In general terms the objectives of Work Package 2 were; seed production, breeding of plants with more rubber and the characterization of the inulin and rubber built up during the growing season. Here we focus on seed production. The aim of this activity was, starting with a small initial amount of seeds, to produce a sufficient amount of seeds needed for the agronomical test plots and the large rubber production fields in the other Work Packages. Obviously the whole TKS rubber production chain starts with the production of seeds.
TKS is an insect pollinated, outcrossing plant species and therefore seed set is dependent of transfer of pollen from one plant to the other. Pollination is performed by insects (bees, bumblebees, butterflies, hoover flies etc.). Seeds were produced in special seed production plots, also known as seed nurseries. Two types of seed production approaches were tested. First, outdoor, growing of TKS in the presence of natural pollinators. Second, indoor growing in a greenhouse only with bumblebees as pollinators. Bumblebees were provided in colonies in boxes, obtained from a commercial supplier.
Unfortunately, the outdoor nursery suffered from a unusual period of very bad weather, causing submersion and subsequent rotting of the plants. This seed nursery was considered as lost. In the greenhouse nursery TKS plants were grown in the soil, in large tents made of insect-proof mesh. A single tent contained up to 10,000 plants (figure 1 and 2). The tents kept the bumble bees inside and prevented cross pollination by other dandelions that were grown in the same greenhouse. Bumblebees turned out to be very efficient pollinators. Clearly seed production in the greenhouse is much more reliable than outdoor seed production.
Another major advantage of indoor nurseries is that much more seeds can be collected. Outdoors, large proportions of seeds will be easily dispersed by the wind, whereas in the greenhouse the delicate seed heads stay intact for at least three days. Seeds in the greenhouse could be collected with hand-held leaf sweepers. Once collected, the seeds were cleaned. First the “parachutes” of the seeds are removed by a brushing machine. Next dirt and empty seeds were removed by an air flow sorter. Finally seeds were sorted according to different seed weight into different “caliber” classes. Overall about 1.5 million TKS seeds were produced. Depending on the sowing density this is sufficient for the cultivation 3 to 15 hectare of TKS and thus satisfying the needs for the other DRIVE4EU work packages.
Figure: Early flowering of TKS in the tent in the greenhouse nursery.
Figure: First seed set in the greenhouse nursery.