No abstract

Demethylation inhibitor (DMI) fungicides are used to control brown rot in stone fruit worldwide. However, their specific mode of action can select resistant isolates of Monilinia fructicola. Monilinia fructicola resistant to DMI fungicides are associated with a fitness cost in the absence of selective pressure, indicating that the sensitive population can be re‐established when discontinuing the fungicide in the field. This work aimed to build up the sensitive population of M. fructicola after discontinuing the use of tebuconazole for successive crop seasons. The sensitivity of M. fructicola to tebuconazole was assessed in four commercial peach orchards in Paraná and São Paulo States from 2012/13 to 2015/16. Different fungicide programmes were used and DMI fungicides were discontinued from 2013/14. The sensitivity of M. fructicola to tebuconazole was assessed by a mycelial growth assay in vitro and by determining the frequency of the G461S mutation in the MfCYP51 gene. The isolates from Paraná had high sensitivity to the fungicide across all seasons and the frequency of the G461S mutation remained below 5%. The isolates from São Paulo were highly resistant in the 2012/13 season; however, there was a gradual decline until 2015/16. In addition, the G461S mutation frequency in Sao Paulo State was about 80% in the 2012/13 season, but reduced until it was completely undetectable in 2015/16. These results provide evidence that resistance can be managed in orchards with high selective pressure to tebuconazole after discontinuing the use of the fungicide for at least 3 years.

Xylella fastidiosa is a vector-borne bacterium that causes diseases in many plants of economic interest. The bacterium–vector initial interactions involve bacterial membrane-bound adhesins that mediate cell attachment to the foregut of insect vectors. We investigated the role of the afimbrial adhesin XadA2 in the binding and biofilm formation of X. fastidiosa subsp. pauca to vector surfaces in vitro, as well as its potential to disrupt pathogen transmission. We showed that XadA2 has binding affinity for polysaccharides on sharpshooter hindwings, used as a proxy for the interactions between X. fastidiosa and vectors. When in a medium without carbon sources, the bacterium used wing components, likely chitin, as a source of nutrients and formed a biofilm on the wing surface. There was a significant reduction in X. fastidiosa biofilm formation and cell aggregation on vector wings in competition assays with XadA2 or its specific antibody (anti-XadA2). Finally, pathogen acquisition and transmission to plant were significantly reduced when the vectors acquired X. fastidiosa from an artificial diet supplemented with anti-XadA2. These results show that XadA2 is important in mediating bacterial colonization in the insect and that it could be used as a target for blocking X. fastidiosa transmission.

N-actilcisteína em estudos de transmissão de Xylella fastidiosa por cigarrinhas / Karla Kudlawiec --versão revisada de acordo com a resolução CoPGr 6018 de 2011. --Piracicaba , 2021. 75 p. Dissertação (Mestrado) --USP / Escola Superior de Agricultura "Luiz de Queiroz". 1. Clorose variegada dos citros 2. Vetor 3. NAC 4. Controle I. Título AGRADECIMENTOSAgradeço a Deus por nortear meus caminhos... Agradeço aos meus pais por todo apoio, amor e dedicação e a toda minha família que eu amo e admiro muito.À minha irmã Carol por ser minha parceira de vida e por estar sempre ao meu lado em todos os momentos.Ao professor João Roberto Spotti Lopes pela orientação e apoio nas decisões ao longo do mestrado.Aos pesquisadores do IAC-Cordeirópolis, Alessandra Alves de Souza e Helvécio Dela-Coletta Filho pela ajuda com o projeto de pesquisa e pela orientação no desenvolvimento do projeto.Ao Dr Alberto Fereres, que me recebeu em seu laboratório durante o estágio no exterior e as pesquisadoras Aranzazu Moreno e Elisa Garzo por toda ajuda. Estendo meu agradecimento à técnica María Plaza e ao pós -doutorando Daniele Cornara por todo auxilio. Ao prof Dr. Walmes Zeviani -UFPR pela ajuda com as análises estatísticas.Aos colegas e companheiros que tornaram meus 6 meses em Madri uma experiência enriquecedora profissional e pessoalmente. Alan, Marina, Clara, Elena, Carolina, Cristina, Pierpaolo e Ana, vocês são 10! Os echo mucho de menos! Aos colegas do laboratório de insetos vetores, em especial a Maria Fernanda e a Mariana pela ajuda no decorrer do experimentos. Aos meus amigos, que mesmo com a distância levo comigo Mayara, Gaúcho, Marília, Bianca e Fernanda.Aos colegas da pós-graduação com os quais compartilhei momentos de estudos, apoio e de descontração, em especial à Sabrina, Thais, Matheus e Fernando, que tornaram-se amigos do coração. Incluo aqui a amiga Kelly com quem compartilhei muitos momentos felizes nesta etapa final e a pessoa que foi fundamental para minha evolução pessoal.