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Digestive remains reveal potential predators of the Xylella fastidiosa vector in the olive grove

Digestive remains reveal potential predators of the Xylella fastidiosa vector in the olive grove

2018/11/10 - From 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) has been able to detect which can be potential predators of the insect vector that transmits the bacterium Xylella fastidiosa, responsible for the death of more than 350 vegetal species, among them the olive tree, the vine or the almond tree.

This bacterium, as recalled by the UCM, is transmitted from diseased to healthy plants through phytophagous vectors of the family of Aphrophoridae insects, having been confirmed the species Philaenus spumarius as a vector in the European Union.

The educational center explained that until now the control of insect populations has been based mainly on treatments with chemical products, however, against these methods are the undesirable effects for the beneficial fauna of the olive grove, the environment and even human health.

"One of the options that could reduce the use of these chemicals is the biological control by potential predators present in agro-ecosystems. And the first step is to know these natural enemies, which are the arthropods which feed from the Xylella fastidiosa vector," said Beatriz Matallanas, researcher at the Department of Genetics, Physiology and Microbiology of the UCM.

The research, published in Sustainability magazine, addresses the problem of specific DNA detection of P. spumarius in the digestive tract of other arthropods. In this way, the potential predators of this species can be reliably identified, something that is practically impossible to determine with the simple observation of the gastric content.

By means of the polymerase chain reaction (PCR) it is possible to detect minute amounts of the vector 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," researcher Carmen Callejas added.

Even immature species
Once the molecular technique was designed, its effectiveness was tested in real conditions. For this, the UCM researchers sampled more than 60 spiders, potential abundant predators during the spring, in olive groves in the southwest of Madrid, near Villarejo de Salvanés, where there was an outbreak of Xylella fastidiosa.

The results showed that 6.34% of the spiders had fed on P. spumarius, a "remarkable sample considering that the abundance of adult specimens of the vector was low given the climatic conditions of the spring of this year 2018".

The advantages of the developed method include reliability and speed, essential in fast management actions in quarantine areas. Traditionally, the identification of the P. spumarius vector has been based on the morphological characteristics of the adult specimens, but in the early stages these characteristics do not allow to distinguish them easily from other closely related species.

"The results obtained with this technique make it possible to unequivocally identify P. spumarius also in immature stages, quickly distinguishing it from other nearby genera", researcher Esther Lantero pointed out.

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