Identification of vigour differences among combining pea (Pisum sativum) seed lots

Differences in field emergence of commercial combining pea seed lots (>80% germination) were revealed in field trials in 1989 (5 sowing dates, 29 seed lots, 5 cultivars) and 1991 (2 sowing dates, 26 seed lots, 3 cultivars) indicating differences in seed lot vigour. Application of laboratory tests to the lots found that no single test revealed differences in vigour for all cultivars. The laboratory germination test failed to indicate vigour differences within the combined data of all cultivars but, in contrast, the mean germination time gave the dearest identification of vigour differences. Measurement of the bulk leachate conductivity identified high and low vigour lots of two white-seeded cultivars (Consort, Countess) but the level of leakage from the marrowfat cultivar, Progreta, was lower and not related to field emergence. Analysis of leachate nitrogen content revealed similar differences and was, in same cases, superior to conductivity in revealing seed lot vigour whereas leachate carbohydrate content was not related to field emergence. Vital staining of the cotyledons with tetrazolium chloride was the best indicator of seed lot vigour in 1989 but poorer in 1991. Two tests based on seed ageing, the controlled deterioration test and assessments of K-i and the derived estimated initial germination, identified differences in seed vigour in both years when data for all cultivars was combined. However the relationships between these vigour assessments and field emergence of individual cultivars were not always significant. These data suggest that although vigour tests can identify low vigour seed tots of combining pea, it may be difficult to routinely apply a single seed vigour test to seed lots from all cultivars.