Single count of radicle emergence and mean germination time estimate seed vigour of Chinese milk vetch (Astragalus sinicus)

This research explored the relationship between a single count of radicle emergence (RE) and mean germination time (MGT) with seed vigour for Chinese milk vetch (Astragalus sinicus) (CMV), a globally important legume used as a forage, green manure, and rotation crop. Fourteen seed lots of CMV were used to determine standard germination (SG), RE and MGT in the laboratory. Field experiments were conducted at two sites to measure the emergence performance including field emergence (FE), seedling dry weight (SDW) and simplified vigour index (SVI). The SG ranged from 89.0 to 95.5% and was not significantly correlated with field performance at either of two sites. However, both a single count of RE at 20 hours and MGT were highly predictive of FE, SDW and SVI at both sites (R-2 ranged from 0.612 to 0.897 for RE; 0.604 to 0.870 for MGT). The RE was positively related to field performance while MGT was negatively related. The seed lots with lower RE at 20 hours had lower FE and higher MGT. Overall, both RE at 20 hours and MGT are suitable indices for the vigour evaluation of CMV. However, a single count of RE is more accurate, quick and convenient.