Role of weed hosts as pathogen reservoirs of insect vectored diseases (WEEDVECT)

‘Candidatus Liberibacter solanacearum’ (Lso) is a phloem-limited phytopathogenic bacterium vectored by psyllids. Lso has caused major damage in Solanaceous and Apiaceous crops worldwide where the psyllid vectors use cultivated crops as their main host or food plant. Psyllids often have a limited range of plant hosts but may feed on plants closely related to their host. The diversity and availability of plant hosts surrounding crops plants can significantly influence the epidemiology of Lso because of vector feeding behaviour and migration (Cooper et al. 2016). In many regions the presence and diversity of Lso and its vectors is poorly understood, especially for weed hosts surrounding cultivated crops. The WeedVect project aimed to develop a better understanding of Lso, in terms of its crop hosts, vectors and native/weed hosts. Knowledge on potential vectors and natural reservoirs of Lso may help to anticipate or prevent outbreaks in new areas and mitigate the impact on crops in existing areas.

Liberibacters have been found in several psyllid species and while some seem to be benign, others are known as the causative agents of plant diseases with significant impacts on crop production worldwide. For Lso several new plant and psyllid vectors are being described and different Lso haplotypes are being characterised. Discovery of these alternative insect vectors and plant hosts will improve our understanding of Lso interactions with plants and insects, evolution, and epidemiology and will inevitably increase knowledge on new haplotypes of Lso, thus broadening current knowledge on the bacterium taxonomy.

WeedVect is a consortium of 3 institutions working to better understand the role of weed plants in the epidemiology of Lso. The consortium has also explored the potential role of aphids and other hemiptera as vectors of Lso. The project aimed:

• To improve the understanding of Lso diversity and presence in weed hosts including findings of Lso in previously unreported non-crop host plants
• To improve the understanding of Lso diversity, including the characterization of new Lso haplotypes, and presence of Lso in psyllids,
• To identify Lso within non-psyllid plant-sucking insects, including the characterization of new Lso haplotypes
• To assess the potential for using DNA barcoding to identify food plants of psyllids and other plant-sucking insects