Assessment of soybean seed vigour tests for eastern Australia

Vigour testing was undertaken on seed from 4 soybean [Glycine max (L.) Merr.] cultivars taken from field trials in eastern Australia. The seed from each cultivar exhibited moderate to good germination and a range in vigour. Vigour tests consisted of the controlled deterioration and modified versions of the accelerated aging test. Accelerated aging was carried out in 4 ways using 2 periods of incubation (76 and 96 h), with or without the seed protectant Thiram to control saprophytic fungi. Results were compared with seedling emergence from the same seed samples when planted in a controlled environment glasshouse. A combination of 2 day/night temperatures, cold (18/13°C), warm (33/28°C), and 3 soil moisture regimes, dry (-0.3 MPa), field capacity (-0.01 MPa) and saturated soil, produced a total of 6 different environments. Emergence was also recorded under a moderate daylnight temperature of 23/18°C in soil at field capacity. The standard germination test and modified accelerated aging test with a 72-h incubation period with Thiram were significantly (P<0.01) correlated with emergence from all 7 soil environments. A 96-h period of accelerated aging (with or without Thiram) tended to suppress germination and there was no correlation with emergence from most soil environments. The controlled deterioration test correlated with seedling emergence from most soil environments except for dry soil. The vigour test which gave the best indicator of performance under a range of different seedbed moisture and temperature conditions was the modified accelerated aging test using a 72-h incubation period with Thiram.