
The doubled haploid method is far faster than conventional breeding.
Doubled haploid method
Doubly stable and genetically homozygous
Our doubled haploid method gives us an enormous breeding advantage and ensures the fixation of useful plant traits. What is behind the method and how do we use it at KWS?
As is so often the case in science, it all began by pure chance: In India in the middle of the 20th century, a scientist was examining tobacco pollen for cell division under the microscope. Afterwards, so the anecdote goes, she forgot to dispose of the slides. After returning to the laboratory, she saw that something had developed on the slides. After several experiments, it was discovered that immature haploid pollen grains divide when placed in a sugar solution – and that was the beginning of the doubled haploid (DH) technology.
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What does “doubled haploid” mean?
During reproduction, both parents each pass on a haploid (single) set of chromosomes. Chromosomes consist of DNA strands and contain genetic information, such as fungal resistance. A haploid set of chromosomes in oilseed rape consists of 19 chromosomes; fertilization creates a diploid set of 38 chromosomes, one from the father and one from the mother.
In the doubled haploid method, the existing single set of chromosomes is duplicated. Doubled haploid, homozygous plants with two identical sets of chromosomes are created from these cells. They retain the genetic information and thus the desired traits.
What does that mean for us in plant breeding? In the best-case scenario, we want to preserve useful traits of a plant such as high yield or particularly good disease resistance in the next generation. In normal crossing, however, the progeny are heterozygous because they each receive one set of chromosomes from the mother and one from the father – meaning the desired traits are lost.
In order to fix a genetic trait, we need to produce homozygous plants, where the chromosome sets are identical, thereby ensuring that the trait is retained. This can be accomplished by traditional means by repeatedly propagating self-pollinating plants with themselves. The progeny are then homozygous after several generations, but it is a process that takes a huge amount of time.
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Doubled haploid production locations
Inception in the 1980s
The doubled haploid method is much faster in the laboratory. “At KWS, we started with the first protocols for oilseed rape and barley at the end of the 1980s and then launched the production programs in the nineties,” recalls Clemens Springmann, head of the Cell Biology research department in Einbeck. He has worked on doubled haploids since 1995, and now does so not only for oilseed rape and barley, but also for sugarbeet as well as cucumbers and peppers for our new vegetable division. “The method gives us enormous advantages because we can develop varieties much faster,” he explains. Two units work hand in hand: Clemens and his team develop the protocols for various crops and determine exactly how the technology is to be applied. The methods developed are implemented in the teams tasked with routine DH production. These are the units headed by Henriett Elek in Einbeck and David Downey in Wageningen. |
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