Single count of radicle emergence, DNA replication during seed germination and vigour in alfalfa seed lots

Abstract

Previous work on alfalfa seeds has illustrated the close association between the rate of germination and vigour. This study examined single early counts of radicle emergence (RE) as an indirect method to measure the rate of germination in alfalfa, and investigated cell cycle activities in the early stages of imbibition. The 6-hour interval counts of just germination (JG) and germination percentages (G) of 14 seed lots at 20, 17, 15 and 13°C were compared with final emergence and mean emergence time. Single counts of JG and G were strongly correlated with mean just germination time (MJGT), mean germination time (MGT) (P < 0.01) and field performance. The results indicate that single counts of RE after 24 hours at 20°C could be used to predic the vigour of alfalfa seeds. The embryo root tip cells of six seed lots with low, medium and high vigour were used for analysis of DNA replication by flow cytometry 3, 6, 12, 18 and 24 hours after imbibition. The 4C/2C ratio 18 hours after imbibition and the increase in 4C/2C ratio between 6 and 12 hours after imbibition was associated with the vigour of the seed lot and has the potential to predict seed vigour.