Head growth parameters of globe artichoke as influenced by genotype and temperature

The aim of this paper was to analyse and to compare the head (inflorescence) growth of different globe artichoke cultivars and time of head initiation. The study was conducted in a field along the coastal plain area south of Siracusa (Sicily) using five cultivars: Violetto Margot, 'Violetto di Sicilia clone MO 10' and 'Terom' with long shaped heads and 'Blanc Hyerois' and 'Romanesco' with spherical heads. About 200 main heads were marked and maximum width and length measured with callipers. Measurements were made weekly from head growth stage 'A' (when head is toucheable inside the rosetta) to stage 'D' (when heads are at marketable maturity and flower buds are 3-4 mm long), which is representative of marketing stage regardless of size. The head growth pattern was linear for all cultivars. The growth rate resulted higher in 'Romanesco' and 'Terom' heads, intermediate in 'Violetto di Sicilia clone MO 10' and 'Violetto di Margot' and lower in 'Blanc Hyerois'. Heads of 'Romanesco' and 'Blanc Hyerois', after stage 'A', grow homogeneously in a radial direction, whereas heads of 'Violetto di Sicilia clone MO 10', 'Violetto Margot' and 'Terom' showed a linear and significant decrease in length/width ratio over the time. The seasonal period of initiation of heads (stage 'A') affected its growth rate, which was highest in March and lowest in January.