Seed treatment to enhance germination of coloured lima bean (Phaseolus lunatus L.)

Abstract

Water-extractable substances cause germination problems in coloured lima beans and have also been found to inhibit the elongation of maize radicles and coleoptiles. Therefore, to break the dormancy of coloured lima bean seeds, a series of experiments was conducted with known dormancy breakers such as commercial bleach (10, 20, 30%), KNO3 (2, 4, 6%) and thiourea (2, 4, 6%). Percent germination of maize seeds and the growth of coleoptile and radicle decreased linearly as an aqueous extract of coloured lima bean was added in increasing concentrations. Commercial bleach (sodium hypochlorite), potassium nitrate and thiourea improved germination of coloured lima beans, but only 10% bleach did not inhibit the development of radicles and hypocotyls of the resulting seedlings and even increased nodulation. Seeds treated with 10% bleach for 1 h, washed and air-dried, could still germinate after 21 days of storage. It seems that any chemical treatment to enhance germination of coloured lima beans must ensure that the brown exudates are leached out, diluted or neutralized and washed away. This implies that the beans should be planted only when rains are regular and adequate.