A practical method for staging grapevine inflorescence primordia in season 1, with improved description of stages

To date, scanning electron microscopy (SEM) is the only method reported for describing the stages of development of the inflorescence primordia (IP) in grapevine compound latent buds. This method has limitations, which are addressed in this paper. We propose an alternative, more practical technique that uses a dissecting light microscope to identify IP stages and record stereophotographs by digital fusion of single images taken at many sequential focusing planes. Using this technique, we examined the developmental stages of IP in the primary latent bud during season 1 in Vitis vinifera L. cv. Chardonnay by dissecting compound latent buds at monthly intervals. Our results confirm that compared to SEM preparation and imaging, this method is an easier, quicker, and minimally damaging approach for staging IP. We provide guidance for dissecting compound latent buds, and we give more detailed descriptions of IP stages 0 to 4 and new descriptions of IP stages 5, 6, and 7, which were not previously available. This work advances basic knowledge of grapevine physiology and should enhance future research involving the compound latent bud.