Although hybrid varieties are theoretically nothing new, as the phenomenon of heterosis responsible for their creation was described exactly 110 years ago, the first hybrid varieties of corn appeared on the market "in the West" in the 1950s, and the history of Polish hybrid rye varieties dates back to 1994, many farmers still do not know what "hybrids" are all about. Reaching a bit for scientific issues of plant breeding, but at the same time translating them "from Polish to ours", we will try to explain how hybrid varieties are created and why they are sown only once.
The History of Hybrid Varieties, or a Hundred Years Ago in America
The first observations of the exceptional luxuriance of certain hybrids, without yet understanding the phenomenon, were described in 1761 by the German botanist Joseph Kölreuter. Heterosis was defined as such by the American botanist, George Shull, who came from a farming family, in 1914. He conducted research involving the crossing of inbred corn lines, i.e. those forced to self-pollinate, obtaining even twice as much yield.
Read more
Strip-till: the ideal crop for rapeseed?
In the 1950s, the first hybrid varieties of corn began to appear on the market in Western Europe, which contributed to a spectacular increase in yields. Interestingly, this technology reached Poland not much later, and although corn did not gain greater popularity until several decades later, the first hybrid varieties were already available in the 1960s.
In the case of rapeseed, the history of research on hybrid varieties dates back to the 1970s in Western Europe, and the first of them were registered in the last years of the 20th century. In the case of cereals, the importance of "hybrids" is slightly less, but the first Polish hybrid rye variety was registered in 1994, i.e. 30 years ago. In the studies at that time, it produced a yield higher by up to 25 percent than other varieties available on the market.
Advantages of hybrid varieties
Hybrid varieties stand out from traditional populations by using the heterosis effect, i.e. the growth of hybrids. This causes the advantageous features of the parent lines to be highlighted, with a high grain or seed yield resulting from, for example, a higher grain density or a higher thousand-grain weight. Depending on the species and the specific variety, the positive difference can reach even several dozen percent.
Read more
Which variety of winter rapeseed to choose? LOZ recommendation for Integrated Production
But that's not all. Many hybrid varieties have a more developed root system, which makes better use of water and nutrients. In addition, they are characterized by better vigour and faster development, and in the case of winter plants, also better winter hardiness. In the case of cereals, stronger tillering is also observed. However, the high price of certified seed material and the lack of possibility of sowing material from your own propagation remain a certain disadvantage. However, comparing the balance of profits and "losses", a hybrid variety is often a good investment.
Breeding of hybrid varieties
As we have established above, breeding hybrid varieties involves crossing inbred lines, which are therefore forced to self-pollinate. Like any other breeding of new varieties, it is a difficult and lengthy process, and the desire to obtain a hybrid with the desired characteristics revealed in the F1 generation makes it even longer and more difficult. A lot of work and specialist knowledge is required both to create inbred lines and to cross them appropriately. Inbred lines of today's hybrid varieties are subjected to self-pollination many times to be 100% certain about what gene pool they have.
Read more
How much should you pay for rapeseed seed purchased at the last minute?
Then, male sterile forms and pollinators are sown, thanks to which the aforementioned effect of heterosis is observed in the F1 generation, i.e. the ecstasy of hybrids. This can be written in the form of a genetic cross (ACMS x B) x RSYN. Then (ACMS x B) is the maternal side, which is a simple hybrid, i.e. a cross between inbred line A with CMS cytoplasm, which prevents pollen production, and inbred line B with normal cytoplasm. RSYN is of course the paternal side, called the restorer, consisting of two population lines, the task of which is to restore male fertility.
The hybrid is sown only once
Thanks to the complicated crossbreeding described above, the effect of heterosis, i.e. the exuberance of the hybrid, is observed in the F1 generation. If the grains or seeds obtained in this way were sown again, this effect would no longer be observed, due to uncontrolled crossbreeding and the dilution of desired features. Hybrid varieties are genetically created to emphasize their advantages only once.
Read more
Farmall from 1946 from new in Poland
In the F2 generation, we are already observing genetic variability rather than trait inheritance to a large extent. Yes, no one will forbid sowing, but we will not see the effect and it will not be the fault of, as some call it, a "weak variety". This is the specificity of "hybrids". The decrease in yield in the F2 generation is estimated at an average of 30-40%, depending on the species and variety. However, this is not all, because variability also occurs in genes that determine other traits, which is why we can observe, for example, disorders in the growth, development or shape of plants.
