| Pre-harvest sprouting (PHS) and caryopsis dormancy have been ever-present concerns in malting barley (Hordeum vulgare L.). Barley with low dormancy combined with the wet, cool weather conditions in recent years has caused serious PHS problems in the upper Midwest United States. Fourteen barley genotypes were grown in experiments conducted in the greenhouse and in the field at Fargo and Osnabrock, ND, in 2004 and 2005. Germination percentage (GP) on hand-threshed caryopses, GP of intact spikes following artificial rain (AR) treatment, Stirring Number (SN), barley α-amylase activity, and malt a-amylase activity were measured. The measurement of GP at 72 h consistently identified genotypes with low dormancy and was recommended as a method to differentiate dormancy levels among genotypes due to its simplicity, no need for special equipments, quickness, and slightly higher repeatability compared with the AR treatment. Measurement of SN on field-weathered caryopses is perhaps a promising method for predicting PHS resistance due to its moderate repeatability; however, additional research needs to be conducted to improve the repeatability of this method. The moderately strong correlations between greenhouse and field results suggest that greenhouse evaluations can be used to determine dormancy levels in barley. The fourteen barley genotypes tested were divided into three groups. C93-3230-24 was dormant and highly PHS-resistant, 'Stander' and 'Legacy' were non-dormant and highly PHS-susceptible, and the remaining genotypes were moderately dormant and moderately PHS-susceptible. The moderate associations between malt α-amylase activity and caryopsis dormancy at harvest maturity suggested that cultivars with higher levels of malt α-amylase activity generally have lower dormancy at harvest and may be more prone to PHS. A quantitative trait locus (QTL) region close to the telomere on the long arm of chromosome 5H (5HL) was consistently identified in three doubled-haploid populations ('Harrington'/'Morex', 'Chevron'/Stander, and 'Robust'/Stander). It explained 61-79%, 51-76%, and 50-61% of phenotypic variation in the three populations, respectively. The fact that Morex and Harrington both contributed non-dormant alleles in previous studies and that a QTL was identified in the similar region of chromosome 5HL in the Harrington/Morex cross strongly suggests that there are at least two linked QTLs controlling dormancy in this region. |
