Wheat is a major world crop and as such is a primary target for improvement
of agronomic characteristics via genetic engineering. Optimization of tran
sformation is essential in order to overcome the relatively low transformat
ion frequencies encountered with wheat. Transformation of elite wheat varie
ties is not always successful due to variability in regeneration and transf
ormation frequencies between varieties. In this work, two elite wheat varie
ties with a relatively high embryogenic capacity were transformed by partic
le bombardment. A strong correlation between transformation frequency and t
he age of wheat donor plants was observed in both varieties. The mean trans
formation frequency rose from 0.7% to 5% when using immature embryos from o
ld and young donor plants, respectively. This was observed in both varietie
s, the best bombardments achieving up to 7.3% frequency. Using explants at
an optimal developmental stage from donor plants grown under environmentall
y-controlled conditions has improved the reproducibility of transformation
efficiency of elite wheat varieties and leads to the production of apparent
ly phenotypically normal, fertile, transgenic plants.