Frequent individual counts of radicle emergence and mean just germination time predict seed vigour of Avena sativa and Elymus nutans

Single early counts of radicle emergence (RE) and mean just germination time (MJGT) have been used to estimate seed vigour for several vegetable and crop species. The objectives of this study were to test the suitability of these two methods for determining seed vigour of two important forage grass species, Avena sativa and Elymus nutans. Fifteen seed lots each of A. sativa (standard germination (SG) ranged from 80 to 93%) and E. nutans (SG from 70 to 84%) were used to determine MJGT and RE in the laboratory. Field emergence (FE) and mean field emergence time (MET) were evaluated at two sowing dates in April and May 2014. SG was not significantly correlated with FE at either of the two sowing dates. However, for both species, MJGT was significantly positively correlated with both MET and FE. Thus seed lots with rapid germination (low MJGT) also emerged rapidly (low MET) and to a higher value than lots that germinated slowly (high MJGT). A single count of radicle emergence (RE) taken after 52 hours at 20°C for A. sativa and 76 hours at 25°C for E. nutans was predictive of MJGT (R ² = 0.94 and 0.62, respectively) and of field emergence at both sowings for both species (R ² = 0.62 at sowing 1 and 0.63 at sowing 2 for A. sativa; 0.67 at sowing 1 and 0.64 at sowing 2 for E. nutans). RE was also correlated with MET in E. nutans, but not A. sativa where there were only small differences in MET. We suggest RE and MJGT are both suitable indices for assessing field emergence and hence seed vigour of the two forage species.