Genetic Control of Photoperiod Response in Early‐Maturing, Near‐Isogenic Soybean Lines

Abstract

Photoperiod response is one factor responsible for the regional adaptation of soybean [ Glycine max (L.) Merr.] cultivars. Few photoperiod response studies have been carried out with lines containing alleles for late maturity at only one or a few loci. An understanding of the photoperiod response of early‐maturing soybean lines would facilitate cultivar development in short‐season areas. The objectives of this study were to investigate the photoperiod response of early‐maturing ‘Harosoy’ near‐isogenic lines with indeterminate and determinate growth habit and to examine the genetic model for sensitivity to natural day length extended to 20 h with incandescent lamps [incandescent long day length (ILD)]. Harosoy near‐isogenic lines were grown in the field under natural day length and ILD. The same lines were also grown in growth cabinets under 12‐ and 20‐h photoperiods with cool white fluorescent plus incandescent lamps. Under natural day length, E 3 and E 4 alleles each delayed flowering 5 d and maturity 15 d while the E 1 allele delayed both flowering and maturity ≈ 16 d compared with the alternative early‐maturing alleles. The E 3 and E 4 alleles each delayed flowering 30 d under ILD compared with natural day length. The E 1 allele did not delay flowering or maturity under ILD compared with natural day length. Under 12‐h days in a growth cabinet, there were no differences among near‐isogenic lines for flowering or maturity, but the loci responded differently in the 20‐h photoperiods. The E 3 allele exhibited the largest photoperiod response, delaying flowering 24 d and maturity 84 d, compared with 12‐h photoperiods. These photoperiod‐sensitivity loci produced differential photoperiod responses that may he useful for short‐season cultivar development.