Genetic Loci Underlying Awn Morphology in Barley.

Barley awns are highly active in photosynthesis and account for 30-50% of grain weight in barley. They are diverse in length, ranging from long to awnless, and in shape from straight to hooded or crooked. Their diversity and importance have intrigued geneticists for several decades. A large collection of awnness mutants are available-over a dozen of them have been mapped on chromosomes and a few recently cloned. Different awnness genes interact with each other to produce diverse awn phenotypes. With the availability of the sequenced barley genome and application of new mapping and gene cloning strategies, it will now be possible to identify and clone more awnness genes. A better understanding of the genetic basis of awn diversity will greatly facilitate development of new barley cultivars with improved yield, adaptability and sustainability.

Genetic Interactions of Awnness Genes in Barley.

Awns are extending structures from lemmas in grasses and are very active in photosynthesis, contributing directly to the filling of the developing grain. Barley (Hordeum vulgare L.) awns are highly diverse in shape and length and are known to be controlled by multiple awn-related genes. The genetic effects of these genes on awn diversity and development in barley are multiplexed and include complementary effect, cumulative effect, duplicate effect, recessive epistasis, dominant epistasis, and inhibiting effect, each giving a unique modified Mendelian ratio of segregation. The complexity of gene interactions contributes to the awn diversity in barley. Excessive gene interactions create a challenging task for genetic mapping and specific strategies have to be developed for mapping genes with specific interactive effects. Awn gene interactions can occur at different levels of gene expression, from the transcription factor-mediated gene transcription to the regulation of enzymes and metabolic pathways. A better understanding of gene interactions will greatly facilitate deciphering the genetic mechanisms underlying barley awn diversity and development.

Genetic analysis reveals four interacting loci underlying awn trait diversity in barley (Hordeum vulgare).

Barley (Hordeum vulgare) awns contribute to grain yield, but the genetic basis of awn development remains largely unclear. Five barley lines differing in awn traits and row types were used to create four F2 populations. Genetic analyses revealed that four pairs of genes were involved in awn development: A/a (awnless/awned), B/b (awnless/awned), H/h (hooded/straight), and L/l (long/short). Of these four loci, A, H and L functioned on both central rows (CR) and lateral rows (LR) of the barley spikes, while B exhibited effect only on LR. A and B had duplicate effects on LR, and both showed dominant epistasis to loci H and L, whereas H was epistatic to L. Meanwhile, A and B were found to be genetically linked, with a row-type locus V located between them. The genetic distances of A-V and B-V were estimated to be 9.6 and 7.7 cM, respectively. Literature search suggested that A, H and V may correspond to the reported Lks1, Kap1 and Vrs1, respectively, whereas B is a novel gene specifically controlling awn development on LR, designated as Lsa1 for lateral spikelet awnless 1. The only barley homolog of wheat awn inhibitor gene B1, HORVU2Hr1G077570, is a potential candidate of Lsa1.

[Genetic analysis on poly-row-and-branched spike mutant in barley].

In order to study the inheritance of poly-row-and-branched spike (PRBS) in barley, the row types of F1s, F2s, F3s of four crosses ( six-row x two-row, PRBS x two-row, PRBS x six-row and six-row x PRBS ) were investigated and analyzed. The results showed that one pair of recessive genes controls the PBRS mutant trait, which has recessive epistasis on the genes controlling two-row vs. six-row.