Inheritance of Photoperiod Response in Barley 1

Inheritance of photoperiod response was studied in barley ( Hordeum vulgare L.). ‘Manker,’ which is relatively insensitive to daylength was crossed to four sensitive genotypes: CI 8044, ‘Steptoe,’ CI 5064, and CI 7452. The F 1 , F 2 , F 3 , and backcross generations were evaluated for photoperiod response in a short‐day environment (10 hours light and 14 hours dark). Photoperiod response was measured by the number of days from emergence to the beginning of internode elongation (identified as node at ground level, NGL). Manker required 23 days, on the average, to reach NGL, while CI 8044, Steptoe, CI 5064, and CI 7452 required 44, 57, 60, and 66 days, respectively. In a long‐day environment Manker reached NGL in 21 days, which was within the range of 19 to 25 days required for the sensitive genotypes to reach NGL. Thus the large differences observed in short days appear to be due to photoperiod sensitive genes rather than maturity genes. The progeny distributions were continuous in all generations and serve to indicate that quantitative inheritance is important in determining photoperiod response in barley. Additive effects predominated, although dominance appeared important in one cross and epistatic effects were detected in three of the four crosses. Parent‐offspring regression of F 3 family means on F 2 plants gave estimates of heritability of 0.96 ± 0.04, 0.77 ± 0.10, 0.74 ± 0.06, and 0.77 ± 0.06 in the four populations. These estimates are in good agreement with realized heritability estimates, obtained in a selection experiment, of 0.94, 0.70, 0.75, and 0.95. Although major genes were not detected, the high heritability values and the selection results indicated that breeders should have little difficulty when selecting for photoperiod response in these and similar barley populations.