EFFECT OF SEED NUMBER PER BERRY ON MINERAL-COMPOSITION OF GRAPEVINE (VITIS-VINIFERA L) BERRIES

In two Vitis vinifera L. cultivars, differing in susceptibility to stalk necrosis, a calcium related disease (Croatina, susceptible; Barbera, resistant), the relationship between seed number per berry and mineral concentration in the berry was investigated. Starting from the anthesis until 100 d later, weekly samples of 500 berries per cultivar were picked. Berries were divided according to their seed number and the relative percentages were: for cv. Croatina 49.3%, 38.1%, 12.6% of 1-2-3 seeded berries respectively; for cv. Barbera 31.3%, 40.4%, 23%, 5.3% of 1-2-3-4 seeded berries respectively. The berries were weighed and dried and their calcium, potassium and magnesium contents analysed. In both cultivars the final size and chemical composition of the grape berries were related to their seed number; one seeded berries were smaller than 2-3-4 seeded berries. Calcium, magnesium and potassium contents of berries increased with increasing berry seed number, but the seeds had less influence on mineral concentration per unit of berry weight. In general, calcium and magnesium concentrations decreased after veraison independently of seed number per berry, whereas potassium concentration remained constant or increased lightly. Potassium concentration in cv. Croatina berries was higher than in cv. Barbera, particularly at ripening. Calcium content increased until the berry weighed 0.8 g in cv. Croatina and 1 g in cv. Barbera, up to 0.3 and 0.5 mg per berry respectively and then remained constant until 100 d after anthesis. The final content of calcium was higher in cv. Barbera than in cv. Croatina. Potassium content in both cultivars increased during the entire period of berry growth, whereas magnesium content was affected by cultivars: in cv. Croatina it increased moderately until almost 76 d after bloom and then decreased, whereas for cv. Barbera higher content was observed before veraison (two-seeded berries), at veraison (1-3 seeded berries), and soon after veraison (four-seeded berries). Seed shaping can influence berry size and calcium, potassium and magnesium contents, with effects on must composition.