Dianthus gratianopolitanus Vill. 'Bath's Pink' has a near-obligate vernalization requirement

Abstract

The flowering response of Dianthus gratianopolitanus Vill. 'Bath's Pink' was characterized after varying durations at vernalizing temperatures. Genetically identical clonally propagated plants were treated at 5°C for 3, 6, 9, 12, or 15 weeks in Expt. I; at 0, 5, or 10°C for 2, 4, 6, or 8 weeks in Expt. II; and at 0, 5, 10, or 15°C for 1, 2, 4, 6, or 8 weeks in Expt. III. Dianthus gratianopolitanus 'Bath's Pink' exhibited a quantitative vernalization response after treatment at 0 to 10°C and did not vernalize after 8 weeks at 15°C, which was the longest duration tested. Complete flowering was achieved after 4 or more weeks at 0°C, 3 or more weeks at 5°C, and 8 weeks at 10°C. Based on time to anthesis and node number at anthesis, the flowering response was saturated after vernalization treatment at 0°C for 4 or more weeks and 5°C for 3 or more weeks. However, maximum flowers at anthesis were produced after 8 weeks at 0°C and 6 or more weeks at 5°C. Flowering was delayed after the 8-week treatment at 10°C compared with 6 or more weeks at 0°C and 4 or more weeks at 5°C. Based on the minimum vernalization duration required to achieve the maximum flowering response, the order of efficacy of vernalizing temperatures was 5°C > 0°C ≫ 10°C.