Set up of a bioassay for evaluating Beet Mild Yellowing Virus resistance of sugar beet cultivars

Abstract

The Beet Moderate Yellows Virus (BMYV) has been effectively controlled in recent years in the European Union through the use of chemicals as a means of controlling its vectors, neonicotinoids. However, this protection via neonicotinoids is now over following the abolition of their use in the European Union since 2017. Chemical alternatives exist but the emergence of resistance in aphid populations requires the development of new control methods. This is why the development of resistant or tolerant cultivars has been implemented by seed companies such as SES VanderHave. To do this, a bioassay was conducted to assess the presence or absence of resistance for a given cultivar. To develop this bioassay, a potentially resistant and susceptible variety was first inoculated by five virus-infected aphids of the species Myzus persicae, which is the main vector of this viral disease. This inoculation was performed by Clip-cage on all plants in the bioassay and the aphids were left four days to allow transmission of the virus. Three types of leaves were then collected from each plant every week during three weeks. The quantification of the virus was carried out by using a semi-quantitative ELISA, allowing the analysis of the relative virus concentrations in the different leaves for the two varieties. The two varieties showed significant differences between them and the potential for quantitative resistance was observed for the resistant variety. In addition, measuring the viral concentration two weeks after inoculation seemed to be sufficient for optimal virus detection. Indeed, the viral concentration was significantly higher during the second and third samples compared to the first. It would be interesting to repeat this quantification to confirm the results obtained. Finally, a real-time RT-PCR for faster and more sensitive detection was developed and the preliminary results are presented.