Effects of radiation (Cobalt-60) on the elimination of Brevipalpus phoenicis (Acari: Tenuipalpidae) Cardinium endosymbiont

Abstract

Brevipalpus phoenicis (Geijskes) (Acari: Tenuipalpidae) is a polyphagous mite with worldwide distribution and it is also a vector of several plant viruses. In citrus, B. phoenicis transmits Citrus leprosis virus (CiLV), the causal agent of leprosis, a disease that costs millions of dollars per year for its prevention and control. Brevipalpus phoenicis mites reproduce through thelytokous parthenogenesis, producing haploid females. This characteristic is attributable to the presence of an endosymbiont bacterium of the genus Cardinium; however, very little is known about the biological and ecological implications of the presence of this endosymbiont in Brevipalpus mites. In order to investigate the role of Cardinium in the transmission of CiLV to citrus plants, our goal was to eliminate the bacterium from the mite. We assessed the effectiveness of different doses of radiation from a Cobalt-60 source to cure B. phoenicis populations from Cardinium sp. The efficiency of irradiation on the elimination of the endosymbiont was determined by counting the number of females and males obtained in the F(1) generation after irradiation and confirming the presence of the endosymbiont by PCR. Both radiation treatments influenced the oviposition period and the number of eggs laid by irradiated females. Also, irradiation eliminated the Cardinium endosymbiont and increased the number of males in progeny of the exposed populations. Although macroscopic morphological abnormalities were not observed among the treated mites, the mortality was higher compared to the non-irradiated control group.