Influence of Malolactic Fermentation on the Quality of Riesling Wine

Biotic and abiotic stress has a negative effect on both the quality and quantity of grape production. Like many woody crops, grape has been relatively recalcitrant to in vitro manipulations. The crucial point in the process of genetic transformation is to have cells that are able to both regenerate and be transformed. A regeneration system seems to be a major problem in the transformation process. Somatic embryogenesis is the favoured regenerative protocol in genetic transformations of grapes. Comparison of an embryogenic and organogenic system in grape demonstrated that organogenesis frequently leads to chemical transformation of tissues. In this respect we started to develop and apply procedures suitable for the genetic transformation of grapevine. Two sources of explants were used for embryo induction. In the first case, immature zygotic ovules of Vitis vinifera seedless genotypes were used. In the second case in vivo leaf tissues from rootstocks Vitis rupestris cv. Rupestris du Lot and 110 Richter (Vitis berlandieri x Vitis rupestris). Continual transfer to fresh medium maintained embryogenic cultures. Agrobacterium tumefaciens mediated transformation of enbryogenic cultures of seedless grapes (Vitis vinifera L.) with constructs containing the gene encoding the coat protein of Grape Fanleaf Virus (GFLV) and with four constructs containing genes encoding for an antifreeze protein. An embryogenic culture of rootstock Vitis rupestris cv. Rupestris du Lot was transformed with a construct carrying the bete-glucoronidase (GUS) gene. The first transformed plantlets have been regenerated from somatic embryos and the presence of the NPTII gene was verified by PCR and Southern blot analyses