EFFECT OF TANNIN CONTENT OF FABA BEAN (VICIA-FABA) SEED ON SEED VIGOR, GERMINATION AND FIELD EMERGENCE

Differences in seed vigour of zero- and high-tannin faba beans were in vestigated using 25 seed lots of 12 cultivars following earlier report s of poor emergence in the zero-tannin types. Field emergence ranged f rom 54-96% indicating differences in seed vigour between cultivars all having high laboratory germination (> 91%). Seed from zero-tannin acc essions with poor emergence had a higher incidence of testa and cotyle don cracking, a smaller percentage of hard seeds, more rapid water upt ake, a lower percentage of vital staining of cotyledons and a greater leaching of solutes than high-tannin types. Nevertheless, variation in these characteristics existed between cultivars and lines of both typ es. Seeds with more cracks in the seed coat and fewer hard seeds imbib ed water more rapidly and consequently showed lower levels of vital st aining and more cracks in the abaxial surface of the cotyledons. Slowe r imbibition in polyethylene glycol lessened the incidence of these de leterious characteristics and may provide a practical resolution to th e problem of poor field emergence in zero-tannin lines of faba bean wi th low seed vigour.