Effect of storage on seed viability and vigour in different Ethiopian wheat and maize cultivars

English: Seed viability and vigour loss during storage, is one of the several factors limiting crop yield in Ethiopia. Ambient storage conditions (high temperature and relative humidity) as well as high moisture content during storage are considered to be the most important factors causing inferior quality of seeds (Anonymous, 1995). This supplied the rationale to study the effect of ambient temperature (more or less similar to that applying in Ethiopian conditions) and low temperature (4°C) on seed viability and vigour as well as biochemical and physiological aspects related to seed viability and vigour of Ethiopian bread and durum wheat as well as maize cultivar seeds. Additionally, the effects of storage in open and closed containers at different temperatures were also investigated. Seeds from three bread and durum wheat as well as two maize cultivars were stored at low (4°C) or ambient temperatures (18-30°C) in open or closed containers for a period of six months. Seed viability and vigour as well as biochemical and physiological aspects related to seed viability and vigour were measured before (fresh seeds) and after different storage treatments. Seed viability (germination percentage) and vigour (germination index and dry shoot mass) of seeds from both bread and durum wheat cultivars stored in open containers at ambient temperature were not significantly influenced while the other storage treatments affected the viability and vigour to various degrees. A more or less similar tendency was observed for seeds of the two maize cultivars, when only the raw data was considered. The mentioned storage condition also maintained most of the seed metabolite levels measured in this study. The lower relative humidity of the ambient storage environment contributed to maintain the moisture level of seeds at a much lower level compared to those aged at low temperature. This situation contributed to seeds aged in open containers at ambient temperature in retaining their viability and vigour during the six month storage period, indicating the need to dry seeds to a lower moisture content level before storage and/or the need for dehumidifying the storage environment, especially under Ethiopian storage conditions. Like the other two vigour tests, the measurement of electrical conductivity and the respiration rate clearly showed cultivar variations. However, they did not seem to clearly distinguish between the vigour of seeds stored under different conditions. Future work should focus towards developing a range of correlating seed vigour test methods under local conditions. In addition, the results of laboratory seed vigour tests should be correlated with field emergence in order to assess the quality of seeds with respect to its field performance potential. Biochemical tests performed in this study did not seem to correlate with the viability and vigour of seeds aged under different conditions. However, the relatively higher metabolite content of some cultivars, such as HAR-1685 (bread wheat) and E-26 (durum wheat) appeared to have contributed to their higher viability and vigour. Future research might focus on elucidating the biochemical and physiological processes underlying seed deterioration and consider developing new and cheaper screening methods for seed viability and vigour. It should also be considered to correlate future findings regarding physiological changes in stored seeds with mechanisms of seed deterioration in order to understand the mechanism of seed deterioration better in terms of biochemical process and metabolite content changes.