Response interactions in grape somatic embryogenic cultures to cold and gibberellic acid treatments to overcome embryo dormancy

Abstract

Somatic embryogenesis (SE) is a widely used method in grape (Vitis vinifera) biotechnology as it permits the rapid multiplication of clonal material from a single explant source. A commonly observed difficulty with this technique, however, is that many of the newly derived embryos either cease development entirely or they develop abnormally and fail to form a plantlet capable of survival beyond the in vitro environment. Previous studies have reported that somatic embryos of grape enter into a state of endodormancy similar to that seen in grape seeds. Grape seeds require a cold period of several weeks to induce germination and the release of the embryo from dormancy is associated with a rapid rise in endogenous gibberellins. We tested the influence of cold and/or a pulse treatment of gibberellic acid (GA₃) on embryogenic callus cultures of the variety Pinot noir. In the most efficient treatment tested (8 weeks in cold), a 4.6-fold improvement in plantlet recovery was recorded compared with that in the untreated controls. The improvement in yield was the result of combined increases in embryo differentiation and embryo germination. Treatment with GA₃ improved embryo germination compared to the untreated controls, but only when GA₃ was used in combination with sub-optimal cold treatments. The GA₃ pulse treatments tested had no measurable impact on embryo differentiation or on the differentiation of plantlets from young germinated embryos.