IN-VITRO-SELECTION AND REGENERATION OF HYDROXYPROLINE-RESISTANT LINESOF WINTER-WHEAT WITH INCREASED PROLINE CONTENT AND INCREASED FROST TOLERANCE

An embryogenic callus obtained from immature embryos of a Finnish wint er wheat (Triticum aestivum L. cv. Jo 3063) was used for in vitro-sele ction of hydroxyproline (Hyp) resistant calli. Calli were plated on so lid Gamborg B5 medium containing 10 -20 mM Hyp and 2 mg L-1 2,4-D. Fro m 6018 embryogenic calli exposed to Hyp in the course of three subcult ures nine calli proved to be Hyp-resistant and remained viable and emb ryogenic. These were transferred to a regeneration medium and finally to Gamborg B5 medium before being transplanted to soil. The regenerate d plants were grown at 18-degrees-C for 6 weeks and then cold hardened at 2-degrees-C for 18 weeks. The mean osmotic potential of the Hyp-re sistant cold hardened regenerates was significantly lower than that of hardened controls. At the same time their mean proline content and th eir mean frost tolerance were significantly higher compared with regen erated controls.