Flowering induction in radicchio (cichorium intybus l.var silvestre bischoff):the influence of vernalization in different types and classes of precocity

Abstract

All experiments were carried out at the Experimental Station “L. Toniolo” of the University of Padova (45°21’ N; 11°58’ E). Experiment 1. This research was undertaken to study the effect of increasing duration of cold periods (0-5-10-15- 20 and 30 days) on three classes of “Rosso di Chioggia” with different precocity: “Perseo” (Precocious), “Leo” (Medium) and “Virgo” (Late). Seeds were sown on different dates (V30-V20-V15-V10-V5 and V0, i.e. May 10th- 20th-25th and 30th, June 5th and 10th 2004 respectively) and placed in pre-formed polystyrene multiple trays. Treatments with low temperatures (5 °C) started on the 1st June for V30 and for the others (V5-V10-V15 and V20) 25-20-15 and 10 days later in controlled growth chambers, while plants that did not require vernalization stayed in the greenhouse. After vernalization and its stabilisation for 15 days, plants were transplanted in open field (July 24th). Moreover, on the 30th of August the number of leaves in rosette and elongated stem on five flowered plants for each group was determined, to verify the possible existing relation between flowering and the number of leaves on plant. Experiment 2. This experiment was undertaken to compare the effect of vernalization on flowering of 8 cultivars of radicchio to assess their membership of annual or biennial species. The 8 cultivars were Rosso di Treviso tardivo “Sile tardivo”, Rosso di Treviso precoce “Mesola precoce”, Rosso di Chioggia “Perseo” (P), “Leo” (M) and “Virgo” (L), Rosso di Verona “Cologna medio”, Variegato di Lusia “Adige tardivo” e Variegato di Castelfranco “Castellano medio”. All types were vernalized for 0-5 and 15 days (V0-V5 and V15). Seeds were placed (January 15th-25th and 30th 2005 for V15, V5 and V0 respectively) in pre-formed polystyrene multiple trays. Vernalization (5 °C) started on February 14th in controlled growth chambers and, at the end, was stabilized for 15 days. After vernalization and its stabilisation, plants were transplanted in open field (May 26th). In both experiments, after the transplant, plants were controlled everyday to determine the exact day in which the stem elongation started (stage 51 BBCH). Results showed that: (1) there is no relation between the number of leaves on plant and flowering; (2) vernalization exerts different effect on promoting flowering among types; (3) on average the effect of cold period is quantitatively related to its duration; (4) low temperature increased flowering precocity anticipating the stage of phase transition; (5) the behaviour of different types of radicchio shows that Rosso di Treviso tardivo is probably a biennial plant, while the others act as annual species.