Seed pelletizing in tobacco provides improved seed handling for seeding. The amount of pelletized seed remaining after seeding can be quite substantial in certain cases, requiring proper storage if the seed is to be seeded the subsequent year. To minimize the deterioration of leftover seeds it is crucial to store the seeds under optimum conditions. The objective of this study was to determine the best storage environments that would maintain the viability of pelleted seed.
Two seedlots of tobacco (2011 grown CT157 and 2014 grown CT652) both pelletized in the U.S. in early 2015 were stored for periods of 1 and 2 years in 1.) a freezer (-18.0oC), 2.) a refrigerator (4.0oC), 3.) a seed room (18oC), 4.) an office (21-23oC) in a filing cabinet (office location 1), and 5.) in the same office as in treatment 4 (21-23oC) but on a book shelf (office location 2). Each seedlot was stored in small plastic containers with lids and sealed with one exception. The seeds stored on top of the book shelf were in sealed Petri dishes. The seedlots were examined for germination before being stored and after each storage period.
The pre-storage germination at 10 days after incubation was 84.5 to 92% with a mean of 88.3% for the two seedlots.
After one year of storage, seeds stored in the office showed the slowest germination, monitored at 7 days after incubation, with this tendency being more apparent in one seedlot than the other, but no statistical differences were found among storage methods in the final germination percentages at 10 days after incubation. The germination rate index (GRI) (higher value indicates more seed vigour) for seeds stored by the different methods ranged from 5.9 (office location 2) to 6.2 (freezer and refrigerator) compared to the average pre-storage GRI value of 7.2.
After 2 years of storage, statistical differences were found among storage methods at all germination counting dates. The germination percentage from the first counting at 7 days after incubation was the highest with the freezer (82.2%) and refrigerator (80.8%) storages and considerably lower for the seed room (54.8%), office location 1 (52.0%) and office location 2 (34.0%). The superior germination observed at the first germination counting date for seed stored in the freezer and refrigerator generally resulted in numerically higher final germination percentages and higher germination rate indices.
Seeds stored in the freezer and the refrigerator for 2 years showed 88.8% and 86.5% germination respectively, at 10 days after incubation, which were just as much as the pre-storage seed germination at 10 days after incubation (88.3%). Storage with the other methods showed 71.2% (office location 2) to 84.0% (seed room) germination at 10 days after incubation after the 2 years of storage. The GRI for all the storage methods ranged from 6.3 (freezer) to 4.5 (office location 2).
Temperatures in the different storage environments seem to account for the differences in the germination percentages observed. Overall, storing pelletized seed in a freezer or refrigerator appears to be the best option to maintain as much seed germination and seed vigour as possible. The seed must be stored in sealed waterproof containers to keep out moisture, a major cause of rapid deterioration in seed viability and vigour. Ordinary room temperature storage may be associated with slower germination, and this can result in non-uniform plants and adversely impact the amount of usable transplants.
The full report on this study can be found in the Plant Breeding section of this website.
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