Oriental lily hybrids engineered to resist aphid attack

Establishing in vitro bulb scale cultures of lily cultivars followed by callusing and regeneration after gene transfer was found to be not very successful in our hands, except for ‘Snow Queen’. Identifying a more generally applicable system to generate callus with the ability to regenerate and amenable to Agrobacterium-mediated gene transfer was the goal of the research described here. Callus was induced on style and filament explants of 26 cultivars of lily. The cultivars were chosen from the hybrid groups longiflorum, asiatics and orientals of the genus Lilium but also interspecific hybrids were represented. Most cultivars were diploids but some were of triploid level and one was tetraploid. In general once callus was induced, it could relatively easily be maintained and propagated for further use. Regeneration was observed on both callus types from all cultivars tested with an efficiency ranging from 40 to 100%. Gene transfer as demonstrated by positive reporter gene uidA activity was found in all cultivars tested. Transgenic plants could be obtained in the first series of transformations and the applicability of a marker-free system was proven in lily. The protocol can now be used for the introduction of genes aiming at conferring resistance to aphids.