Biomineralogical investigation of late-harvest grapes colonised by Botrytis cinerea Pers.

Abstract

Abstract The ripening process of two grape varieties in the vineyard located in the Sandomierz region was examined. In 2015, the ‘Regent’ and the ‘Sibera’ varieties reached physiological ripeness on 30th September and 3rd October, respectively. On both harvest dates, in addition to soluble solids content, titratable acidity, and pH, the macronutrient content was also determined. In the phase of physiological ripeness, the ‘Sibera’ variety showed higher acidity (1.02 g · 100 mL−1) compared with the ‘Regent’ (0.87 g · 100 mL−1). A higher soluble solids content was found in the ‘Regent’ (20.4°Brix), and slightly lower in the ‘Sibera’ (18.1°Brix). The must of the ‘Regent’ had a higher pH (3.5). This variety also had higher macronutrient contents (K, Ca and Mg). Grapes harvested after 3 weeks (late harvest) showed higher values of sugars, pH, K, and P for both varieties. However, their titratable acidity content, and Ca and Mg contents decreased. Microscopic examination showed differences in mycelial growth of Botrytis cinerea on grape bunches for both of the varieties left for the late harvest. The mycelial growth promoted faster dehydration of the ‘Sibera’ berries. Spot chemical analyses of ‘Sibera’ berry peel performed using EDS (energy dispersive spectroscopy) showed the occurrence of elevated contents of potassium, phosphorus, sulphur, magnesium and silicon. Around skin cracks, sugar crystals as well as hard-to-identify microcrystals were formed containing potassium. On the surface of the ‘Regent’ berries, potassium, and traces of phosphorus, silicon, magnesium, sulphur and calcium were found.