PLANT-REGENERATION FROM SEEDLING EXPLANTS OF GREEN BEAN (PHASEOLUS-VULGARIS L) VIA ORGANOGENESIS

Green bean (Phaseolus vulgaris L.) plants were regenerated from 3-day old seedling explants via organogenesis. The explants contained a cotyledon and a small portion (2-3 mm) of embryonic axis split in half. Explants were cultured on a defined medium containing glutamine as the sole nitrogen source. A ring of meristematic tissue was produced at the base of the axillary bud located at the cotyledonary node. The meristematic tissue was produced only if the axillary bud was present together with the cotyledon in the explant. Buds and shoots developed from the meristematic ring. Selected shoots produced roots when excised from the cluster of buds and transferred to root induction medium. Rooted shoots (plantlets) grew well and produced viable seeds when grown in the greenhouse. Histological studies revealed the origin of buds from the peripheral layers of the meristematic ring. Production of buds and shoots was a continuous process, so that new shoots could be removed from the explant for plantlet production every 10-14 days. With the cultivar Dark Red Kidney, an average of 49 buds and 8 shoots were regenerated per explant by 30 days after culture initiation. Sixty-seven percent of the shoots produced roots, and 90-95% of the plantlets survived greenhouse acclimatization to produce healthy plants.