Effect of drying methods on germination and dormancy of common vetch (Vicia sativa L.) seed harvested at different maturity stages

Common vetch seeds acquire the germination capability at specific developmental stage. Post-harvest seed drying may affect seed desiccation tolerance and seed germination and dormancy. A field experiment was conducted to study the effect of drying methods on seed germination and dormancy of common vetch harvested at different maturity stages. Plants were harvested at five pod developmental stages: beginning of seed fill (BS), full-sized seed (FS), greenish-yellow pod (GY), yellow pod (Y) and brown pod (B). Seeds of the harvested plants were dried at ambient condition (28 degrees C +/- 2) using three methods: either seeds were dried after extraction from pods (depodded seeds), or seeds were dried within pods detached from plants, or seeds were dried within pods attached to plants. Seed moisture content was recorded during the drying treatments. Seed dry weight was measured both before and after applying the drying treatments. Standard germination and speed of germination (as estimated by germination rate) were assessed. Seeds harvested at BS and FS stage and dried after extraction had significantly lower final germination (< 55%) and rates and higher dormancy than seeds harvested at GY, Y and B stages. This indicated that depodded dried seeds acquired the maximum germination capability when seeds were harvested at GY stage (slightly prior to seed physiological maturity). Seeds drying within pods detached or attached to plants improved final germination (> 92%), germination rate and reduced the percentage of dormant and dead seeds and abnormal seedlings when seeds were harvested at the BS and FS pod stages. This indicated that after-ripening of seeds within pods reduced seed dormancy and improved seed desiccation tolerance, germination and GRI when seeds were harvested at immature stages. Seeds harvested at or after GY stage attained the maximum germination (> 95%) with no significant differences among the drying treatments.