The effects of proline, thioproline and methylglyoxal-bis-(guanylhydrazone) on shoot regeneration frequencies from stem explants of B. napus.

Internode segments from aseptic shoot cultures are the most prolific explants for the regeneration of Brassica shoots in vitro. These explants also have the advantage of not being subject to the genotypic variations in regeneration response observed in hypocotyl and cotyledon explants. Despite reports of 80-100% shoot regeneration from stem explants, observed frequencies are typically 50-60%. Three media additives, proline, thioproline and methylglyoxal-bis-(guanylhydrazone) (MGBG), were tested for their efficacy in promoting shoot regeneration from stem explants of two B. napus varieties, Westar and Cobra. The effects of proline and thioproline on both varieties were neutral or deleterious. In Cobra the MGBG treatments caused a uniform reduction in explant regeneration. However, at low concentrations (0.35μM) MGBG resulted in a 50% increase, to 92%, in regeneration from Westar. The potential of MGBG in promoting explant regeneration in B. napus is discussed in the light of its interaction with the explant genotype.