Abstract
Wide crosses between genetically diverged parents may reveal novel loci for crop improvement that are not apparent in crosses between elite cultivars. The landrace Chevallier was a noted malting barley first grown in 1820. To identify potentially novel alleles for agronomic traits, Chevallier was crossed with the modern malting cultivar NFC Tipple generating two genetically diverse recombinant inbred line populations. Genetic maps were produced using genotyping-by-sequencing and 384-SNP genotyping, and the populations were phenotyped for agronomic traits to allow the identification of quantitative trait loci (QTL). Within the semi-dwarf 1 (sdw1) region on chromosome 3H Chevallier conferred increased plant height and reduced tiller number, with QTL for these traits explaining 79.4% and 35.2% of the phenotypic variance observed, respectively. Chevallier was also associated with powdery mildew susceptibility, with a QTL on 1H accounting for up to 19.1% of the variance and resistance at this locus most likely resulting from an Mla variant from Tipple. Two novel QTL for physiological leaf spotting were identified on 3H and 7H, explaining up to 17.1% of the variance and with the Chevallier allele reducing symptom severity on 7H. Preliminary micromalting analysis was also undertaken to compare the malting characteristics of Chevallier and Tipple. Chevallier malt contained significantly lower levels of both α-amylase and wort β-glucan than Tipple malt, however no significant differences were observed for the remaining malting parameters measured. This suggests that the most obvious improvements in barley since the introduction of Chevallier are for agronomic traits such as height, yield and lodging resistance rather than for malting characteristics. Overall, our results demonstrate that this wide cross between Chevallier and Tipple may provide a source of novel QTL for barley breeding.
Highlights
Two-row barleys, which are considered to produce premium malt for the beverage industry and have historically been preferred by European maltsters, are increasingly being favoured over six-row type in North America [1]
Two separate bi-parental crosses were developed by single seed descent using Chevallier (JIC Germplasm Resources Unit (GRU) accession 4851) and NFC Tipple (Syngenta Seeds, Ltd), which has the pedigree (NFC497-12 × Cork) × Vortex [12]
Chevallier was more susceptible to powdery mildew than Tipple in all environments, with the predicted mean values between the parents being significantly different in all years (Table 1)
Summary
Two-row barleys, which are considered to produce premium malt for the beverage industry and have historically been preferred by European maltsters, are increasingly being favoured over six-row type in North America [1]. For continued improvement of two-row barleys, novel genes for agronomic, disease resistance and grain quality traits are needed. Due to its professed superior malt quality, good yield on chalky or sandy soils and the regularity of the shape, colour and size of its grain [4], up to 80% of the barley grown in England in the 1880s was derived from Chevallier [5]. There is much interest in increasing genetic diversity within modern barley germplasm and studies of landrace barleys have identified novel alleles associated with abiotic and biotic stresses [7, 8] and malting quality [9, 10]. It is possible that Chevallier may possess favourable characteristics or novel alleles that could be of potential use in modern breeding programmes
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