Insect Science (2019) 00, 1–12, DOI 10.1111/1744-7917.12654 ORIGINAL ARTICLE Selection of Bacillus thuringiensis strains in citrus and their pathogenicity to Diaphorina citri (Hemiptera: Liviidae) nymphs S´ ılvia de Oliveira Dorta 1, 2 , Juliana Balbinotte 3 , Rose Monnerat 4 , Jo ˜ ao Roberto Spotti Lopes 3 , Tatiane da Cunha 1, 2 , Odimar Zanuzo Zanardi 5 , Marcelo Pedreira de Miranda 5 , Marcos Antonio Machado 2 and Juliana de Freitas-Ast ´ ua 6, 7 1 Programa de P ´ os-Graduac ¸˜ ao em Microbiologia Agr´ ıcola, Escola Superior de Agricultura Luiz de Queiroz, Universidade de S ˜ ao Paulo, Piracicaba, SP, Brazil; 2 Laborat ´ orio de Biotecnologia, Centro de Citricultura Sylvio Moreira, Instituto Agron ˆ omico de Campinas, Cordeir ´ opolis, SP, Brazil; 3 Laborat ´ orio de Insetos Vetores de Fitopat ´ ogenos, Departamento de Entomologia e Acarologia, Escola Supe- rior de Agricultura Luiz de Queiroz, Universidade de S ˜ ao Paulo, Piracicaba, SP, Brazil; 4 Embrapa Recursos Gen ´ eticos e Biotecnologia, Bras´ ılia, DF, Brazil; 5 Fundo de Defesa da Citricultura (Fundecitrus), Araraquara, SP, Brazil; 6 Embrapa Mandioca e Fruticultura, Cruz das Almas, BA, Brazil and 7 Laborat ´ orio de Bioqu´ ımica Fitopatol ´ ogica, Instituto Biol ´ ogico, S ˜ ao Paulo, SP, Brazil Abstract Bacillus thuringiensis (Bt) toxins are effective in controlling insect pests either through the spraying of products or when expressed in transgenic crops. The discovery of endophytic Bt strains opened new perspectives for studies aimed at the control of sap- sucking insects, such as the Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Liviidae), a vector of “Candidatus Liberibacter spp.,” associated with citrus huanglongbing (HLB). In this study, translocation of endophytic Bt strains in citrus seedlings inoculated with Bt suspension delivered by soil-drench, and their systemic pathogenicity to D. citri nymphs were investigated. The pathogenicity of three wild-type Bt strains against D. citri third-instar nymphs was demonstrated. Among the 10 recombinant strains tested (each of them harboring a single cry or cyt gene), 3 can be highlighted, causing 42%–77% and 66%–90% nymphal mortality at 2 and 5 d after inoculation, respectively. The isolation of Bt cells from young citrus shoots and dead nymphs, and PCR performed with specific primers, confirmed the involvement of the Bt strains in the psyllid mortality. This is the first report showing the translocation of Bt strains from citrus seedling roots to shoots and their potential to control D. citri nymphs that fed on these soil-drench inoculated seedlings. The Bt strains that caused the highest mortality rates have the potential to be used as bioinsecticides to control D. citri and the identified genes can be used for the production of transgenic Bt citrus. Key words Asian citrus psyllid; Citrus sinensis; Cry toxins; endophytic Bt; huanglong- bing; young shoots Correspondence: Juliana de Freitas-Ast´ ua, Embrapa Man- dioca e Fruticultura, Embrapa, Av. Embrapa, s/n, Chapad- inha, Cruz das Almas, BA, 44380-000, Brazil. Phone: +55 61 3448-4433, Fax: +55 61 3448-4890/3448-4891; Email: juliana. astua@embrapa.br Introduction Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a serious threat to citrus produc- tion worldwide, since it is a vector of the phloem-limited bacteria “Candidatus Liberibacter asiaticus” and “Ca. L. americanus” associated with huanglongbing (HLB) C  2018 Institute of Zoology, Chinese Academy of Sciences 1