Articles
SELECTION FOR EARLY FLOWERING IN BLUE STATICE – (LIMONIUM SINUATUM MILL.)
It is commercially grown as an annual cut-flower crop in many parts of the world and is used for both fresh and dry flower arrangements.
In its natural habitat, the seeds germinate in the fall following the early rain, producing flat rosettes.
The plants remain in the vegetative rosette stage until their vernalization requirement is fulfilled and bolting is induced.
Thus, plants which are naturally vernalized produce their flowers in the spring and throughout the summer.
The cultivated statice, grown mainly as a summer crop, flowers following a similar course of events to that in a natural population.
Israeli growers export flowers to the European markets during the winter months.
In order to induce flowering in the winter, seedlings of statice have to be vernalized for 8 weeks prior to the planting in the field in mid-August.
However, high temperatures during the planting season in Israel often cause the plants to devernalize and delay flowering to the spring, when market prices drop sharply due to the abundance of flowers from naturally vernalized plants. Limonium sinuatum is a mandatory cross-pollinator and, therefore, a genetic variation exists in both commercial and natural populations with respect to both the level of vernalization needed for flowering and the rate of flower production.
This variation served as the basis for a breeding program which aimed to select statice plants requiring lower levels of vernalization or no vernalization at all for flowering.
Such plants should retain above-threshold levels of the vernalization stimulus even after an exposure to high temperatures during planting in the field, enabling them to flower early despite the devernalization.
The procedure followed the following steps: 1) Seedling populations of blue statice were exposed to 11°C for 1 week: 2) individual plants which responded to the treatment by flowering early and producing many flowers were selected and allowed to cross-pollinate with the entire population of selected individuals: 3) seeds were collected from the selected seed-producing parents and planted as half-sib families in the following season: 4) recurrent selection was applied between and within families for five generations.
Finally, seed samples of all selected families were lumped to produce a synthetic cultivar.
The response of the selected population to vernalization following 5 years of selection was compared with that of the original population.
Non-vernalized plants of the selected strain flowered 3 months earlier than those of the original population which had received the same treatment, and had similar yield curves to those of the non-selected population that had been exposed to 6 weeks of vernalization treatment.