Àcars en cítrics: defensa de les plantes i interacció del microbioma

Abstract

catalaEn la present tesi doctoral es van analitzar els mecanismes de defensa indirecta de dos patrons de citrics amb diferent nivell de susceptibilitat per a l’herbivor Tetranychus urticae (el mes resistent, Citrus aurantium, i el mes susceptible, C. reshni) mitjancant assajos de comportament amb els tres depredadors fitoseids de l’aranya amb diferents nivells d’especialitzacio en la seua dieta. Tambe, s’han caracteritzat els volatils associats a l’aranya roja i al mandariner Cleopatra induit pels volatils del bord infestat. En segon lloc, s’ha aprofundit en l’estudi de l’aranya roja, estudiant el seu microbioma, ja que s’ha demostrat que els bacteris simbionts poden influir en els parametres biologics dels artropodes, sent una de les especies bacterianes mes importants Wolbachia spp. Finalment, s’ha caracteritzat la resposta dels dos genotips de citrics a la infestacio de Polyphagotarsonemus latus per dilucidar les defenses, el perfil volatil i els mecanismes moleculars implicats en aquesta interaccio. EnglishIn the present doctoral thesis, the defensive response of citrus to two phytophagousmite species, the two-spotted spider mite Tetranychus urticae and the broad mite, Polyphagotarsonemus latus, has been studied, as well as the interaction of the main natural enemies of the two-spotted spider mite. In addition, the study of the microbiome of this phytophagous has been carried out to determine its composition as well as the role of symbiont bacteria. First of all, the mechanisms of indirect defense of two citrus rootstocks with different levels of susceptibility to the herbivore T. urticae (the most resistant, sour orange Citrus aurantium, and the most susceptible, Cleopatra mandarin C. reshni) were analyzed. To do this, a series of behavioral tests were conducted with three phytoseiid predator species of the spider mite with different diet levels of specialization to determine the role of herbivory-induced volatiles plant (HIPVs) in the citrus indirect defense. Moreover, volatiles associated with the spider mite and Cleopatra mandarin induced by T. urticae-infested sour orange have been characterized. Although the preference for less defended plants with presumably more prey density was expected, the response of the three phytoseiid mites studied depends on the plant genotype, the presence of the prey and their feeding habits. Secondly, the study of the key pest T. urticae has been deepened, specifically studying its microbiome, since it has been shown that symbiont bacteria can influence the biological parameters of arthropods. One of the key species is Wolbachia, which is part of a group of intracellular proteobacteria capable of manipulating the reproduction of their hosts. The microbiota characterization of T. urticae could provide new biological control strategies. For doing this, the bacterial community has been analyzed by massive sequencing of the 16S rDNA of two related subpopulations of T. urticae (treated and not treated with tetracycline antibiotic) from a clementine orchard in the region of La Plana maintained as lab strain. Mating assays have been performed between these two lines to determine the effect of the microbiota on the reproduction of the herbivore. The results show how the Wolbachia specie is the most abundant, it can be removed by the antibiotic and this bacterium induces cytoplasmic incompatibility affecting the reproduction of the mite. Finally, the response of the two citrus genotypes has been characterized when they are infested by P. latus to elucidate the defenses, the volatile profile and the molecular mechanisms involved in this interaction. The results demonstrate that the response of citrus to P. latus depends on the plant genotype and affects, at least, the expression of the main defensive pathways genes, that are, jasmonic (JA) and salicylic acid (SA) and the profile of released volatiles. Curiously and contrary to what happens with T. urticae, Cleopatra mandarin sustains lower P. latus populations compared with sour orange. The characterization of these effects can help improve current control practices against this pest.