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PALADAPT workshop

Gepubliceerd op
5 april 2019

From 18 to 20 March 2019, the partners involved in the PalAdapt project have organized a workshop entitled “in vitro and miniaturized cyst nematode resistance assays on potato: current use and future prospects”. This workshop was attended by 19 participants, including PalAdapt stakeholders affiliated to either potato breeding companies, NPPO, national safety organizations or reference laboratories for nematode resistance testing in potato.

The first afternoon of the workshop was devoted to presentations. S. Kiewnick (JKI) presented the current methods for PCN resistance assays including the use of potato plantlets derived from sterile tissue cultures using loess soil as substrate (a loosely compacted yellowish-grey deposit of wind‐blown sediment) in miniaturized tests. He emphasized that whatever was the method used the resistance rating of the tested potato cv remains the same. A. Goverse (WUR) presented the tools used for the study of plant resistance mechanisms to nematode infection and emphasized that only a subset of the potato NBS LRR sequences were investigated to date and that basal immunity and susceptible genes could also represent other resources for host resistance. S. Fournet and J. Montarry (INRA) presented the phenotypic and genomic modifications associated with the adaptation of G. pallida to potato resistance. They emphasized the importance of the potato genetic background in the speed of adaptation and expected cross-virulence and warned the audience about some possible fitness advantage linked to the adaptation. Finally, A. Hermann (LfL) presented how the 15.000 tests for resistance to PCN are conducted annually in Bavaria, the equipment and constraints he has to deal with to achieve this work.

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The second day was mostly a practical session that took place in a well-equipped laboratory of the Orion building in Wageningen University. The goals of this session were (i) to learn and improve practical skills (methods and materials to use, do’s and don’ts), (ii) to know more about the parameters of in vitro and miniaturized resistance tests, (iii) to know more about PCN resistance phenotypes in potato (observation of the susceptible response and the rapid or delayed resistance response), (iv) to exchange expertise and knowhow about the different applications and methods.

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The participants have had the opportunity to practice some aspects of in vitro culture like the preparation of in vitro plants by stem cuttings, the preparation of sterile nematodes and their purification and collection using a sucrose gradient.

The workshop has led to fruitful exchanges  and have contributed to the building of a larger network of researchers and stakeholders concerned by the emergence of resistance breaking G. pallida populations and the development of novel control means and potato varieties. Several in vitro or miniaturized methods were presented during this workshop, of which each has its own advantage or limitations depending on the question addressed (i.e. identification of pathotypes, screening for resistance in breeding programs, studying of resistance mechanisms). Another main conclusion of  this workshop was that  the size of the assay, the time constraints and in some cases the need of additional lab equipment and expertise remain major features that will influence the final choice of one test among the others. Overall, the different methodologies presented already allow the addressing of a large  panel of situations and questions, but a lack was identified regarding the use of a miniaturized assay based on potato seeds instead of tubers or cuttings. This is explained by the standard clonal propagation of potato, but this may change in the future considering the developments in hybrid  potato breeding.

The workshop has also highlighted some areas that will deserve  more attention in the near future:

--‐ We are lacking an updated list of reference populations to include in our future assays

--‐ In order to improve  the confidence in the resistance scoring across Europe, instructions should be given regarding the rearing and control of the reference populations

--‐ There is probably also much improvement to gain through digital analysis or machine learning processes for (high--‐throughput) counting or measuring nematodes infections