Inheritance of a Light‐Quality Sensitive Character in Soybeans1

Flowering of the soybean [Glycine max (L.) Merr.] cultivars ‘Lee’ and ‘Hill’ (insensitive to light quality) was delayed when grown in light from cool‐white fluorescent lamps at a 15‐hr photoperiod, or in natural daylight with the photoperiod extended to 15 hr by illumination with fluorescent lamps. ‘Arksoy’ and ‘Dorman’ (sensitive to light quality) flowered 28 to 30 days after emergence when grown under the same conditions. Flowering of all four cultivars was delayed when light from incandescent lamps supplemented that from the fluorescent lamps. Progeny from the crosses Dorman ✕ Hill and Arksoy ✕ Lee segregated in the F2 generation at approximately 3 delayed:1 early when grown under fluorescent lamps alone, indicating that the light‐quality sensitive character acts as a monogenic recessive under these conditions. However, when F2 populations of the same two crosses were grown in short days of natural light extended with fluorescent lamps, the heterozygote was distinguished and a 1:2:1 ratio was obtained. F1 plants from crosses between light‐quality sensitive and insensitive types had flowering dates intermediate to the parents when grown in natural light extended with fluorescent lamps, but showed a response similar to that of the insensitive parent when grown in light from fluorescent lamps alone. Reciprocal backcross data gave additional support for one locus with two alleles for the light‐quality sensitive character. Bulk populations of Arksoy ✕ Lee and Dorman ✕ Hill that had been advanced in the field were grown under fluorescent lamps. The results obtained suggest that the light‐quality sensitive genotype is a poor competitor in a mixed population.