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We used the ‘Baronesse’/‘Full Pint’ doubled haploid population to analyse the genetic factors controlling flowering date under South American conditions. Both parents have similar heading dates, but the population shows transgressive segregation. Two genes, eps2S on chromosome 2H and sdw1 on chromosome 3H, explained most of the phenotypic variation for anthesis date, with the later allele carried by ‘Baronesse’ and ‘Full Pint’ , respectively. Both effects were completely additive with no interaction. We studied three plant developmental periods: seedling emergence to tillering (Z10–Z20), tillering (Z20–Z30) and end of tillering to anthesis (Z30–Z49) under field conditions at three contrasting planting dates. Z10–Z20 was also measured under semi-controlled conditions. eps2S controlled Z30–Z49 periods, while sdw1 controlled Z20–Z30. Each of the two genes for the end-point phenotype—anthesis date—was a determinant of flowering at a different developmental stage. No gene x planting date interactions were detected.

Quantitative trait loci (QTL) analysis can contribute to a deeper understanding of crop phenology. The parents of a barley mapping population have similar growth and development profiles, but the progeny show transgressive segregation for phenological traits. These phenotypes were measured in eight field experiments, using different planting dates over 3 years. Five QTL, on four chromosomes, were detected for anthesis date. The four maturity QTL were on the same chromosomes as the anthesis QTL. Five QTL for grain filling were detected on all chromosomes. Three QTL, on chromosomes 1H and 2H, were detected for photoperiod sensitivity. Both parents contributed higher value alleles for all traits, except for photoperiod sensitivity. QTL epistasis was not significant. Two QTL explained most of the phenotypic variation for anthesis and physiological maturity. Non-parental combinations of alleles at these loci account for the phenotypic transgressive segregation. Candidate genes for these QTL effects are eps2S (2H) and denso (3H). QTL for other traits had smaller effects and were coincident with genes and/or QTL for the same traits reported in other germplasm.