Vigor Tests Used to Rank Seed Lot Quality and Predict Field Emergence in Four Forage Species

Abstract

Laboratory and field tests were conducted in 1999 and 2000 in Gansu Province, China, to investigate the suitability of various laboratory vigor tests, to rank quality of commercial seed lots, and to predict seedling field emergence (FE) of four forage species. Species used included two legumes, purple vetch (Vicia benghalensis L.) and alfalfa (Medicago sativa L.), and two grasses, sudangrass [Sorghum bicolor (L.) Moench subsp. drummondii (Steud.) de Wet ex Davidse] and Siberian wild ryegrass (Elymus sibiricus L.). Results showed that among all tests, the electrical conductivity (EC) test provided the best estimate of seed vigor for the two legume species, both for ranking seed lots quality and predicting FE, but gave the worst indication of seed lot vigor for the two grass species. The EC result was not only poorly related to FE, but also poorly related to the standard germination (SG) of a wide range of seed lots of the two grass species that varied in viability. The controlled deterioration (CD) test generally better indicated seed lot vigor for test species than did SG, except that it lacked sensitivity in ranking seed lot quality of alfalfa and was not significantly related to Siberian wild ryegrass FE. The germination index (GI) better indicated seed lot quality and predicated FE than SG of sudangrass over the 2‐yr results, but not consistently better than SG for other species. Initial count of standard germination (SGi) generally performed more poorly than the other vigor tests. From this study and previous work on forage species, we conclude that EC test for forage legumes and CD tests for both forage legumes and grasses have the potential to be developed as improved vigor tests for ranking seed lot quality and predicting seeding performance.