Analyses of cool climate Pinot noir vine and fruit parameters as affected by altered leaf area/crop load ratios

Abstract

The effect of vine leaf area relative to crop load was investigated in the cool climate growing region of Canterbury New Zealand using Pinot noir (clone 10/5) VSP trained vines. Three weeks after fruit set shoot leaf numbers were standardised and leaf area (LA) adjusted to 100%, 50% or 25%. Crop load (CL) was similarly adjusted, with treatments applied in a 4-replicate split plot design. The resulting LA to CL ratios ranged from 4 to 69 on average. Grapes were harvested on April 4, 2014 and a suite of analysis applied so that Canonical Variate Analysis (CVA) and Principal Component Analysis (PCA) could be used to look for treatment influences. Of the parameters measured, the following were used in the CVA analysis: Root starch, Seed dry weight, Skin weight per berry, Juice ⁰Brix, Juice pH, Citric acid, Phosphorus, Total phenolics in skin extract per berry, Tannin in skin extract per berry, Colour hue, Degree of red pigment colouration, Malvin and Kaempferol-glucoside. CVA revealed distinct groupings with 25% leaf having higher Degree of pigment colouration, Colour hue, Kaempferol glucoside and lower values for Skin weight per berry, Root starch and Seed dry weight. PCA of a subset of these variates also showed groupings by leaf level, with 100% leaf leading to higher values for Tannin in skin extract per berry, Total phenolics in skin extract per berry, Malvin, Skin weight per berry and Root starch, whereas 25% leaf was weighted towards Kaempferol-glucoside and lesser amounts of the other factors. The results suggest that there was an influence of leaf removal on fruit exposure, leading to higher flavonol concentration, but higher leaf area was responsible for greater berry skin weight, seed weight, various phenolics and stored carbohydrate. Very low LA:CL are not beneficial for fruit composition or vine health.