Maturation and conversion of somatic embryos of three genetically diverse rose cultivars

Embryogenic callus cultures of three genetically diverse cultivars of rose (Rosa hybrida L.), the floribunda 'Trumpeter', the multiflora 'Dr. Huey', and the hybrid tea 'Tineke', were used to study the effect of various carbohydrates and osmotically active compounds on somatic embryo maturation and conversion. Cotyledonary-stage embryos were produced by dispersing callus in liquid medium followed by filtration to isolate globular-stage embryos. Quantitative experiments were conducted to determine maturation and conversion of the three rose cultivars in response to medium with sucrose, glucose, fructose, or maltose as the primary carbon source and also in response to various concentrations of either myo-inositol, polyethylene glycol, or mannitol in combination with 3% sucrose. Conversion of 27% was achieved for 'Trumpeter' embryos following their maturation on 3% fructose. 'Dr. Huey' embryos required maturation on medium containing 3% sucrose supplemented with either 2.5% or 5% mannitol for 36% and 61% conversion, respectively. Maturation of 'Tineke' embryos on either 3% sucrose, 3% glucose, or 3% fructose resulted in a maximum 12% conversion.