Putting Life-Cyle Events of Barley on the Map

Breeding programmes are generally concerned with yield improvement and yield stability under a broad spectrum of environments. In fact, these programmes are reliant on the various investments in growth, reproduction and survival of plants and seeds. By monitoring phenological traits of one same plant, this study aims to understand how the sum total of properties of a plant determines its performance.

To allow robust and accurate associations between genotypes and phenotypes, 935 Recombinant Inbred Lines (RILs) were developed from crosses (F₁) between a cultivated barley, Morex, and four wild barleys, followed by a backcross (BC₁) with Morex, subsequent intercrossing of the BC₁F₁ populations, thereafter selfing and single seed descent selection was applied to obtain the RILs (BC₁F₆).  A set of 384 polymorphic and parent-specific single nucleotide polymorphism (SNP) markers from Barley Oligonucleotide Pool Assay 1 (BOPA1) were chosen to genotype these RILs. Eleven growth stages marking the vegetative and generative phases, such as leaf growth, tiller and node formation, and flowering time were monitored in four replicates of each RIL. The number of tillers, spike length, number of seeds per spike, plant height, seed dormancy, seed size and shape were measured for each replicate, too.

Association studies were conducted for each trait and the results were put on the map on a chronological order. Quantitative trait loci (QTLs) were detected on the vicinity of the positions previously reported by other studies. The well-known flowering genes such as Ppd-H1, Eam6 and FT1, and SD2, a QTL for seed dormancy, explained the vast differences in vegetative and generative growth, and yield-related traits. The statistical significance -or insignificance- of these loci varied, however, throughout plant development and growth. The results of our study suggested that there is a cluster of QTLs around the position of the major QTL for seed dormancy SD1, with specific contributions of the different wild barley genotypes. Currently the major QTL are being confirmed and fine-mapped using Heterogenous Inbred Families (HIFs) derived from lines with residual heterozygosity.