Breaking hard seed dormancy in diverse accessions of five wild Vigna species by hot water and mechanical scarification

Abstract

The suitability of different scarification pretreatments, including immersing seeds in hot water at 80 C for 3, 6, 9 or 12 min, covering with boiling water then cooling at room temperature for 2 hours, scarifying seed between sand paper and chipping the seed coat using sharp forceps, were studied to break hard seed dormancy in 18 seed lots of 14 accessions of the wild Vigna species: V. membranacea, V. oblongifolia, V. racemosa, V. schanperi, and V. vexillata. The average hard seededness for all samples was 53% ranging from 14% to 99% within lots and species. With a few exceptions all pretreatments reduced hard seed percentage and increased final germination percentage significantly (P < 0.05) compared to untreated seeds. Response to different pretreatments varied among species, accessions or seed lots, but the majority of samples had similar responses to the pretreatments. Taking the mean of all samples into account, the best pretreatment was chipping the seed coat. This decreased hard seeds to zero and maximum germination was reached after 3 days incubation. The effects of other pretreatments were generally similar, reducing hard seed to 9% (6 - 13%) and increasing final germination from 36% before pretreatment to 78% (75 - 81%), with the maximum germination reached at the end of a 2 week test period. Germination rates of seeds pretreated with sand paper scarification were generally higher than those following pretreatment with hot and boiling water. More abnormal seedlings/dead seeds were found from hot water pretreatments for 9 min and 12 min compared to other pretreatments for some lots.