RE SEARCH New plant breeders’ rights protocol offers scope for potato seed the internal differences between hybrid varieties themselves, and the difference between hybrids and the vegetatively-propagated varieties. The Oliver variety is, therefore, an SIP hybrid. ‘We have concluded that this hybrid is sufficiently stable.’ ‘Naktuinbouw officially doesn’t know anything yet about the HIP hybrids. In 2016, Solynta registered one parent line, but after a year, that line was withdrawn again’. ‘We haven’t seen the HIP hybrid yet.’ Relating uniformity to propagation method The ultimate question is how to assess this hybrid material according to the DUS requirements. ‘Looking at distinctive qualities, the first question is going to be what should we compare it with? This is a Solanum tuberosum, but one that doesn’t compare with current potato varieties. To find something similar, we first looked for similarities in open pollinated crops, but they don’t compare because they are very diverse. Some TPS hybrid material is available at the international potato centre (CIP) in Peru, but we won’t be able to use that in the Netherlands because of different climatic conditions and particularly because of the phytosanitary barriers. This is why the hybrid Bejo variety can be deemed to be distinctive because there’s no material with which you can in any way compare it’, Hof concludes. ‘Article 8 of the UPOV stipulates that we must include the uniformity of a variety. What is meant here is whether the variety is sufficiently uniform in the relevant characteristics. This is why hybrid varieties require a different eye than the current potato varieties. This means that we relate uniformity to the propagation method of the variety’, Hof continues. ‘For vegetatively-propagated potatoes, we look for noncompliant plants in a plot. In a population such as these SIP hybrid and cross-pollinators such as ryegrass, all plants are slightly different, and you can’t speak of non-compliant ones. We then examine whether the variation in a variety is not too great and whether the variety is uniform in time. It was difficult to determine whether we found this hybrid potato variety sufficiently uniform because we didn’t have any material of registered varieties to compare it with. The plant breeders’ rights for the Zolushka variety, also originating from Bejo, which was applied for in 2002, wasn’t yet sufficiently uniform. One of the conditions is that a variety has its own identity, which you should be able to describe. For hybrids of this type, you must accept a certain degree of variation. How much variation is acceptable has now been established in the plant breeders’ rights under which the Oliver variety falls. To establish this, we were able to use a lot of knowledge and experience from our Naktuinbouw colleagues who work with other crops. They were able to help us assess what was and what was not sufficiently uniform. For TPS, we chose to describe thirty individual plants at least twice and assess the yield from one trial field with first-generation tubers grown from seed. With this field of tubers, we are better able to assess the maturity of the variety, because we do this on the basis of comparing it to the earliness of vegetatively-propagated potato varieties. The reason is that it’s difficult to compare the maturity of plants bred from seed with plants bred from a tuber’, Schipper explains. ’For next generations of hybrid varieties of this type, we now have a minimum reference that varieties should meet in order to be uniform. The UPOV rules have a formula of the relative variance method, which also applies to other crops. ‘When a potato breeder looks at a field with the TPS Oliver variety, he or she will come to the conclusion that there is more variation than usual’, Jan Kees Schipper comes to the point. 14 Potato World 2017 • number 3 Pagina 13

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