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Variability of Brevipalpus mites and their ability to transmit viruses: production and maintenance of isoline colonies, identification of mite vectors species and transmission assays of viruses transmitted by Brevipalpus (BTV)

Grant number: 17/18911-0
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): November 01, 2017
Effective date (End): October 31, 2018
Field of knowledge:Agronomical Sciences - Agronomy - Plant Health
Principal Investigator:Elliot Watanabe Kitajima
Grantee:Vanessa Bassinello
Home Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
Associated research grant:14/08458-9 - Plant viruses transmitted by Brevipalpus mites (Acari: Tenuipalpidae) - BTV: survey, identification, molecular characterization, phylogeny; virus/vector/host relationhip; biology, taxonomy and management of the mite, AP.TEM

Abstract

In recent years, knowledge about the viruses transmitted by Brevipalpus (Tenuipalpidae) mites (BTV) had significant advances. BTV have deserved attention not only because some of them as those causing citrus leprosis, coffee ringspot, orchid fleck and green spots of passion fruit are of economical importance, but also because they constitute a peculiar pathosystem causing only localized infection. Furthermore it was found that at least two copletely distict types of BTV being transmitted in a persistent manner: Cilevirus- with a ssRNA, positive sense, bipartite genome Dichorhavirus- ssRNA, negative sense, bipartite genome. On the other hand, taxonomy of Brevipalpus mites underwent important changes recently. Of more than 200 species of Brevipalpus, only three were considered vectors: B. californicus, B. obovatus and B. phoenicis. However new morphological and molecular criteria indicated that the species B. phoenicis l.s. should be composed of at least seven species. This required and reevaluation of the vectors considered as B. phoenicis s.l. Thus CiLV-C is transmitted by B. yothersi, CoRSV,by B. papayensis, CiLV-N, by B. phoenicis s.s. A new BTV found causing chlorotic spots on citrus, had the vector identified as B.aff yothersi, possibly B. incognitus. Another important observation was that as a general rule, plants when infested by Brevipalpus mites, these populations are indeed a mixture of distinct species of this genus. Sucha a situation complicates the determination of the specie(s) transmitting a given BTV, to understand its epidemiology and develop integrated management program.The present project aims to contribute to solve such a situation, through the experimental production of isolines of different Brevipalpus species, properly identified morphologically and by molecular means, and evaluated for their ability to transmit distinct BTV, within the experimental possibilities and also, establish the vector-virus relationship parameters. The chosen model is to use common bean plantlets to colonize Brevipalpus isolines and also to use them as indicator plant for the infection by most of BTV under research. The use of isolines is based on the knowledge that most Brevipalpus species reproduce by telythokous parthenogenesis, in which female begets female, producing quasi-clonal generations. This is a consequence of the infection of these Brevipalpus species by an endosymbiont bacterium, Candidatus Cardinium, which induces the feminilization of haploid forms. This project seens syutable if a scientific initiation program, introducing practices of Brevipalpus mites handling and colonization, identification of Brevipalpus species by light and electron microscopy, BTV transmission assays, etc. These works will include basic concepts of plant pathology, virology, acarology, celular and molecular biology. This project is related to a thematic project on BTV (proc. Fapesp 2014/08458-9) in the subprojects 3 and 4. The candidate student has excellent scholar records and has an international experience in the program Science without Frontiers. (AU)