Interactive role of ethylene and polyamines on shoot regenerabillty of Chinese kale ( Brassica alboglabra Bailey) in vitro

Abstract

Summary The regulatory role of ethylene and polyamines (PAs) on shoot regeneration of Chinese kale ( Brassica alboglabra Bailey) grown on medium solidified with different gelling agents was investigated. Among the 4 gelling agents tested, medium solidified with 0.4 % agarose was the most effective in shoot regeneration. Shoot regenerability was further enhanced by incorporation of inhibitors of ethylene biosynthesis and action (25 μmol · L −1 aminoethoxyvinylglycine (AVG) or 10 μmol · L −1 AgNO 3 ) in the medium. AVG decreased ethylene production during the first week of culture, whereas AgNO 3 markedly stimulated ethylene synthesis. The promotive effect of AVG on shoot regeneration was overcome in the presence of 100 μmol · L −1 exogenous 1-aminocyclopropane-1-carboxylate or 2-chloroethylphosphonic acid, while AgNO 3 -enhanced regeneration was only slightly affected by these chemicals. Application of difluorometh-ylarginine at ≥0.1 mmol · L −1 also suppressed ethylene inhibitor-enhanced regeneration, however, growth could be restored by application of 10 mmol · L −1 putrescine. Difluoromethylornithine had no effect on shoot regenerability of the expiant. Apart from ethylene inhibitors, regenerability was also enhanced by exogenous application of 5–20 mmol · L −1 putrescine, 0.75 mmol · L −1 spermidine or 0.075 mmol · L −1 spermine, but ethylene synthesis of the expiant was not affected by exogenous PAs. The level of α-naph-thaleneacetic acid (NAA) in the medium was important to shoot regeneration, which occurred at a high frequency at 1 mg · L −1 NAA in combination with 2 mg · L −1 benzyladenine, despite the absence or presence of ethylene inhibitor. NAA at concentrations lower than 1 mg · L −1 was inhibitory to regeneration, although it stimulated ethylene production.