What Does It Take to Make a Hybrid?
An in-depth look at hybrid seed production
With more than 65% of total Canadian canola acres being planted to hybrids in 2007, canola growers have clearly recognized the tremendous yield potential hybrids offer.
So what goes into making a canola hybrid?
A hybrid is the first generation of seed produced from a cross between two or more genetically unique inbred parent lines. The combination of genes from the two parents results in a hybrid plant that exhibits all of the most desirable characteristics of the two parents – and – performs better than either.
The goal of the breeder is to find high-performing parents with certain attributes so that when crossed, their offspring is a superior high-performing hybrid that produces a profitable crop for farmers and oil with the desirable fatty acid profiles and stability that end-users demand.
Corn was the first agricultural field crop to be successfully hybridized. But compared to canola, the process was simple. Male and female parts on corn are physically separate. In canola, male and female parts are in the same flower so breeders couldn’t rely on physical separation to achieve the 100 per cent cross needed to produce hybrid seed.
For approximately 30 years, canola research focused on a genetic mechanism to inhibit self-pollination. By the early 1990s, after evaluating many different systems, most were discarded, leaving only two reliable processes to further refine. One, the OGU INRA system, is based on cytoplasmic male sterility. The other one is a molecular based process developed by Bayer CropScience.
To make hybridization work in canola, two components have to be developed. First, you need to make the female inbred male sterile. That means, the female line produces no pollen but can be pollinated by another line. Relating that to corn, it’s like removing the tassel but still having the silk. The second step is to restore fertility in the seed produced from the cross so that when farmers plant the F1 hybrid seed, the crop can flower and self-pollinate. Breeders accomplish that with a fertility restorer gene that is present in the male inbred to be used in crossing.
The restorer gene is completely dominant so all of the seed resulting from the cross grows flowers and looks just like a conventional open-pollinated canola crop. However, if growers try to replant the seed from a commercial field, the restorer gene would segregate and a portion of that seed would be male sterile. The F2 seed would also have segregated all other traits and uniformity would be lost.
Once the science to hybridize canola had been secured, successful commercialization depended on continuous and significant yield advantages over traditional open-pollinated varieties. And that depended on a germplasm base to provide the potential to develop heterosis or hybrid vigour. Simply expressed, hybrid vigour is the performance advantage exhibited by the hybrid over its inbred parents. Heterosis isn’t achieved for all traits, but it is for yield.
But yield isn’t the only thing farmers are looking for in hybrid canola. They also want disease resistance, herbicide tolerance, appropriate maturity, low green seed content, lodging tolerance, and acceptable oil and meal quality. The breeder’s challenge today is to develop a well-structured program that allows them to make, screen and classify inbreds. From there, they need to test for heterosis and identify combinations that give the best performance. Candidate hybrids need to be screened and evaluated in the environments they will ultimately be commercialized in.
It’s a given that a good hybrid will have all the traits that open-pollinated varieties contain. The plus is canola hybrids offer significantly higher yield. How much higher? Often as much as 9 to 21 per cent over open-pollinated varieties.
Hybrids provide growers with significant yield increases and today they cover over two-thirds of all Canadian canola production. That’s up from only 27 per cent in 2002 1. The transition to hybrids will continue because hybridization can achieve more rapid and steady improvements in both yield and other critical traits.
And InVigor canola hybrids are leading the way. An outstanding canola breeding program is built on a foundation of exceptional germplasm and highly reliable seed production. InVigor hybrids are created through the unique molecular pollination control system. Other systems can produce only a limited number of females.
This unique system provides InVigor breeders virtually unlimited access to germplasm and a superior way to maintain sterility. That means InVigor hybrid parents can be further apart genetically, increasing the level of heterosis or hybrid vigor the F1 offspring express. The SeedLink system also allows Bayer CropScience to install the male sterility gene and a gene for resistance to Liberty herbicide in the female simultaneously.
The InVigor seed production system is also unique. Production takes place by seeding alternating rows of males and females. Only the male plants produce pollen. And the male sterility gene is linked to the Liberty gene. That means that during production, the field can be sprayed with Liberty, keeping the field weed free and completely prevents females from producing off types. As such, InVigor hybrids maintain an exceptional level of genetic purity.
InVigor seed production is broken into three steps:
- Pre-basic seed production
- Basic seed production
- Certified seed production
STEP 1: Pre-Basic Seed Production:
To maintain genetic purity, Pre-Basic seed production is performed in the interior of British Columbia where no commercial canola is grown that could contaminate InVigor seed. In the off-season, contra seed production takes place in an isolated region of Australia – again where no commercial canola is grown.
The production of both males and females is done in tented facilities where each plant is tested for superior genetic profiles.
STEP 2: Basic:
The next generation of seed production – called Basic Seed – is still done in the B.C. interior and in Australia. These highly controlled small field plots produce females under tents to ensure the superior genetic profiles identified a generation ago continue.
STEP 3:
Certified Seed Production: The final stage of seed production is performed by professional commercial seed growers under agreement with Bayer CropScience. Most of these growers are located in Southern Alberta.
Certified seed growers seed alternating bays of male and female plants. Only the males are allowed to produce pollen and only the females produce seed. This means only a portion of each field is harvested for commercial certified seed.
Bayer CropScience is ruthless in their selection process. Our extensive in field screening trials keep breeders searching for only the best. Our world-class breeding program secures the leadership position for InVigor hybrids well into the future. Every year, our unforgiving performance standards force us to reject more hybrids than the competition submits for registration.