Effect of gibberellic acid on earliness and production of hybrid and open pollinated cultivars of globe artichoke in the Campo de Cartagena (Spain)

An experiment was carried out in the Campo de Cartagena, (SE Spanish coast) to study the effect of gibberellic acid (0 and 3 applications at 20 ppm) on the earliness, yield and mean head weight of different cultivars ("Lorca", "A-106", "PSI 25000", "Nun 7144", "Nun 6374", "Nun 9444", "Nun 9409", the first three open pollinated cultivars and the others hybrids). In autumn, the open pollinated cultivars produced 1.6-2.8 t ha-1 (accumulated production up to 31 December) when untreated, rising to 6.2-9.6 t ha-1 when treated with gibberellic acid. Autumn production of the hybrid cultivars, on the other hand, was negligible without gibberellic acid treatment but reached 4.2 and 5.3 t ha-1, respectively, in "Nun 7144" and "Nun 9409" after treatment. So, autumn production figures were only comparable to those of conventional varieties in the case of the open pollinated cultivars treated with gibberellic acid. The final production figures were unaffected by treatment, the hybrids producing between 21.5 and 32.0 t ha-1 and the open pollinated cultivars between 13.3 and 14.8 t ha-1. The final yield of the hybrids was greater than that of the open pollinated cultivars and that was to be expected in conventional materials propagated by vegetative multiplication. In any case many plants of the open pollinated cultivars and of the hybrid "Nun 9409" were flattened in February. The mean weight of the heads was lower in almost all cultivars when treated with gibberellic acid.