Forage kochia seed germination response to storage time and temperature

Abstract

The Eurasian low-shrub, forage kochia [Kochia prostrata (L.) Shad.], was introduced into western North America for use in restoration of severely disturbed landscapes in arid and semiarid environments. Seed mature in late fall and are short-lived in typical warehouse conditions. In a preliminary, cold-temperature experiment (2 degrees C) using 3-month-old seed from 16 forage kochia accessions, mean germination time, expressed as days to 50% germination, varied from 4 to 88 days. Follow up experiments using seed of 5 accessions tested the effects of storage time and temperature on seed viability and mean germination time and related this to field planting success. Sub-samples were air-dried and stored in plastic bags in a freezer, cold room, and lab (-15, 2, and 20 degrees C respectively). A fourth set of subsamples was stored in a shed with no temperature control (simulated warehouse storage). Seed were tested fresh and retested after 4, 8, 12, 24, and 36 months of storage. Mean viability decreased from 77% (range 66 to 93%) for recently harvested seed, to 24 and 8% for lab- and shed-stored seed, after 36 months of storage. No significant change in viability was observed for cold room- and freezer-stored seed. Across all accessions, cold temperature mean germination time (MGT) for recently harvested seed was 73 days (range 51 to 109 days). For each accession, germination occurred primarily over a 70 day period. Mean germination time decreased as storage time increased for lab- and shed-stored seed, varied unpredictably for cold room-stored seed, and remained unchanged for freezer-stored seed. Field germination using 1- and 2-year old lab- and shed-stored seed was significantly faster than that of same-aged cold room- and freezer-stored seed. The number of live seedlings 4 months after planting for cold room- and freezer-stored seed was 10-fold or greater than that of lab- and shed-stored seed. Thus a delayed, asynchronous cold-temperature germination pattern appears to be adaptive for forage kochia establishment. Cold, dry storage prevents loss of seed viability and preserves this desirable germination pattern.