No abstract

BackgroundCluster thinning is an agronomic practice in which a proportion of berry clusters are removed from the vine to increase the source/sink ratio and improve the quality of the remaining berries. Until now no transcriptomic data have been reported describing the mechanisms that underlie the agronomic and biochemical effects of thinning.ResultsWe profiled the transcriptome of Vitis vinifera cv. Sangiovese berries before and after thinning at veraison using a genome-wide microarray representing all grapevine genes listed in the latest V1 gene prediction. Thinning increased the source/sink ratio from 0.6 to 1.2 m2 leaf area per kg of berries and boosted the sugar and anthocyanin content at harvest. Extensive transcriptome remodeling was observed in thinned vines 2 weeks after thinning and at ripening. This included the enhanced modulation of genes that are normally regulated during berry development and the induction of a large set of genes that are not usually expressed.ConclusionCluster thinning has a profound effect on several important cellular processes and metabolic pathways including carbohydrate metabolism and the synthesis and transport of secondary products. The integrated agronomic, biochemical and transcriptomic data revealed that the positive impact of cluster thinning on final berry composition reflects a much more complex outcome than simply enhancing the normal ripening process.

Background and Aims Climate change can alter the synchronous accumulation of sugar and other main berry compounds during ripening. The aim of this study was to determine whether post‐veraison trimming could delay sugar accumulation and influence the production of anthocyanins and seed tannins in Sangiovese grapes. Methods and Results Shoots were trimmed in 2009, 2010 and 2011 when the berry total soluble solids (TSS) reached 15–17°Brix, leaving eight nodes on each main shoot. The accumulation of TSS, anthocyanins and seed tannins was measured during ripening, and yield parameters were recorded at harvest. Grapes from trimmed vines contained a lower TSS in 2009 and 2010, but there was no impact on the concentration of anthocyanins and seed tannins. In 2011, leaf area limitation was insufficient to reduce TSS accumulation, because yield constraints were observed and the leaf area/yield ratio was within the optimal range. Conclusions The lower rate of TSS accumulation in berries had no impact on the concentration of anthocyanins and seed tannins, suggesting that this approach could produce grapes with a lower TSS at harvest or delay harvest. In low‐vigour vines suffering from water deficit, the post‐veraison trimming repeated over the years could reduce yield, which may be responsible for the lack of TSS reduction compared with that of control vines. Significance of the Study Our study provides insight into the relationship between TSS accumulation and the production of anthocyanins and seed tannins in the berry in response to post‐veraison leaf area reduction.

No abstract

<p style="text-align: justify;"><strong>Aims</strong> : To test the effects of varying degrees of vigour on vine growth, cropping, grape composition and wine quality.</p><p style="text-align: justify;"><strong>Methods and results</strong>: The study was conducted in 2008-2009 in a cv. Sangiovese (<em>V. vinifera</em> L.) vineyard (Tuscany). Two uniform zones marked by low (LV) and high (HV) vigour vines were pinpointed using an NDVI (normalized difference vegetation index) map. Soil analysis showed similar texture in both zones, but total soil nutrients were lower in LV than in HV. While only LV vines showed soil water content close to wilting point in 2008, they demonstrated lower leaf area and yield and higher berry sugar and anthocyanin concentrations compared to HV vines. Chemical and wine tasting analysis of the wines made in 2009 showed that the LV wines had better sensory attributes than the HV wines, despite their excessive ethanol content.</p><p style="text-align: justify;"><strong>Conclusions</strong>: The differences in vigour, yield and must and wine quality of LV compared to HV vines were linked to variations in soil fertility and water retention capacity. Precision vineyard management practices like supplementary fertilization and irrigation should be used to increase vigour and yield and to decrease sugar content in LV grapes. Cover crop may be used in HV vines to decrease their vigour and yield.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: The study confirms that the evaluation of within-field variability is crucial for site-specific vineyard management.</p>