Age-dependent transformation frequency in elite wheat varieties

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.