Figure 1
Hypotheses and strategies to control citrus variegated chlorosis (CVC) using endophytic bacteria from citrus plants. (A) We suggest the endophytic bacterium Curtobacterium flaccumfaciens as a classical biological control agent. C. flaccumfaciens has the ability to colonize plant tissues in the presence or absence of Xylella fastidiosa (Xf). This is a prerequisite for the use of this bacterium as a biocontrol agent. The data indicate that C. flaccumfaciens interacted with X. fastidiosa in Catharanthus roseus and reduced the severity of the disease symptoms induced by X. fastidiosa (Araújo et al., 2002Araújo WL, Marcon J, Maccheroni Jr W, Van Elsas JD and Azevedo JL (2002) Diversity of endophytic bacterial populations and their interaction with Xylella fastidiosa in citrus plants. Appl Environ Microbiol 68:4906-4914.; Lacava et al., 2004Lacava PT, Araújo WL, Marcon J, Maccheroni Jr W and Azevedo JL (2004) Interaction between endophytic bacteria from citrus plants and the phytopathogenic bacterium Xylella fastidiosa, causal agent of citrus variegated chlorosis. Lett Appl Microbio 39:55-59.; Lacava et al., 2007aLacava PT, Li W, Araújo WL, Azevedo JL and Hartung JS (2007a) the endophyte Curtobacterium flaccumfaciens reduces symptoms caused by Xylella fastidiosa in Catharanthus roseus. J Microbiol 45:388-393.; Gai et al., 2011Gai CS, Dini-Andreote F, Andreote FD, Lopes JRS, Araújo WL, Miller TA, Azevedo JL and Lacava PT (2011) Endophytic bacteria associated to sharpshooters (Hemiptera: Cicadellidae), Insect vectors of Xylella fastidiosa subsp. pauca. J Plant Pathol Microbiol 2:102-109.). (B) Additionally, the endophytic bacterium Methylobacterium has been suggested as a qualified candidate for a paratransgenic symbiotic control (SC) strategy because there have been reports on the transmission, colonization and genetic manipulation of Methylobacterium, which are prerequisites for the potential use of this bacteria to interrupt transmission of X. fastidiosa, the bacterial pathogen causing CVC, by insect vectors (Araújo et al., 2002Araújo WL, Marcon J, Maccheroni Jr W, Van Elsas JD and Azevedo JL (2002) Diversity of endophytic bacterial populations and their interaction with Xylella fastidiosa in citrus plants. Appl Environ Microbiol 68:4906-4914.; Andreote et al., 2006Andreote FD, Lacava PT, Gai CS, Araújo WL, Maccheroni Jr. W, Van Overbeek LS, Van Elsas JD and Azevedo JL (2006) Model plants for studying the interaction between Methylobacterium mesophilicum and Xylella fastidiosa. Can J Microbiol 52:419-426.; Lacava et al., 2006aLacava PT, Li WB, Araújo WL, Azevedo JL and Hartung JS (2006a) Rapid, specific and quantitative assays for the detection of the endophytic bacterium Methylobacterium mesophilicum in plants. J Microbiol Methods 65:535-541.; Gai et al. 2009Gai CS, Lacava PT, Quecine MC, Auriac MC, Lopes JRS, Araújo WL, Miller TA and Azevedo JL (2009) Transmission of Methylobacterium mesophilicum by Bucephalogonia xanthophis for paratransgenic control strategy of citrus variegated chlorosis. J Microbiol 47:448-454., 2011Gai CS, Dini-Andreote F, Andreote FD, Lopes JRS, Araújo WL, Miller TA, Azevedo JL and Lacava PT (2011) Endophytic bacteria associated to sharpshooters (Hemiptera: Cicadellidae), Insect vectors of Xylella fastidiosa subsp. pauca. J Plant Pathol Microbiol 2:102-109.; Ferreira Filho et al., 2012Ferreira Filho AS, Quecine MC, Bogas AC, Rossetto PB, Lima AOS, Lacava PT, Azevedo JL and Araújo WL (2012) Endophytic Methylobacterium extorquens expresses a heterologous ß-1,4-endoglucanase A (EglA) in Catharanthus roseus seedlings, a model host plant for Xylella fastidiosa. World J Microbiol Biotechnol 28:1475-1481.).