b'BUILDING A MORE RESILIENT CUCUMBERLIKE ANY CROP, CUCUMBER IS THREATENED FROM ALL SIDES, BUT BREEDERS ARE WORKING TO HELP THE FRUIT BETTER SHIELD ITSELF.BY: MARCEL BRUINSEDITORS NOTE:C ucumber is plagued by numerous pests andwith field and plant health organisations in order diseases such as powdery mildew, CVYV,to be prepared for the outbreak of any new dis-If you haventCYSDV, downy mildew (DM) and severalease, he says. read Part 1 of ourothers. Bal says they are indeed breeding forAccording to Kraan, it seems that most cucumber series,resistance to powdery mildew, CVYV and CYSDV.simple inherited resistances are incorporated please stop andFurthermore, we give a high priority to resistancein the breeding programs. The other resist-go back to page 6to CGMMV, downy mildew, gummy stem blight andances are generally polygenic, often with inter-and bring yourselfFusarium. actions between the individual genes, and as a up-to-speed. ThenAust indicates that in the southern parts ofresult incomplete. Incorporating these disease come back here andEurope and in the Czech Republic, ZYMV hasresistances in the breeding programs is quite read on! developed, which is transmitted by vectors, mostlya challenge. CGMMV and CYSDV are globally aphids.important diseases, and for sure new ones will The biggest problems with ZYMV are causedappear in the future.in pumpkins and zucchini. However, smooth typeAbad agrees that in the Mediterranean cucumbers are the most vulnerable. Theyarea, CYSDV and CVYV plus PM are now a must. reduce the growth and yield of fruits, he says.And thus, at Syngenta we are already introduc-That is why ZYMV resistance is importanting the 3D (three diseases full package) in all in addition to classical mould tolerance.the materials. Still, DM is a very important dis-For greenhouse cucumbers, due to theease where the previous resistances introduced intensive growing in the shelters, it isin Europe were not really making a significant necessary to monitor the whole set ofdifference, now we are working on that with the resistance such as powdery mildew,4D package. New diseases are becoming critical, ZYMV, CMV, CCu, CVYV, etc. like CGMMV and TolCNDV.For Gonzlez-Cabezuelo, the basic resistance set of their varie- RESISTANCE LEVELSties is powdery mildew, CVYV,The goal of Aust and his company is to provide andCYSDV.However,varieties with a maximum level of resistance to depending on the varie- all pathogens. Of course, in the overall assess-ties, CMV resistance is ament of the variety and its intended use, we must. On the other hand,can approach the compromise in the form of a weareworkingwithmedium degree of resistance, depending on the other resistances suchimportance of the pathogen in question.as CGMMV, ToLCNDV,Bal indicates that all of their varieties are downy mildew, etc. Wein the Intermediate Resistant (IR) or Highly arealwaysworkingResistant (HR) categories. Most resistances in cucumber are not com-plete, says Suelmann. For example, a powdery mildew resistant variety shows fewer symptoms than a susceptible variety. Still, symptoms will be found when the plants are staying in the greenhouse a long time. That said, the must have resistances are generally on a good level. But several viruses (CGMMV, to name one) are spreading and require a lot of attention to deliver varie-ties with a good resistance level to the market.18IEUROPEAN SEEDIEUROPEAN-SEED.COM'