The effect of pretreatment with mild heat and drought stresses on the explant and biolistic transformation frequency of three durum wheat cultivars

Abstract

The use of transgenic plants in durum wheat breeding makes possible the utilization of genes not previously available in the wheat genetic pool. However, to effectively use this technology, it is necessary to be able to continuously produce large numbers of transgenic plants. This paper describes the development of a routine biolistic transformation technology for durum wheat and its adaptation to the mass production of transgenic plants. The method involves subjecting the donor plant to mild drought stress 1 day before the transformation experiment, subsequent bombardment of the immature embryos harvested from these plants with plasmid DNA, and reduced levels of tissue culture manipulation. The in vitro culture response of bombarded immature embryos and the production of transgenic plants were investigated in three durum wheat cultivars: Mexicali, D5c31YN S74, and D5c31YN S48. In all three genotypes, immature embryos (1.0 mm long) were transformed with a plasmid containing a phosphinothricin-resistant gene (bar) under the control of the maize ubiquitin promoter. The transformation frequency was highest in Mexicali, with a range of 0–6.46% transformation efficiency. The data suggest that variations in transformation were frequently influenced by differences in the genotypes and physiological status of the donor plant, rather than by the efficiency of the particle bombardment procedure.