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VARIETIES
Towards a better protection of new Agaricus varieties
Breeding new varieties of Agaricus bisporus forms a large investment. Bree- ders would like to invest more in new strains, but only if their products are well protected. A working group of spawn producers and researchers has recently been formed to accomplish this.
By Anton Sonnenberg, WUR
New varieties can have a large impact on the mushroom industry. Good examples are the Horst varieties generated many years ago and the recent release of new brown varieties Heirloom and Brawn. There is a demand for new varieties with resistance to diseases and a higher efficiency in substrate utilisation but also for strains with characteristics that are impor- tant for consumers such as a better taste and nutritional
The first button mushroom hybrids
The introduction of the first hybrids (Horst U1 and U3) had a large impact on the button mushroom industry worldwide. The improvement of quality for both fresh market and canning industry and its good yields resulted in a market share of circa 80% within 3 years. The first hybrids were generated by crossbreeding a white and an off-white commercial varieties. It took Dr Gerda Fritsche at that time at the former Mushroom Experimental Station in Horst approximately seven years to generate these new hybrids. Horst U1 and U3 were the first button mushroom varieties that obtained protection by Dutch national Plant Variety Protection in 1980. Within one or two years after their release, however, “new” hybrids appeared in the market that could not be discriminated from Horst U1 and U3. Although it was commonly assumed that these were copies, infringement could not be proven because of a lack of sufficiently distinguishing morphological characters. The use of molecular markers at that time was uncommon. Next to this a specialised court for plant variety protection was lacking at that time. In the following years additional varieties appeared in the market that were similar but, nevertheless, different from the Horst strains. Soon, all spawn producers had their own hybrids un- der different names. The new characteristics of these strains were sometimes an improvement (less scaling, less sensitive to compost quality changes, etc.) and did serve in this way the needs of the mushroom industry. Genotyping of these strains by different sources reported, however, that no or hardly any genetic difference could be found between these strains and the Horst varieties. This indicates that the hybrids were directly derived from the Horst varieties. The breeder’s right on the Horst varieties has expired in the me- antime and to our knowledge no white button mushroom varieties have CPV Rights at this moment.
The contact for the working group is: Anton S.M. Sonnenberg. Plant Breeding, Wageningen UR Droevendaalsesteeg 1, 6708PB, Wageningen, the Netherlands. Email:
anton.sonnenberg@
wur.nl; tel. +31317481336
values. Breeding new strains is a large investment. Breeders are willing to invest in new varieties but only if there is a good protection of new varieties. The European Union law system allows the protection of mushroom varieties by Community Plant Variety Rights (CPVRights), and several titles of protection have already been granted for mushroom strains. In this sys- tem, copies are clearly defined as infringements of the Intellectual property of the holder of the rights. Howe- ver, the generation of derived varieties may still ham- per the investment in breeding of button mushroom, and an agreement of the mushroom industry on how to deal with this subject is desired.
Derived varieties Before the seventies of the last century, spawn pro- ducers and researchers knew that most single spore cultures of button mushrooms produce fruiting bodies. This is unlike most other mushroom species where single spore cultures of different strains must be mated first before fruiting is possible. It was, therefore, long assumed that the button mushroom Agaricus bisporus did not have a sexual life cycle. Strain improvement was done only empirically by mixing spawn or generating multi-spore cultures. Later research showed that also the button mushroom produces spores that do not fruit, although at a low frequency. This type of spores was used to create the varieties Horst U1 and U3. As mentioned, the majority of the single spore cultures of the button mushroom cannot mate, but do produce mushrooms, of which the characteristics are very simi- lar to the mushroom from which the spores are derived. Research has revealed in detail now how the genetic make-up of a strain is inherited by these so called fertile single spores. The fertile spores arise from a kind of self mating. Such spores produce mushrooms that are very similar to the mushroom that produced these spores. Fertile single spore cultures can thus be used to make small changes in a variety and this can be done in an easy way and relatively short time. Recent research has now underpinned that the vast majority of the present-day hybrids were generated in this way directly or indirectly from the Horst U1 varieties.
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