The suitability of the PMI-based system for efficient gene transfer in grape was assessed on V. vinifera 'Bra-chetto' and 'Chardonnay' and the rootstock '110 Rich-ter'. The effect of mannose on non-transformed tissues was evaluated during a long culture period in the crucial stages of morphogenesis from callus to plantlet. Grape tissues of the genotypes used were affected by mannose as the carbohydrate source, damage, however, appeared after extremely long culture times. In addition , plantlets

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... were regenerated from embryogenic calli after co-culture with Agrobacterium LBA 4404 carrying the manA gene in the PMI-GUS-Intron plasmid based on the pNOV2819 vector by Syngenta (Positech® system). Plants recovered after selection in the presence of mannose were found to be non-transgenic for the manA gene. Accordingly, PMI seems to be an unsuitable alternative to traditional marker gene selection for successful gene transfer in grape. K e y w o r d s : V. vinifera, positive selection, man-nose, PMI, marker genes. A b b r e v i a t i o n s : 2,4-D = 2,4-dichlorophenoxyacetic acid; BA = 6-benzyladenide; Fw = forward primer; GUS = β-glucuronidase; IAA = in-dole-3-acetic acid; NAA = 2-naphtoxyacetic acid; PMI = phosphomannose isomerase; Rv = reverse primer.