Effects of loci determining photoperiod sensitivity (Ppd-H1) and vernalization response (Sh2) on agronomic traits in the 'Dicktoo'×'Morex' barley mapping population

The objectives of this research were to determine the individual and interaction effects of the Ppd-H1 and Sh2 loci on agronomic traits under short- and long-photoperiod regimes. Nineteen doubled haploid (DH) lines from the ‘Dicktoo’בMorex’ mapping population, which represented the four genotypes at the Ppd-H1 and Sh2 loci, were pheno-typed in controlled environment photoperiods. Both Ppd-H1 and Sh2 had significant effects on several agronomic traits, in addition to their role in determining first node appearance and flowering time. The magnitude of these effects depended on daylight. Under long-day conditions (18 h) Ppd-H1, and under short-day conditions (12 h) Sh2 was a significant determinant of most characters. The interactions between these two loci were significant for several characters, particularly for yield components, under both long- and short-photoperiod regimes. Under the long-day treatment, Ppd-H1 influenced plant height through the determination of node number. There was an epistatic association between the two loci for both 1000-kernel weight and tillering. The combination of photoperiod insensitivity and vernalization requirement caused a significant increase in tillering. This was paralleled by a decrease in 1000-kernel weight. Under the long-day treatment, neither Ppd-H1 nor Sh2 influenced plant yield. Under short-day conditions, the combination of photoperiod insensitivity and vernalization requirement had a pronounced negative effect on plant yield.