Does Germination Ratio Under Low Oxygen Conditions Vary Between Cultivars with Different Pre-Germination Flooding Tolerance in Soybean?.

Germination and emergence of soybean (Glycine max (L.) Merr.) are inhibited under flooding or excessive soil water conditions. It is known that pre-germination flooding tolerance varies among soybean cultivars. This inhibition is likely to be caused not only by rapid imbibition but by low oxygen (O₂) condition, but little is known on the relationship between pre-germination flooding tolerance and germination capability under low O₂ concentration. The objectives of this study were to clarify the O₂ concentration needed for germination and its relationship to pre-germination flooding tolerance. Germination ratio of five tolerant cultivars (Peking, Williams, Suzuyutaka, Hatayutaka and Aobatamame) and three susceptible cultivars (Nakasennari, Enrei and Miyagishirome) was compared under low O₂ conditions. O₂ concentration inside the germination chamber was controlled at a range of 0 - 200 mL L^-1 by mixing N₂ gas with ambient air, which was supplied through an air compressor. The inside of the chamber was maintained at 100% relative humidity and 25 ºC, under dark. Seeds were contained in the chamber with various O₂ concentrations for three days, then allowed to germinate under the ambient air conditions, and germination percentage was recorded. Germination was identified when the radicle was visible. The germination percentage of all cultivars was almost equal at the range of 200 to 80 mL L^-1 O₂ concentration. Below 60 mL L^-1 O₂ concentration, the germination was inhibited in all cultivars, and the germination percentage of susceptive cultivars was higher than Peking, indicating that pre-germination flooding tolerance in soybean is not associated with germination capability under low O₂ conditions.