Detection and verification of malting quality QTLs using wild barley introgression lines

Abstract

A malting quality quantitative trait locus (QTL) study was conducted using a set of 39 wild barley introgression lines (hereafter abbreviated with S42ILs). Each S42IL harbors a single marker-defined chromosomal segment from the wild barley accession 'ISR 42-8' (Hordeum vulgare ssp. spontaneum) within the genetic background of the elite spring barley cultivar 'Scarlett' (Hordeum vulgare ssp. vulgare). The aim of the study was (1) to verify genetic effects previously identified in the advanced backcross population S42, (2) to detect new QTLs, and (3) to identify S42ILs exhibiting multiple QTL effects. For this, grain samples from field tests in three different environments were subjected to micro malting. Subsequently, a line x phenotype association study was performed with the S42ILs in order to localize putative QTL effects. A QTL was accepted if the trait value of a particular S42IL was significantly (P < 0.05) different from the recurrent parent as a control, either across all tested environments or in a particular environment. For eight malting quality traits, altogether 40 QTLs were localized, among which 35 QTLs (87.5%) were stable across all environments. Six QTLs (15.0%) revealed a trait improving wild barley effect. Out of 36 QTLs detected in a previous advanced backcross QTL study with the parent BC(2)DH population S42, 18 QTLs (50.0%) could be verified with the S42IL set. For the quality parameters alpha-amylase activity and Hartong 45 degrees C, all QTLs assessed in population S42 were verified by S42ILs. In addition, eight new QTL effects and 17 QTLs affecting two newly investigated traits were localized. Two QTL clusters harboring simultaneous effects on eight and six traits, respectively, were mapped to chromosomes 1H and 4H. In future, fine-mapping of these QTL regions will be conducted in order to shed further light on the genetic basis of the most interesting QTLs.

Fig. 1

SSR map with 68 significant (P < 0.05) line × trait associations for 39 S42ILs and eight malting quality traits. The chromosomes are shown as black bars with cM values for SSR loci following the order of von Korff et al. (2004). The extent of Hsp introgressions are given in grey bars right to the chromosomes. The associations are illustrated as symbols below the S42ILs. They either reveal a favorable (filled symbols) or unfavorable (empty symbols) Hsp effect. Associations solely detected as line x environment interaction effect are marked by an asterisk right to the symbol