Science Hybrids More complex More And more complete added value When breeders produced the first varieties by cross-breeding back in the early 20th century, they discovered that they often performed better than the true-to-type cultivars in use at the time. It would be another 50 years before these hybrids gained widespread acceptance in agriculture and horticulture, but since the 1950s they have gone on to become a permanent fixture. 20 | The Partnership In a nutshell, growers of a true-to-type – i.e. open-pollinated (OP) – variety, use seed from the previous harvest for their next production. A hybrid, on the other hand, is a cross between two true-to-type, fixed parent lines. The result is a uniform variety with significant added value. "With a hybrid, 1x2 doesn’t make 2 but 3 or more,” says Wouter Lindeman, Crop Research Manager Pepper. “That comes from the heterosis effect, in which traits in a hybrid are expressed more strongly than in either of the two parent lines. Because a hybrid obtains the genetic properties of both parents, it combines more traits and therefore more genetic variation than an OP variety." This enables breeders to combine resistances in a single hybrid which could not be combined in a true-to-type variety. This not only applies to disease resistance genes but also to a large number of other traits, such as improved resilience to abiotic stress factors e.g. the ability to perform well in both wet and dry climates and on saline soils. Thanks to this environmental resilience, they are better able to cope with climate change. All in one single variety! Complex and labour-intensive Because of the crossing work involved, breeding F1-hybrids is even more complex than the already time-consuming selection process for true-to-type (i.e. open-pollinated) varieties. Lindeman: "First we have to develop uniform parent lines and fix them, in order to produce hybrid seed the following year. These testcrossings are trialled for two years before varieties with added value reach the commercial stage. Producing large quantities of seed for commercial sales requires large numbers of crossings and is therefore very labour-intensive." In our breeding work, to avoid manual emasculation and thus simplifying the crossing procedure, we are increasingly focusing on varieties of which the mother lines don't produce pollen and are therefore male sterile. That saves us having to pollinate manually for seed production because we can leave the pollination to insects. When it comes to seed quality, the choice of mother plant is crucial. After all, the seed of the hybrid is harvested from the mother line, so breeders prefer to select a mother line with the capacity to produce a lot of high-quality seed. Challenges A hybrid variety therefore offers many agronomic advantages, but is complex and presents quite some challenges, both for breeding and seed production. For example, the female and male The Partnership | 21
Loading...
Loading...
Loading...
Enza Zaden Brochures