Effect of air-drying immature seeds in harvested pods on seed quality of common vetch (Vicia sativa L.)

Immature seeds of common vetch had low germination and were desiccation sensitive when seeds were extracted from pods before drying. Air-drying immature seeds in harvested pods may improve their germination and vigour. The objective of this experiment was to study the effect of air-drying immature seeds in harvested pods on seed germination and vigour of common vetch and to identify the vigour test that best discriminates seed vigour differences amongst seeds harvested at different maturity stages and drying treatments. Seeds of common vetch were harvested at five pod developmental stages: beginning of seed fill (BS), full-size seed (FS), greenish-yellow pod (GY), yellow pod (Y), and brown pod (B) and subjected to three drying treatments: seeds dried after extraction from pods (depodded), dried in pods detached from plants (podded detached) or attached to plants (podded attached). Seed germination and seed vigour, as estimated by the germination after three accelerated ageing (AA) treatments and by electrical conductivity of seed leachate, were evaluated for the harvested seeds. Seeds were subjected to three ageing treatments (100% RH and 39 degrees C for 72 h, 39 degrees C for 96 h, or 45 degrees C for 48 h) to identify the AA treatment that best discriminates seed vigour differences amongst common vetch seed lots. Podded dried seeds detached from or attached to plants had higher standard germination, germination after three accelerated ageing treatments, and lower electrical conductivity of seed leachates than depodded dried seeds when seeds were harvested at the BS and FS stages of development. Although the podded dried immature seeds did not differ significantly in standard germination from the podded dried mature seeds, the podded dried immature seeds had lower vigour as estimated by the germination after 39 degrees C for 96 h. Seed ageing at close to 100% relative humidity and 39 degrees C for 96 h was the best condition to separate the differences in vigour among maturity stages and drying treatments. The 39 degrees C for 96 h treatment can be a useful test to assess seed vigour of common vetch and needs further evaluation.