Effects of gibberellin and cytokinin on phenolic and volatile composition of Sangiovese grapes

Cytokinin and gibberellin are plant growth regulators (PGRs) used to increase berry size in seedless table grapes but their effects on wine grape phenolics and volatiles was not studied. In the current study, gibberellic acid (GA3) and synthetic cytokinin forchlorfenuron (CPPU) and their combination were applied to fruitlets of Sangiovese and berries were sampled 79 days following application. All the treatment significantly increase berry diameter and berry weight and CPPU containing treatment increased skin thickness. All treatments reduced sugar accumulation and color development but did not have an effect on acid levels. HPLC analysis showed that total flavan-3-ols level was increased by CPPU, GA containing treatments reduced the levels of flavonols and anthocyanins were significantly reduced in all the treatment (asymptotic to 50%). Phloroglucinol analysis showed that proanthocyanidins level were significantly increased whereas the mean degree of polymerization was reduced from 40 to asymptotic to 21 by all the treatments. GC-MS analysis of berries showed a decrease in fatty acid derived volatile compounds by all treatments with potential impact on flavor. Analysis of wine phenolics in subsequent harvest was in general agreement with the previous results. In summary, this study provides new information on how PGRs can change berry composition and subsequently wine attributes.