Diversity of endophytic yeasts from sweet orange and their localization by scanning electron microscopy.
Endophytes are microorganisms that colonize plant tissues internally without causing harm to the host. Despite the increasing number of studies on sweet orange pathogens and endophytes, yeast has not been described as a sweet orange endophyte. In the present study, endophytic yeasts were isolated from sweet orange plants and identified by sequencing of internal transcribed spacer (ITS) rRNA. Plants sampled from four different sites in the state of São Paulo, Brazil exhibited different levels of CVC (citrus variegated chlorosis) development. Three citrus endophytic yeasts (CEYs), chosen as representative examples of the isolates observed, were identified as Rhodotorula mucilaginosa, Pichia guilliermondii and Cryptococcus flavescens. These strains were inoculated into axenic Citrus sinensis seedlings. After 45 days, endophytes were re-isolated in populations ranging from 10(6) to 10(9) CFU/g of plant tissue, but, in spite of the high concentrations of yeast cells, no disease symptoms were observed. Colonized plant material was examined by scanning electron microscopy (SEM), and yeast cells were found mainly in the stomata and xylem of plants, reinforcing their endophytic nature. P. guilliermondii was isolated primarily from plants colonized by the causal agent of CVC, Xylella fastidiosa. The supernatant from a culture of P. guilliermondii increased the in vitro growth of X. fastidiosa, suggesting that the yeast could assist in the establishment of this pathogen in its host plant and, therefore, contribute to the development of disease symptoms.
Departamento de Genética, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Piracicaba, SP, Brazil.
Cláudia Santos
CS
Gai
Paulo Teixeira
PT
Lacava
Walter
W
Maccheroni
Chirlei
C
Glienke
Welington Luiz
WL
Araújo
Thomas Albert
TA
Miller
João Lúcio
JL
Azevedo
D001938:Brazil; D032084:Citrus sinensis / Q000382:microbiology*; D003454:Cryptococcus / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism / Q000648:ultrastructure; D003470:Culture Media; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D003627:Data Interpretation, Statistical; D017343:Genes, Plant / Q000235:genetics; D054884:Host-Pathogen Interactions; D008855:Microscopy, Electron, Scanning / Q000379:methods; D010802:Phylogeny; D010843:Pichia / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism / Q000648:ultrastructure; D010935:Plant Diseases / Q000382:microbiology; D018515:Plant Leaves / Q000382:microbiology; D018517:Plant Roots / Q000382:microbiology; D018547:Plant Stems / Q000382:microbiology; D012248:Rhodotorula / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism / Q000648:ultrastructure; D044167:Xylella / Q000254:growth & development / Q000378:metabolism; D015003:Yeasts / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure*
D003470:Culture Media; D021903:DNA, Ribosomal Spacer