Characterization of an aberrant population of Brevipalpus californicus and its role as a vector of citrus leprosis viruses

A morphometric and molecular characterization of Brevipalpus sp. close to the group of cryptic species within Brevipalpus californicus s.l. bearing only one solenidion on tarsus II was conducted, and its capacity to acquire and inoculate citrus leprosis virus C (CiLV-C) and orchid fleck virus, strain-citrus (OFV-citrus), was determined. For the morphometric study, photomicrographs of mites from two colonies kept in the laboratory were taken: one derived from a single female of the aberrant Brevipalpus that was collected on citrus in Tetipac, Guerrero State, Mexico and provisionally designated as Brevipalpus sp. (Tetipac); another derived from a single female collected in Texcoco, Mexico State [hereafter, B. californicus (Texcoco)]. The observed characteristics were compared with slide-mounted specimens of B. lewisi McGregor and B. californicus Baker from their respective type series. From specimens of each species, 37 morphometric characters were evaluated and compared using univariate and multivariate analysis (principal components and clusters). In the molecular characterization, specimens of Brevipalpus sp. (Tetipac) and B. californicus (Texcoco) were used. Phylogenetic analyses were conducted based on two segments of the COI and one of the 28S genes. Acquisition and inoculation tests of CiLV-C and OFV-citrus were carried out using larvae, nymphs, and adult females of Brevipalpus sp. (Tetipac), on the indicator plants Phaseolus vulgaris L. (Fabaceae), Arabidopsis thaliana (L.) Heynh. (Brassicaceae), and sweet orange [Citrus x sinensis (L.) Osbeck. ‘Valencia’; Rutaceae]. In this last host, B. californicus (Texcoco) and B. yothersi were added as controls. To detect these viruses, specific primers for each of them were used. Univariate analyses showed that only 17 morphological characters were significantly different among mite species. The multivariate analysis showed that Brevipalpus sp. (Tetipac) and B. californicus (Texcoco) are not separate entities; therefore, both were determined as B. californicus s.l. The molecular characterization showed similar results. In the acquisition tests, only two of the 90 replicates were positive for CiLV-C, whereas 84 of the 90 replicates were positive for OFV-citrus. In the inoculation tests, symptoms did not appear in the indicator plants A. thaliana and P. vulgaris after being infested with Brevipalpus sp. (Tetipac) carrying the OFV-citrus. Small nuclear-leprosis-like lesions were only observed on C. sinensis after infestation by viruliferous Brevipalpus sp. (Tetipac). However, RT-PCR did not confirm the presence of OFV-citrus in these plants. In contrast, control plants infested with viruliferous B. californicus (Texcoco) developed leprosis symptoms and the presence of OFV-citrus was confirmed by RT-PCR.