Loss of seed viability in onion (Allium cepa L.) in relation to degradation of lipids during storage

Onion seeds have one of the lowest longevity among the cultivated crops as it loses viability within a year. The unmarketable seeds have no reported food value or feed value. Onion seeds contain considerable oil content which has potential industrial utility. The present study reports the changes in the quality of seed oil extracted from seeds stored for one year (2019-2020), after which the seeds were unmarketable due to low germination. The physico-chemical properties of seed oil were studied in four onion (Allium cepa L.) varieties (Bhima Safed, Bhima Super, Bhima Dark Red and Bhima Shakti) by standard analytical test. The per cent oil content varied from 12.94% - 16.02% and storage resulted in 0.64% loss in seed oil content. The mean seed germination in freshly harvested seeds was 80.50%, which declined to 52.33% after one year of ambient storage. The electrical conductivity, which measures the membrane integrity increased by 108.60% in one-year-old seeds. The physico-chemical properties of the seed oil deteriorated with the age of the seed. In comparison to the control, the acid values and peroxide values of the seed oil increased by 51.11% and 12.90% respectively, while saponification value decreased by 36.18%. Among the varieties, Bhima Dark Red had the highest degradation in the seed storability and vigour, which also had the highest deterioration in the lipid quality. The present study reports for the first time the degradation of seed lipids during ageing in onion which might be contributing to the poor storability of onion seeds.