Mother plant material

The process, shown in Figure 1, starts (F0 in Figure 1) with highly indexed, virus free plant stock varieties conserved at the RAC lab. The Erntestolz, Hermes, Agria, Eba, Desiree, Nicola, Urgenta, Ditta and Ostara varieties have all been produced as potato microtubers.

Both Dr. Page and the RAC lab use Osmotek’s tall, 700536 vessel bottoms, with the 750547 vented lid to eliminate the effects of ethylene and achieve healthy plant growth on agar medium (Figure 2).

The plants on tuberization medium are placed in a refrigerated growth chamber (Figures 5 and 6). By carefully controlling the medium replacement frequency, light cycle, and other growth parameters, after about two months the plants produce an average of 15 to 25 microtubers per box with a diameter of 12 – 15mm.

Generation of Virus-free Minitubers

To maintain the plants in a disease free condition during the multiplication stage and generation of minitubers, the microtubers are planted in plastic boxes filled with a special artificial soil mixtures (Figures 8 & 9). These boxes are then placed under net tunnels in the field with controlled irrigation.

Dr. Page is quick to point out that while the LifeGuard vessels are relatively expensive compared to many other alternatives. However, their height, optical clarity and most importantly, their vented lids, create a contamination free atmosphere for plants with great leaf and strong root systems. His vessels are almost eight years old, and yet, as the pictures show, they do not look the worse for wear, even though they have gone through an average of 32 autoclave cycles.

This type of vessel life enhancement is at least partly due to the use of a liquid medium growth system, which is much easier in its cleaning cycle on the polycarbonate plastic. Agar is much more difficult to remove, and the chemicals and higher cleaning temperature slowly attack the plastic, causing it to become cloudy. The cost of cleaning the vessels is also significantly reduced with liquid medium, since it is simply poured out and the vessel is washed in an ordinary dishwasher, with mild detergent and a low temperature cycle.

The liquid medium based growth system uses 25 micron membrane rafts, which are part of the cost of a plant growth cycle and microtuber harvest, since the roots grow into the membrane. Since he purchases a 4 year supply of membrane rafts at one time (about 20,000 units), he benefits from a significant volume discount, and lowered cost of shipping and handling. These contribute about US$0.03 to the cost of a microtuber, which is about 2% of the total cost of production.

Despite the relatively high costs of microtuber production, the vigor and growth they display in the conventional multiplication steps more than make up for this cost. Each microtuber creates 4-6 plants, and about 25 excellent quality minitubers. This leverage is what makes the entire process so competitive and worthwhile.

There’s also no question that the technique can be used to greater advantage in lower labor cost countries, for whom food production is a major issue. About 60% of the cost of microtuber production is labor, which is the largest single contributing factor. Since Switzerland is a relatively high labor cost country (both in terms of direct salary and indirect social benefits) it is clear that the technology could be much more economically instituted in lower labor cost environments such as Asia, Africa and Latin America.