Weed hosts of Xylella fastidiosa in Brazilian plum orchards
Studies on the possible role of weeds in the epidemiology of plum leaf scald disease caused by Xylella fastidiosa (EPPO A2 List) have been conducted in Brazil. Twelve weed species present in five plum (Prunus salicina) orchards heavily affected by plum leaf scald were tested by PCR for the presence of X. fastidiosa. These orchards were located in two plum-growing regions, in Jarinu (São Paulo State) and Videira (Santa Catarina State). Out of the 12 weed species tested, 9 were found to be naturally infected by X. fastidiosa: Bidens pilosa, Lepidium ruderale, Lolium multiflorum, Plantago major, Parthenium hysterophorus, Raphanus sativus, Rumex sp., Solanum americanum and Vernonia sp. The highest infection rates were found in samples of Lepidium ruderale and Lolium multiflorum. In greenhouse experiments, mechanical inoculation of 4 selected weed species (B. pilosa, L. ruderale, R. sativus and S. americanum) with plum-infecting strains (X. fastidiosa subsp. multiplex ST26, ST67 and X. fastidiosa subsp. pauca ST71) induced systemic infections. The authors concluded that these naturally infected weed species can serve as alternative hosts of the bacterium and might play a role in the disease spread in plum orchards. They also noted that further transmission studies involving weeds, plum trees, and insect vectors are needed to better understand the role of these weed species in the disease epidemiology.
Sources
Müller C, Esteves MB, Kleina HT, de Melo Sales T, Boti Liva K, Balbinote J, Spotti Lopes JR (2022) Weeds as alternative hosts of Xylella fastidiosa in Brazilian plum orchards. Journal of Plant Pathology 104, 487–493. https://doi.org/10.1007/s42161-021-00979-y