Grapevine yellows in Jordan: Associated phytoplasmas, putative insect vectors and reservoir plants

Field surveys were conducted in wine and table grape vineyards from June to October 2020 in 13 locations belonging to five governorates in North and South Jordan. Typical grapevine yellows symptoms, including leaf reddening/yellowing and rolling were observed on 10% to 55% of vines. Nested PCR-based amplification of the 16S rRNA gene detected phytoplasmas in 22% and 15.7% of the analysed symptomatic wine and table grape cultivar plants, respectively. Amplicon nucleotide sequence analyses identified the detected phytoplasmas as Candidatus Phytoplasma solani (taxonomic subgroup 16SrXII-A), Ca. P. omanense (16SrXXIX-A and -B), Ca. P. aurantifolia (16SrII-C) and Ca. P. asteris (16SrI-R) in 72.4%, 17.2%, 6.9% and 3.4% of infected plants, respectively. Such phytoplasmas were found differentially distributed in wine and table grape cultivar vineyards surveyed. Further investigation identified Ca. P. solani in the putative insect vectors Orosius cellulosus (first report in Jordan), Euscelidius mundus, Laodelphax striatellus, and Circulifer sp., and in bindweed; Ca. P. aurantifolia in the insect O. cellulosus and in bindweed; Ca. P. omanense in the insect Psammotettix striatus; and Ca. P. asteris in the insects Arboridia adanae, Cicadulina bipunctata, Circulifer sp., L. striatellus, Hyalesthes obsoletus, and P. striatus. Based on this preliminary data, ecological cycles of such phytoplasmas are discussed. Results suggest that the diversity and ecology of grapevine yellows phytoplasmas in Jordan are more complex than previously known, leading to a potential risk of disease outbreaks.

Automated summary

Field surveys conducted in Jordan found that grapevine yellows phytoplasmas, including Candidatus Phytoplasma solani, Ca. P. omanense, Ca. P. aurantifolia, and Ca. P. asteris, were detected in both wine and table grape vineyards. The phytoplasmas had differential distribution in the surveyed vineyards. Insect vectors and bindweed were identified as potential sources of the phytoplasmas. These results indicate a more complex diversity and ecology of grapevine yellows phytoplasmas in Jordan than previously known, posing a potential risk of disease outbreaks.