Bacterial wilt: pathogen spread and disease effects on the eucalyptus cloning

This work was aimed to study the Ralstonia solanacearum spread through clonal propagation and to evaluate the bacterial wilt effects on the productivity of cloning process. Samples of mini-stumps, mini-cuttings, and clonal seedlings of seven eucalyptus clones were evaluated regarding to bacterial infections. In a specific experiment, rooting substrate was evaluated to the source of pathogen inoculum. At monthly intervals, the rooting average and productivity index (IP) were determinate in order to evaluate the disease effects on the mini-stumps productivity. The bacterial pathogen was observed on mini-stumps of five clones, while the clonal seedlings of all seven clones showed the disease. This difference was shown to be related to pathogen spread and to disease transmission, which took place during the eucalyptus cloning process. The rooting substrate was efficient to bacterial pathogen survival and as inoculum source to the disease. The symptomless clonal seedlings with systemic infection proved the potential of pathogen transmission to the field in eucalyptus clonal propagation system. The physiologic stresses caused by bacterial infections reduced by four times the IP of mini-clonal hedges. The practices adopted were efficient to permit eradication of disease on the nursery and to avoid the pathogen spread to the field.

Ralstonia solanacearum; Cloning seedlings; Systemic disease