Sensorial, biochemical and molecular changes in Raboso Piave grape berries applying "Double Maturation Raisonnée" and late harvest techniques.

At ripening, Vitis vinifera cv Raboso Piave grapes have high acidity, which results in an astringent wine that is not easy to drink. To overcome this limitation, several researches have attempted to alter the polyphenols profile mainly by applying different harvest techniques. The aim of this work was to investigate sensorial, biochemical, and molecular changes in Raboso Piave grape berries subjected to delayed harvests as Late Harvest (LH) and "Double Maturation Raisonnée" (DMR) techniques. At the molecular level, a microarray study was conducted comparing Traditional Harvest berries (TH) to LH and DMR ones. Gene ontology enrichment analysis pointed out that LH and DMR techniques affected metabolism of acids, sugars and polyphenols. A Principal Component Analysis, performed on transcriptomic data, pointed out that malate catabolism as well as some branches of flavonoids biosynthesis are significantly affected by DMR. In DMR grape berries, the flavonol and catechin accumulations were induced and depressed, respectively. In parallel, the transcription of flavonol synthase and leucoanthocyanidin-reductase 2, the main genes responsible for flavonol and catechin biosynthesis, were similarly induced and down-regulated. These changes resulted in a brighter colored wine with lower astringency.

Silencing leaf sorbitol synthesis alters long-distance partitioning and apple fruit quality.

Sorbitol and sucrose are major products of photosynthesis distributed in apple trees (Malus domestica Borkh. cv. "Greensleeves") that affect quality in fruit. Transgenic apple plants were silenced or up-regulated for sorbitol-6-phosphate dehydrogenase by using the CaMV35S promoter to define the role of sorbitol distribution in fruit development. Transgenic plants with suppressed sorbitol-6-phosphate dehydrogenase compensated by accumulating sucrose and starch in leaves, and morning and midday net carbon assimilation rates were significantly lower. The sorbitol to sucrose ratio in leaves was reduced by approximately 90% and in phloem exudates by approximately 75%. The fruit accumulated more glucose and less fructose, starch, and malic acid, with no overall differences in weight and firmness. Sorbitol dehydrogenase activity was reduced in silenced fruit, but activities of neutral invertase, vacuolar invertase, cell wall-bound invertase, fructose kinase, and hexokinase were unaffected. Analyses of transcript levels and activity of enzymes involved in carbohydrate metabolism throughout fruit development revealed significant differences in pathways related to sorbitol transport and breakdown. Together, these results suggest that sorbitol distribution plays a key role in fruit carbon metabolism and affects quality attributes such as sugar-acid balance and starch accumulation.

Apple (Malus x domestica).

Apple (Malus x domestica) is one of the most consumed fruit crops in the world. The major production areas are the temperate regions, however, because of its excellent storage capacity it is transported to distant markets covering the four corners of the earth. Transformation is a key to sustaining this demand - permitting the potential enhancement of existing cultivars as well as to investigate the development of new cultivars resistant to pest, disease, and storage problems that occur in the major production areas. In this paper we describe an efficient Agrobacterium tumefaciens-mediated transformation protocol that utilizes leaf tissues from in vitro grown plants. Shoot regeneration is selected with kanamycin using the selectable kanamycin phosphotransferase (APH(3)II) gene and the resulting transformants confirmed using the scorable uidA gene encoding the bacterial beta-glucuronidase (GUS) enzyme via histochemical staining. Transformed shoots are propagated, rooted to create transgenic plants that are then introduced into soil, acclimatized and transferred to the greenhouse from where they are taken out into the orchard for field-testing.

Effect of down-regulation of ethylene biosynthesis on fruit flavor complex in apple fruit.

The role of ethylene in regulating sugar, acid, texture and volatile components of fruit quality was investigated in transgenic apple fruit modified in their capacity to synthesize endogenous ethylene. Fruit obtained from plants silenced for either ACS (ACC synthase; ACC-1-aminocyclopropane-1-carboxylic acid) or ACO (ACC oxidase), key enzymes responsible for ethylene biosynthesis, expectedly showed reduced autocatalytic ethylene production. Ethylene suppressed fruits were significantly firmer than controls and displayed an increased shelf-life. No significant difference was observed in sugar or acid accumulation suggesting that sugar and acid composition and accumulation is not directly under ethylene control. Interestingly, a significant and dramatic suppression of the synthesis of volatile esters was observed in fruit silenced for ethylene. However, no significant suppression was observed for the aldehyde and alcohol precursors of these esters. Our results indicate that ethylene differentially regulates fruit quality components and the availability of these transgenic apple trees provides a unique resource to define the role of ethylene and other factors that regulate fruit development.