Penetration and favorable conditions to infection of Cylindrocladium pteridis in eucalypt / Penetração e condições favoráveis à infecção de Cylindrocladium pteridis em eucalipto

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The effects of inoculum concentration, duration of leaf wetness period, plant age, and stem position on the severity of leaf spot and defoliation caused by Cylindrocladium pteridis in eucalypts were assessed in greenhouse studies using two hybrid clones of Eucalyptus grandis x E. urophylla. The pattern of adhesion, germination, and penetration of the pathogen in eucalypts leaf was evaluated trough Scanning Electronic Microscopy (SEM). In the experiments of inoculum concentration, wetness period, and plant age, defoliation was not observed in the median and apical parts of the plants. Therefore only the values of defoliation on the lower part of plants were analyzed. Since young leafs showed low values of affected leaf area, disease severity was assess on the second completely expanded leaf pair counted from the base to the top of the main twig of the basal third part of the plant. The values of affected leaf area and defoliation increased as inoculum concentration increased from 1x102 to 1x105 conidia/ml, in both clones. Disease severity also increased as time of leaf wetness duration increased from 6 to 48h. Disease severity was also significantly higher on older plants. Twig position in plants affected significantly the values of affected leaf area and defoliation. Defoliation was significantly higher at stem base tending to zero to the apex, in both clones. As observed for defoliation, the highest values of affected leaf area were observed at stem base, in both clones. The Pearson correlation between defoliation and affected leaf area was significantly in all experiments (r >0,8) showing high association between this two variables. Scanning Electronic Microscopy (SEM) showed that the penetration of C. pteridis in eucalypts leafs occurs through stomata. No differences in the number of penetration between young and old leaves were found. The results of the present study showed that this fungus penetrates eucalyptus leaves typically by stomata and in studies of this patosystem, one should use inoculum suspension at 1x104 conidia/ml, 48 of mist chamber, ≥ 120 day old plants, and score defoliation at the third basal part of the plants.

ASSUNTO(S)

pathogenesis eucalyptus forest pathology fitopatologia patogênese patologia florestal cylindrocladium pteridis cylindrocladium pteridis eucalyptus

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