Resequencing the Vrs1 gene in Spanish barley landraces revealed reversion of six-rowed to two-rowed spike

Six-rowed spike 1 (Vrs1) is a gene of major importance for barley breeding and germplasm management as it is the main gene determining spike row-type (2-rowed vs. 6-rowed). This is a widely used DUS trait, and has been often associated to phenotypic traits beyond spike type. Comprehensive re-sequencing Vrs1 revealed three two-rowed alleles (Vrs1.b2; Vrs1.b3; Vrs1.t1) and four six-rowed (vrs1.a1; vrs1.a2; vrs1.a3; vrs1.a4) in the natural population. However, the current knowledge about Vrs1 alleles and its distribution among Spanish barley subpopulations is still underexploited. We analyzed the gene in a panel of 215 genotypes, made of Spanish landraces and European cultivars. Among 143 six-rowed accessions, 57 had the vrs1.a1 allele, 83 were vrs1.a2, and three showed the vrs1.a3 allele. Vrs1.b3 was found in most two-rowed accessions, and a new allele was observed in 7 out of 50 two-rowed Spanish landraces. This allele, named Vrs1.b5, contains a ‘T’ insertion in exon 2, originally proposed as the causal mutation giving rise to the six-row vrs1.a2 allele, but has an additional upstream deletion that results in the change of 15 amino acids and a potentially functional protein. We conclude that eight Vrs1 alleles (Vrs1.b2, Vrs1.b3, Vrs1.b5, Vrs1.t1, vrs1.a1, vrs1.a2, vrs1.a3, vrs1.a4) discriminate two and six-rowed barleys. The markers described will be useful for DUS identification, plant breeders, and other crop scientists.This work was supported by the Spanish Ministry of Economy, Industry and Competitiveness grants AGL2010-21929, AGL2013-48756-R, RFP2012-00015-00-00, RTA2012-00033-C03-02, and EUI2009-04075 (national code for Plant-KBBE project ExpResBar). CPC was funded by the Spanish Ministry of Economy, Industry and Competitiveness grant no. BES-2011-045905 (linked to project AGL2010-21929). TK and SS were supported by a research fund by the Ministry of Agriculture, Forestry, and Fisheries of Japan (Genomics for Agricultural Innovation grants no. TRS1002). SS was supported by a Grant-in-Aid from the Japan Society for the Promotion of Science (JSPS) Postdoctoral Fellow for Research Abroad and a Grant-in-Aid for Young Scientists (B) (no. 16 K18635)

Candidate genes underlying QTL for flowering time and their interactions in a wide spring barley (Hordeum vulgare L.) cross

Response to vernalization and photoperiod are the main determinants controlling the time to flowering in temperate cereals. While the individual genes that determine a plant's response to these environmental signals are well characterized, the combinatorial effect on flowering time of allelic variants for multiple genes remains unresolved. This study investigated the genetic control of flowering-time in a biparental population of spring barley, derived from a wide cross between a late-flowering European and an early-flowering North-American cultivar. While the major flowering time genes are not segregating in the Beka × Logan cross, large variation in flowering was observed. We identified five QTL, with both parents found to contribute early alleles. The catalog of QTL discovered aligns with several candidate genes affecting flowering time in barley. The combination of particular alleles at HvCEN, HvELF3 and HvFT1 in Logan are responsible for the earliness of this cultivar. Interestingly, earliness for flowering could be further enhanced, with Beka found to contribute three early alleles, including a QTL co-locating with a HvFD-like gene, suggesting that there are diverse aspects of the flowering-time pathway that have been manipulated in these two cultivars. Epistatic interactions between flowering-time QTL or candidate genes were observed in field data and confirmed under controlled conditions. The results of this study link photoperiod-dependent flowering-time genes with earliness per se genes into a single model, thus providing a unique framework that can be used by geneticists and breeders to optimize flowering time in barley.This work was supported by the Spanish Ministry of Economy and Competitiveness (grant numbers AGL2010-21929 and AGL2013-48756-R), the Spanish Ministry of Economy and Competitiveness, the Agencia Estatal de Investigación, and the European Regional Development Fund (grant number AGL2016–80967-R), and Government of Aragon (Research Group A08_20R)

Heading date QTL in a spring × winter barley cross evaluated in Mediterranean environments

Heading date is a key trait for the adaptation of barley to Mediterranean environments. We studied the genetic control of flowering time under Northern Spanish (Mediterranean) conditions using a new population derived from the spring/winter cross Beka/Mogador. A set of 120 doubled haploid lines was evaluated in the field, and under controlled temperature and photoperiod conditions. Genotyping was carried out with 215 markers (RFLP, STS, RAPD, AFLP, SSR), including markers for vernalization candidate genes, HvBM5 (Vrn-H1), HvZCCT (Vrn-H2), and HvT SNP22 (Ppd-H1). Four major QTL, and the interactions between them, accounted for most of the variation in both field (71–92%) and greenhouse trials (55–86%). These were coincident with the location of the major genes for response to vernalization and short photoperiod (Ppd-H2 on chromosome 1H). A major QTL, near the centromere of chromosome 2H was the most important under autumn sowing conditions. Although it is detected under all conditions, its action seems not independent from environmental cues. An epistatic interaction involving the two vernalization genes was detected when the plants were grown without vernalization and under long photoperiod. The simultaneous presence of the winter Mogador allele at the two loci produced a marked delay in heading date, beyond a mere additive effect. This interaction, combined with the effect of the gene responsive to short photoperiod, Ppd-H2, was found responsible of the phenomenon known as short-day vernalization, present in some of the lines of the population