Differences in Selection Behaviors and Chemical Cues of adult Asian Citrus Psyllids, Diaphorina citri, on Healthy and Huanglongbing-Infected Young Shoots of Citrus Plants

Abstract

The pathogen Candidatus Liberibacter asiaticus (Las) causes devastating citrus huanglongbing in many parts of Asia. The host selection behavior of the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Sternorrhyncha: Psyllidae), the only known Las vector, is critical to its epidemics. Las-infected citrus plants attract adult psyllids by altering their color and chemical cues. However, it is unclear whether any changes in selection behavior or chemical cues occur in young shoots. Selection behavior bioassays showed the number of adults and eggs on Las-infected shoots was significantly higher than on healthy shoots. Significantly more adults responded to the odor of Las-infected shoots than to that of uninfected shoots. GC-MS analysis of volatile constituents showed that the quantitatively dominant constituents were β-elemene and β-phellandrene in both samples, (+)-epi-bicyclosesquiphellandrene was only detected in Las-infected shoots, but ocimene, germacrene D, δ-cadinene, d-longifolene, and α-sinensal were detected only in healthy shoots. Analysis of the concentrations of surface-soluble carbohydrates indicated that the levels of sucrose, fructose, and glucose were significantly higher on the surfaces of Las-infected shoots than on the surfaces of healthy shoots. Alteration of volatile compounds and soluble surface carbohydrates of young shoots after Las infection could be attributed to the preference of Asian citrus psyllids for Las-infected young shoots. The knowledge obtained from this investigation may contribute to novel control measures for plant diseases transmitted by insect vectors.

Effects ofCandidatus Liberibacter asiaticuson the fitness of the vectorDiaphorina citri

“…Zhao et al . () revealed that significantly higher populations of eggs and adults were found in Las‐infected shoots than Las‐free shoots of citrus, suggesting that the odours of Las‐infected shoots are more attractive to citrus psyllid than uninfected shoots. Wu et al .…”

The push–pull strategy for citrus psyllid control

“…ACP responded differently to the odour emitted by its host plants. When the host trees were infected by Candidatus Liberibacter asiaticus ( C Las), the number of adults and eggs on symptomatic shoots was significantly higher than on non‐symptomatic shoots . Although C Las‐infected plants were initially more attractive to ACP adults than were non‐infected plants, the non‐infected healthy plants were preferred settling points for the dispersing psyllids after being contracted with HLB bacteria from feeding on diseased trees .…”

Identificação de voláteis de plantas de citros com potencial para uso no manejo integrado de Diaphorina citri Kuwayama (Hemiptera: Liviidae)

“…Tabela 1 -Lista dos compostos químicos encontrados nos extratos de voláteis de plantas de citros sadias e plantas de citros sintomáticas para HLB a Identificação feita pela co-injeção de composto sintético padrão b % em relação a área total dos compostos do tratamento TR = Tempo de reteção; KI = Índice de Kovats; Teste-'t' de Student (*P ≤ 0,05; ** P ≤ 0,01) -CEVALLOS et al, 2011;MANN et al, 2012;ZHAO et al, 2013; HIJAZ; EL-SHESHENY; KILLINY, 2013), os resultados do presente trabalho a primeira evidência experimental de alterações químicas ocorridas em plantas de C. sinensis 'Pêra' enxertada sobre 'limão cravo', que é a principal variedade cítrica dos pomares brasileiros (PIO et al, 2005).…”

“…Para avançar nestes conhecimentos, a resposta comportamental de adultos de D. citri vem sendo investigada frente aos voláteis de diferentes espécies de plantas, fornecendo subsídios importantes para compreensão dos fatores envolvidos nestas interações. Utilizando olfatômetros 'Y', trabalhos recentes demonstraram a resposta olfativa de D. citri para odores de murta e de diferentes espécies de citros (WENNINGER; STELINSKI;HALL, 2009;NORONHA Jr., 2010;SÉTAMOU, 2010;MANN et al, 2012;ZHAO et al, 2013). De acordo com trabalho deWenninger, Stelinski e Hall (2009), machos e fêmeas de psilídeos respondem diferentemente aos mesmos estímulos olfativos, e suas respostas variam para diferentes espécies de plantas hospedeiras.…”

“…Estudos posteriores verificaram que 'VOCs' de plantas de citros foram mais atraentes para os psilídeos frente aos voláteis de plantas de murta(SULE et al, 2012) e que plantas de citros infectadas com Ca. Liberibacter asiaticus foram mais atraentes para adultos de D. citri que os voláteis de plantas sadias(NORONHA Jr., 2010;MANN et al, 2012;ZHAO et al, 2013). Estes resultados demonstram uma estreita evolução destes fitopatógenos com as plantas que o hospedam e seu vetor para seu benefício próprio.Buscando compreender as alterações comportamentais dos psilídeos promovidas pelos odores das plantas hospedeiras, os perfis químicos destas plantas foram investigados em diferentes trabalhos a partir de técnicas diversas, tais como aeração dos 'VOCs' liberados pelas plantas, captura em polímeros adsorventes e eluição com solventes, micro extração de fase sólida (SPME) e extração das moléculas voláteis presentes no conteúdo celular das folhas, com análise destas substâncias em equipamento de cromatografia gasosa acoplado a espectrômetro de massas (GC-MS) (CEVALLOS-CEVALLOS; REYES-DE-CORCUERA, 2008;MANTHEY, 2008;SÉTAMOU, 2010;CEVALLOS-CEVALLOS et al, 2011;MANN et al, 2012;ZHAO et al, 2013;HIJAZ;EL-SHESHENY;KILLINY, 2013).Porém, poucos trabalhos avaliaram a bioatividade de standars (padrões comerciais) para os psilídeos.…”