VERNALIZATION OF EMBRYOGENIC CALLUS FROM IMMATURE EMBRYOS OF WINTER-WHEAT

Winter wheat (Triticum aestivum L.), or somaclones obtained from tissue culture require vernalization to induce flowering. The objective of this study was to compare the vernalization requirements of planted seeds of 'Norstar' winter wheat with those of embryogenic callus obtained from immature Norstar embryos. Seeds required 8 wk at 6-degrees-C (12-h photoperiod) for vernalization, after which heading occurred almost-equal-to 42 d later when grown at 20-degrees-C with an 18-h photoperiod. Vernalization of embryogenic callus required 8 to 12 wk at 6-degrees-C. Plantlets obtained from embryogenic callus flowered 8 to 9 wk after transplanting to soil, without further vernalization. These procedures eliminate the need for low-temperature growth cabinets with supplementary lighting, thus reducing the cost of producing large numbers of regenerants.