ORGANOGENESIS FROM HELIANTHUS ANNUUS INBREDS AND HYBRIDS FROM THE COTYLEDONS OF ZYGOTIC EMBRYOS

Dormant mature and immature zygotic embryos of sunflower (Helianthus annuus L.) inbreds and hybrids were dissected and cultured on modified Murashige and Skoog's medium supplemented with 0.1 mg/l benzyl adenine (BA), 0.5 mg/l naphthalene acetic acid (NAA), adenine sulfate, and casamino acids. For certain inbreds and hybrids, adventitious shoot formation occurred from callused cotyledonary tissue, particularly along the cut edges. The developmental stage of the zygotic embryo was critical. Eighty percent of immature H. annuus ‘Mammoth Russian’ embryos produced adventitious shoots from cotyledons, while mature embryos did not. The organogenic potential of mature cotyledons diminished as soon as one day after germination was initiated. Different forms of regeneration were observed in two inbred lines, and when these were crossed, both forms of regeneration were observed at a lower frequency from the immature embryos of the hybrid. Rooted shoots were successfully grown to maturity in a greenhouse.