Studies on plant regeneration from protoplasts in the genus Helianthus

Protoplasts were produced from 7-day-old hypocotyls of two cultivated sunflower genotypes and three wild sunflowers. When included in agarose droplets and cultured in TL medium supplemented with 0.1 mg/l 2,4-dichlorophenoxyacetic acid, the protoplasts gave rise to loose colonies and to "embryoids". After two months the small calli emerging from the agarose were transferred to a regeneration medium on which they grew and began to differentiate. A second transfer to the same medium 40 days later induced shoot formation on one callus of H. petiolaris. Several shoots were successfully rooted and transferred to soil where they flowered. This is the first documented report, in the genus Helianthus. of regeneration from protoplasts to fully soil-adapted plants.