Hybrid Wheat - What's taking so long??
Hybrid Spring Wheat to hit the Northern Plains
Syngenta has announced their intentions to release hybrid spring wheat in our region. The target is somewhere between 5,000 to 7,000 commercial acres for 2023 planting. Bayer, BASF and Corteva are also working on the venture to bring hybrid spring wheat to North American farmers and plan to have hybrid releases available for sale at some point during the next 10 years.
Now most newsletter authors would probably just stop there, but since I have a well-educated audience, the question will inevitably arise, “why has hybrid corn been around since the 1930’s and we are just now getting hybrid wheat - almost a full century later in history?” Well, let’s have a little fun by diving into the challenges of making hybrid wheat and how it’s vastly different than breeding hybrid corn – I promise to try and keep it simple and concise!
Hybrid wheat will differ from conventional wheat with the pollination or kernel fertilization growth stage. In a conventional wheat variety, the plant undergoes a natural self-fertilization process where both males and female reproductive parts are located on the same plant (termed “monoecious” – meaning “one house”). Therefore, if a hybrid (defined as a cross between two genetically different and pure parents) was desired, the process of fertilization must be completely separated. The ability to mass scale the process would also be critical for seeding tens-of-thousands of acres of the progeny under broadacre farm production.
For hybrid corn (maize) development, the process was fairly simple for breeders to execute since that particular monoecious plant had the male pollen expressed though the tassel (at the very top of the plant), and the female was expressed with the silks of the ear in the middle area of the plant – a couple feet physically lower than the tassel. Thus, corn plant breeders materially removed the tassel a couple days before expression from one inbred parent (making those plants female by default) and then letting the pollen of another inbred of different genetics (males) fertilize the intended females. Shortly after the fertilization process, the males were destroyed to insure only seed from the females were harvested. Seed corn producers often plant a row or two of males for every three to six rows of females and allow nature (wind) to move the millions of extremely light weight pollen grains per male plant to fertilize the hundreds of silks/ovules per female plant. This process revolutionized corn plant breeding and hybrid vigor gains led to very quick advances in productivity – the average production per acre was fairly stagnant at around 25-30 bu/ac in the decades leading to and including the 1920’s. Today, corn productivity is approaching 180 bu/ac!
https://farmdocdaily.illinois.edu/2022/07/perspectives-on-national-u-s-corn-yields....
Unfortunately, the male and female parts of a wheat plant are contained in the same flower (only separated physically on the plant by a millimeter or two at most), which makes the process more complex to reach a significant volume of produced hybrid seed. Traditional wheat variety breeders make genetic crosses in the laboratory by using tweezers to remove anthers from females and introduce pollen from desired males to subsequently fertilize the female ovules – a tedious labor-intensive process and after the cross, it takes many generations of seed production to ramp-up significant volumes.
The initial concept of potentially developing hybrid wheat dates back to the 1950’s when plant breeders discovered a procedure to create cytoplasmic male sterility (CMS) germplasm. This procedure basically renders a monoecious plant as female reproducing only (pollen may still be produced but is not viable). With the invention of CMS, came the ability to easily produce a high volume of plants which would accept a different source of genetics through introduced pollen. Basically, the CMS line becomes the female parent, and another variety (non-CMS) becomes the male. If you then harvest only the females, you have basically created a hybrid. However, in this system as described, the harvested progeny (F1) expresses an unpredictable mix of male sterility and male fertility – potential problem of liability for the breeding company selling the F1 hybrid seed to farmer customers. Even with the selection and implementation of “restorer” genes – restores male fertility to the offspring of CMS female lines – the process is not as clean and straightforward as desired, plus it dramatically enhances the complexity of the entire hybrid wheat breeding process. Lastly, wheat pollen is very heavy as 90% of the male pollen will fall at the base of the plant, creating further issues when planning large scale hybrid seed production.
At the end of the day, the cost of producing and maintaining three different genetic lines (CMS female, non-CMS maintainer male, and restorer) to garner large volumes of hybrid wheat seed is very expensive. Additionally, at the end of the breeding cycle, F1 hybrid wheat seed still contains some level of male sterility. Current research reveals today’s plant breeders are finding better restorer genes and working combinations of those restorer genes to increase the chances of profitability for both the breeding team and the farmer customer who ultimately plants and raises the product. It’ll be interesting to see over the next few years if Syngenta can demonstrate consistent hybrid wheat performance, consistent hybrid wheat supply for their customers, and consistent profitability in their business venture.
https://news.agropages.com/News/NewsDetail---45130.htm
https://www.nature.com/articles/s41467-021-21225-0
https://www.biorxiv.org/content/10.1101/2020.06.20.162644v3.full
Comments
Post a Comment