AP2-protein that inhibits development of flower (Nair et al, 2010 ; Terzi et al, 2017 ). HvAP2 regulates the length of a critical developmental window required for the elongation of the inflorescence internodes in barley (Houston et al, 2013 ).…”

Genetic Interactions of Awnness Genes in Barley

“…The development of grass awns has become a topic of intense research largely owing to its important function in grain filling [ 1 ]. Awn in barley ( Hordeum vulgare L.) is more diverse than in rice and wheat [ 20 ]. The awnness trait can be distinguished into different phenotypes, including awnless, straight (long, longer than the length of spike axis; short, shorter than the length of spike axis; and awnlet, shorter than 1 cm), hooded, leafy, and crooked at the end of a lemma ( Figure 1 ).…”

Genetic Loci Underlying Awn Morphology in Barley

“…Microscopic analysis of barley awn transverse and longitudinal sections reveals that the green cells of awns are arranged into two long strands of chlorenchyma, which are placed in between the three vascular bundles (Figure 1) [11,12]. Barley awns are highly diverse in morphology, ranging from straight to hooded or crooked shapes [14]. The development of awns is controlled by a set of genetic loci [15], of which a few have recently been cloned.…”