Effect of maturity stage on germination and dormancy of fresh and air‐dried seeds of bitter vetch (Vicia ervilia L.)

Abstract

Bitter vetch is an important legume crop cultivated for forage and seed yield in the Mediterranean, West Asia, and North Africa regions. Delaying seed harvest of bitter vetch may increase seed losses due to pod shattering; however, early harvest may influence seed dormancy and the ability of seed to germinate. Field experiments were conducted at two locations in Jordan to study the effect of maturity stage on germination and dormancy of fresh (before drying), air‐dried, and dry‐prechilled (at 5°C for 8 days) seeds of bitter vetch. Pods were harvested at three development stages: full‐seed pod (FS), yellow pod (YP), and brown pod (BP). Percentage of normal, abnormal, hard, and dead seeds at 14 days after planting in standard germination tests was recorded for the fresh, air‐dried, and dry‐prechilled seeds harvested at the three development stages. Germination counts of normal seedlings at 4, 7, 10, and 14 days after planting was used to calculate the germination rate index (GRI). For the fresh seeds, germination did not exceed 30% when seeds were harvested at the FS stage, and decreased to 0% at the YP stage. All non‐germinated fresh seeds harvested at the YP stage were dormant. Air‐drying and dry‐prechilling treatments improved seed germination at the YP and BP stages. Maximum germination was achieved in air‐dried and dry‐prechilled seeds harvested at the BP stage. The percentage of hard seeds was the highest for air‐dried seeds harvested at the FS stage. Percentage of hard and dormant seeds was decreased to the minimum when seeds were harvested at the BP stage and exposed to air‐drying and dry‐prechilling treatment before germination. Dry‐prechilled seeds had higher GRI than fresh and air‐dried seeds when seeds were harvested at the BP stage. In conclusion, maximum germination and minimum dormancy was achieved for air‐dried and dry‐prechilled seeds harvested at the BP stage. Dry‐prechilling treatment increased the speed of germination for seeds harvested at the BP stage. Presence of hard seeds reduced the germination of air‐dried seeds harvested at the YP stage. Bitter vetch seeds harvested at the YP stage may require scarification and a longer prechilling treatment to overcome seed dormancy observed at this stage.