The Effect of Seed Treatments on the Germination of Fresh and Stored Seeds of Okra (Abelmoschus esculentus) and Water Spinach (Ipomoea aquatica)

Okra and water spinach are traditional vegetables that are vital for healthy diets. Major variations in germination response have been observed among genebank entries. This study was undertaken to elucidate the effect of various seed treatments on the germination of fresh and stored seed of okra and water spinach. Freshly harvested fruits of two okra and two water spinach accessions with contrasting geographical origin and breeding status were dried in a screenhouse prior to manual seed extraction and cleaning. Cleaned seeds were dried to 6% seed moisture content in a dehumidified drying room. Various seed treatments were conducted after a 6-month storage period at 5oC and -15oC. Our studies confirmed previous results that both okra and water spinach are difficult to germinate and to obtain good field establishment due to physical, seed coat-imposed dormancy. Moreover, significant genotypic variation among genebank entries/cultivars was found for both crops, making germination response difficult to predict. Improved varieties showed much better germination response than landraces and did not require seed treatments for satisfactory germination. Hydropriming, i.e. soaking of seed in water for 24 hours, did not have an impact on seed germination. Partial removal of the seed coat, followed by 24 hours soaking in water consistently resulted in high germination percentages (>80%) of genotypes of both crops that had not undergone dedicated breeding (landraces), under laboratory and screenhouse conditions and during two subsequent growing seasons. When distributing seed samples of semi-domesticated accessions or landraces, genebanks should advise seed recipients that scarification methods may be necessary to obtain satisfactory seed germination and field establishment.