Photoperiod and temperature sensitivity in early soybean accessions from the VIR collection in Leningrad Province of the Russian Federation

The photoperiod and temperature sensitivity of the onset of flowering in 106 soybean accessions from the VIR collection has been studied for 8 years in a vegetation experiment in the conditions of Leningrad Province at 59°N, the northernmost point of soybean evaluation in the world. The accessions were previously field-assessed for the ability to form fully developed seeds in this region. The experimental conditions were extreme for soybean in terms of both photoperiod and heat supply.