Technology | Summer 2008
The making of a canola hybrid.
By Kieran Brett
Every new canola hybrid is the product of a complex and expensive breeding process. The payoff: improved productivity that's driving open-pollinated varieties into the history books.
Amazing things happen when you plant hybrid canola seed. Because today's hybrids are far more vigorous than old-style open-pollinated canola, the young plants emerge more quickly and in better shape.
Even when conditions are less than perfect, the plants' hybrid vigor makes the best of it. Come harvest, your hybrid canola will yield more than any open-pollinated variety. In fact, over the past decade, the performance of hybrids has made open-pollinated canola an increasingly rare sight in Western Canada.
What is a hybrid?
A hybrid is a cross between two genetically different inbred parent (male and female) lines. Half the resulting hybrid's genetic make-up is supplied by the female parent and half by the male. That's where the hybrid vigor comes from. The benefits of hybridization include more robust plants, better agronomic characteristics, and higher yield.
Because canola is normally self-pollinating, its male and female parts are on the same flower. So creating a cross-pollinated hybrid is more complicated than with corn where male and female organs are physically separated. Canola breeders need to prevent the female parent line from making pollen so it doesn't fertilize itself. Creating this so-called male sterility trait is tricky and can be done in different ways.
Inside two systems: Bayer and Pioneer
The process used for Bayer CropScience's InVigor hybrids started at the University of Ghent in Belgium in 1989. There, researchers found ways to stop pollen from being produced on the female (male sterile) plant. The only source of pollen would then be from the male plant selected by the plant breeder to make the hybrid.
Bayer's proprietary system creates a female plant that does not produce pollen, and a male plant that does produce pollen and restores fertility. When crossed, the two produce a hybrid.
This system allows development of parental lines in all genetic backgrounds, enabling plant breeders to develop superior hybrids for commercial canola growers. This flexible system provides InVigor breeders with virtually unlimited combinations of genetic material. Parental lines can thus be farther apart genetically, which increases the level of hybrid vigor in the offspring seed.
"Much of the success of the InVigor system lies in the fact that it is very environmentally and genetically stable," says Stewart Brandt, Bayer CropScience plant breeder and manager of breeder operations in Saskatoon. "This means we can produce our hybrids in virtually any background, which allows us to make any hybrid cross we want."
Dave Charne, research director with Pioneer Hi-Bred, explains that Pioneer's hybridization platform is known as OGU-INRA, a French-Japanese system adapted by Pioneer to make it suitable for canola. This system is also based on achieving male sterility, but the technology is different.
Pioneer's Cytoplasmic Male Sterility (CMS) method of hybridization controls fertility at the cellular level. Through CMS, breeders can produce female plants that either don't produce pollen, don't release pollen or whose pollen won't result in self-fertilization. The use of different lines allows breeders to switch fertility off while hybridization is taking place, then switch it back on for field production.
Charne says a key issue in hybrid canola seed production is that even the smallest quantity of pollen at the wrong time is enough to create undesirable self-pollination. As hard as plant breeders work to achieve hybridization, the canola plant's physiology is pulling in the opposite direction.
An individual canola flower, he explains, develops a pod with 30 to 40 seeds. The same flower has six anthers, which can produce something on the order of 20,000 pollen grains. With the canola plant going all-out to self-pollinate, achieving 99 per cent sterility isn't good enough.
"The challenge with hybrids is that you have to shut down pollen production completely," he says. "If 20,000 pollen grains come from a flower, and there's even 1 per cent pollen leakage, that's 200 grains of pollen."
Hybrid seed production
Just as hybrid plant breeding is more complex than open-pollinated, hybrid seed production is likewise significantly more demanding.
InVigor seed is grown by seeding alternating bays of the male and female lines. Male plants produce pollen and are tolerant to the herbicide Liberty. Female plants contain the male sterility gene, which also is linked to the Liberty tolerance gene. So, Liberty can be applied to the entire crop to keep it weed-free. Application of Liberty also completely prevents the female from producing pollen. If the female plants did not have the male sterility gene, they would also not have the gene for Liberty tolerance and would be controlled by the herbicide application. This extra level of genetic assurance helps achieve an exceptional level of hybridity.
Lionel Lamont, Bayer's manager of canola business operations for North America, explains that producing InVigor seed is a three-step process. The first step, called pre-basic seed production, happens in isolated cages or tents. Each plant is individually tested as it grows to ensure that it has the correct genetic profile.
The second step, called basic seed production, is a highly controlled production process using isolated small-field plots to ensure the plants' superior genetic profile continues in the field. Field-scale Certified seed production is the third step. Here, Bayer agronomists work closely with seed growers to achieve purity.
"We grow the pre-basic in pollination control cages or tents, the basic in British Columbia, and the commercial Certified seed in the Lethbridge region," explains Lamont. "These areas provide relative isolation from foreign canola pollen, which reduces the risk of outside pollination. They also have access to irrigation and a slightly longer growing season."
From initial genetic screening to the intricacies of plant breeding and the exacting standards of seed production, hybrid canola is the work of hundreds of skilled and dedicated people. Their efforts are rewarded when commercial growers pay premiums for the seed to improve their chances of harvesting high-yielding, high-margin crops.
