Transformation of wheat (Triticum aestivum L.) microspore-derived callus and microspores by particle bombardment

Twenty-seven bialaphos-tolerant and GUS-positive lines were produced from 2,940 callus pieces after particle bombardment of wheat microspore-derived callus. Regenerated plants were mainly of the albino type. In an attempt to avoid this problem, wheat microspores were used as target cells for particle bombardment. Pre-cultivation for a period of 3-8 days improved the frequency of GUS-expressing microspores. Helium rupture pressures between 1,100 psi and 1,800 psi, the amount of gold per bombardment (ranging from 37 μg to 300 μg) and particle size (0.6-1.0 μg) did not significantly affect transient expression. Microspore response measured as number of recovered embryos was not signifi- cantly affected by variations in helium pressure or amount of gold used, but response was significantly influenced by particle size. The highest number of GUS-expressing embryos was 3.5 embryos per 106 microspores, which was obtained after 4 days of pre-cultivation, 1,350 psi rupture pressure, 0.6+1.0 μm particles (1:1) and 150 μg gold particles per bombardment.