White-berried grapevines as hosts for polyphagous aphids: analysis of probing behavior, plant leaf anatomy and allelochemicals

Aphids (Hemiptera: Aphididae) are herbivorous insects which deprive plants of nutrients by feeding on the phloem sap and transmission of plant viruses. In the present study, the susceptibility of selected white-berried grapevine (Vitis spp.) cultivars “Aurora”, “Bianca”, “Muskat Letni” and “Solaris” to the black bean aphid (Aphis fabae Scop.) and the green peach aphid (Myzus persicae (Sulz.) was evaluated using the Electrical Penetration Graph (EPG) technique. The content of major flavonoids and stilbenoids in grapevine leaves and leaf anatomy parameters that might have affected aphid probing were also analyzed. Based on the success rate in reaching the phloem vessels and feeding on phloem sap, the studied grapevine cultivars can be assigned to various groups of susceptibility. Cultivars “Bianca” and “Muskalt Letni” are susceptible to A. fabae and M. persicae, respectively (aphids reach phloem phase and show short bouts of sap ingestion); “Muskat Letni” shows low susceptibility to A. fabae, while “Aurora” and “Bianca” to M. persicae (only 50% aphids reach phloem phase and no sap ingestion occurs); “Solaris” is resistant to A. fabae and M. persicae (no phloem phase present). Anatomical structure of leaves was similar in all cultivars and no mechanical barriers for aphid probing were observed. However, the content of individual flavonoids and silbenoids differed among cultivars. We hypothesize that the high content of piceid in the leaves of “Solaris” may be responsible for the rejection of this cultivar by both aphid species. The study demonstrated that the risk of the direct damage due to A. fabae and M. persicae feeding on grapevines is low. However, considering the intense aphid probing activity within leaf epidermis and mesophyll, A. fabae and M. persicae may pose a serious threat as vectors of non-persistent and semi-persistent viruses to white-berried grapevines.