Naser Askari

Lily is conventionally propagated by scaling: scales are detached from bulbs and kept in moistened vermiculite. These scales regenerate new bulblets. In micropropagation, scale fragments that are cultured on an artificial nutrient medium under sterile conditions, regenerate new bulblets. We have examined various aspects of lily micropropagation. Since the size of bulblets strongly influences the performance in the field, we focussed on bulblet weight. Bulblet weight strongly depended on the position in the scale from where the explant was taken (on average heavier bulblets from internal versus external positioned explants). Here, the formation of new vascular tissue within the explant likely played a role. Mild abiotic stresses administered during bulblet growth (like heat) increased the growth of bulblets by 20-65%. We also developed novel methods to reduce contamination during initiation of bulblets in vitro. These methods have already been used successfully in fruit trees. We found strong evidence that low CO2 levels during tissue culture (caused by the consumption of CO2 by active photosynthesis and the closure of tissue culture containers) is detrimental. This is because reactive oxygen species are formed in the absence of CO2 as electron acceptor.