Most potatoes grown in the West are clones established from certified seed potatoes. However, for farmers in warmer climes this is not always an option and they face using poor-quality seed, often carrying disease.
Starting with healthy, disease-free seed potatoes is essential for avoiding seed-borne disease that can devastate crops. But in some parts of the world, certified stock is only available through importing from overseas.
Tubers are bulky and perishable, which means the transport costs of importing and delivering certified seed potatoes to farms are considerable, making them unaffordable or unavailable.
Growers are therefore forced to use potatoes they have grown themselves. Typically, the best potatoes are sold, leaving the poorer-quality tubers as seed.
For these farmers, true seed may be the solution being disease-free and cheaper to transport.
One Dutch breeder, Bejo Zaden, is looking to sell into this market, after becoming the first company to gain plant breeder’s rights in the Netherlands. This was for the variety Oliver F1, a hybrid potato that can be grown directly from seed to produce potatoes for the table in just one season.
It is the result of 15 years of development, as the company has worked to reduce variability.
Cultivated potatoes are tetraploid, which means they have 4 copies of DNA and this results in the offspring inheriting a greater diversity of genes. In contrast, seed potatoes are clones – identical to the parent plant.
Potatoes grown from true seed are, therefore, not uniform enough to meet strict European or US specifications. But they are uniform enough to be sold on the African, south-east Asian and central American markets.
Bejo tested Oliver F1 with growers in the Netherlands, with the young plants being first cultivated in the greenhouse, before being planted out in fields.
The plant needs time to become established, explains Bejo Zaden crop manager Rien van Bruchem, which takes 5 to 10 days.
Once the plant has become established, things start to move quickly, as the company says true seed potatoes are fast-growing.
“The yield is lower than what we are used to in the Netherlands, averaging at about 45-55t/ha.”
Bejo is continuing to develop true potato seed, including other varieties, and is currently investigating whether it can speed up germination using priming (pre-germination of seed).
“We are also testing prilled seed in order to make the fine potato seed suitable for use in conventional seeders already on farms,” says Mr Van Bruchem.
As mentioned before, potatoes produced from true seed are not suited to European markets.
In addition, the climate in Europe is too cold. “In our climate, potato seed is barely capable of germinating outdoors, as the soil temperature is too low.
“For that reason, you need to sow the seed in a greenhouse and then move the plants outdoors once they start to germinate.”
This makes it too expensive in Europe because of the large amount of manual labour involved.
While the company does not see true seed potatoes replacing seed tubers in Europe, it may affect seed potato exports.
“In due course, true seed potatoes will become a factor in Africa and Asia and that, in turn, may have an effect on exports of seed potatoes to those continents.” However, Mr Van Bruchem adds that is still a long way off.
Bejo is a breeder of vegetable seed and Oliver F1 is the first potato variety to have come out of its breeding programme.
When developing Oliver F1, Bejo used the same approach it uses for other types of vegetable seed, which involves creating homozygotic parent lines.
These homozygotic lines are produced through inbreeding and display a high degree of genetic uniformity. And by crossing these with one another, uniform hybrid (F1) seeds are created that outperform their parents, thanks to the heterosis effect.
After decades of breeding, Bejo has successfully developed a tetraploid potato.
Mr Van Bruchem explains: “True potato seed was developed using a method that is closely related to the way in which tomatoes are bred.
“Breeding using true seed proceeds at a much faster pace than when breeding using seed potatoes.”
The benefit is that when Bejo identifies a successful cross variety, it can proceed quickly to seed production.
In the case of cloned varieties of potato, they need to be propagated for a number of years before commercial seed potatoes can be tested and introduced to the market.
Potato growers need good-quality stock to achieve high-yielding crops and this is more difficult to achieve with seed potatoes than when using true seed.
However, true seed is more variable, creating uniformity issues that would not meet specifications in European markets. Here are the pros and cons of using true seed.