Transient transformation of pollen and embryogenic tissues of white spruce (Picea glauca (Moench.) Voss) resulting from microprojectile bombardment.

Detailed analyses of the physical parameters inherent in the microprojectile bombardment technology necessary to produce optimum transient β-glucuronidase (GUS) expression were undertaken in pollen and embryogenic tissues of white spruce. Higher helium pressure used for microprojectile bombardment resulted in lower GUS expression in pollen, but in higher GUS expression in embryogenic tissues. Modification of the osmoticum of the culture medium had a limited effect on GUS transient expression in pollen but substantially increased the transient expression in embryogenic tissues. The viability of transformed pollen was not affected by the bombardment procedure. This is the first detailed analysis of microprojectile bombardment technology reporting the conditions needed for optimum transient transformation of pollen and embryogenic tissues of white spruce.