Identification of the Causal Agent of Downy Mildew of Plasmopara viticola Grapes by Quantitative PCR

A new method is proposed for the early diagnosis of the causal agent of grapes downy mildew, Plasmopara viticola, based on the method of quantitative real-time PCR (qPCR RT) using SYBR Green I fluorescence. Six pairs primers were developed for the diagnosis of P. viticola, among the designed primers, PvITS1_2-real-s/a demonstrated the highest effectiveness for early detection of grapevine downy mildew with a strong positive correlation with the metagenomic data of P. viticola distribution in Far Eastern grape species and varieties, where a linear dependence was found (R2 = 0.86). Thus, qPCR RT of PvITS1_2 can be used for early detection and monitoring of asymptomatic P. viticola infections. The developed method can be used as a basis for predicting epidemics of downy mildew of grapes and for its control in vineyards.