The bacterium Xylella fastidiosa causes the death of over 350 different plant species, standing out the grapevine, almond and olive trees among them.
Using a molecular technique applied to the gastric content of arthropods, a research team from the Faculty of Biological Sciences of the Complutense University of Madrid (UCM) and The National Institute of Agricultural and Food Research and Technology (INIA) is able to detect potential predators of the insect vector that transmits the bacterium Xylella fastidiosa, responsible for the death of more than 350 plant species, including the olive tree, grapevine or almond tree.
This bacterium is transmitted from infected to healthy plants by phytophagous vectors of the Aphrophoridae insect family. The species Philaenus spumarius has been confirmed to be a vector in the European Union.
The treatment with chemical products is the main way to control the insect populations so far. However, these substances have undesirable effects for the beneficial fauna of the olive grove, the environment and even human health.
"Biological control mediated by potential predators present in agro-ecosystems constitutes one of the options that could reduce the use of these chemical products. Thus, the first step is to determine its natural enemies, which arthropods feed on the vector of Xylella fastidiosa", explains Beatriz Matallanas, researcher at the Department of Genetics, Physiology and Microbiology at UCM.
The research, published in Sustainability, addresses the problem of the specific detection of P. spumarius DNA in the digestive tract of other arthropods. In this way the potential predators of P. spumarius can be reliably identified, something practically impossible to determine simply observing the gut content, given the tiny size of prey remains.
By the polymerase chain reaction (PCR) it is possible to detect minute amounts of the vector's DNA. "This technique is reliable even in situations where we expect the DNA to be very degraded, like this one, due to the digestive process," adds Carmen Callejas.
EVEN IMMATURE STAGES
The results showed that 6.34% of the spiders had fed on P. spumarius, a sample "something remarkable considering the low abundance of adult specimens of this vector, given the particular climatic conditions of 2018 spring in Central Spain".
The advantages of the developed method include reliability and speed, which are essential for prompt management actions in quarantine zones. Traditionally, the identification of the vector P. spumarius relied on morphological characteristics of the adult specimens, but in the nymph stages these characteristics do not allow them to be easily distinguished from other closely related species.
"The results obtained with this technique make possible to unequivocally identify P. spumarius even at immature stages, quickly distinguishing it from close related species," notes Esther Lantero.
This study represents good news for the agriculture and economy. The arrival of the bacterium X. fastidiosa to Europe in 2013 has implied a challenge for the Mediterranean countries that produce olive oil and table olives. In addition to the enormous agricultural losses, there are strict control measures that include the elimination of all plants in a perimeter of 100 metres around the affected plant and the severe treatments with phytosanitary products throughout the entire eradication area, which would be minimised with this technique.
References:
Lantero E. et al. 2018. PCR species specific primers for molecular gut content analysis to determine the contribution of generalist predators to the biological control of the vector of xylella fastidiosa. Sustainability. DOI:10.3390/su10072207
