Production of fertile somatic hybrid plants of sunflower and Helianthus giganteus L. by protoplast fusion

Protoplasts of Helianthus giganteus and Helianthus annuus were fused using polyethylene glycol. Before fusion H. giganteus protoplasts were subjected to iodoacetic acid treatment to render them unable to divide. Fused protoplasts were cultured in V-KM medium containing benzylaminopurine and naphtaleneacetic acid. Hybrid calli were identified on the basis of their ability of embryogenic development contributed by the Helianthus giganteus parent. Fifty embryogenic calli were cultured on MS based medium without growth regulators to induce further development of somatic embryos. Elongated shoots were removed, rooted and transferred into growth chambers. Overall morphology of the plants was intermediate between the two parents. Their hybrid nature was confirmed by chromosome counting and by the analysis of esterase isoymes. The plants flowered within two to three months and later died. Thus the perennial nature of H. giganteus is a recessive trait in this interspecific hybrid. Seeds were obtained from two of the regenerated plants. From these seeds normal fertile F2 plants could be grown.