Integrated management of eucalyptus bacterial wilt in Sumatra, Indonesia.

Abstract

Abstract Bacterial wilt is one the most destructive plant diseases and responsible for great losses in eucalyptus plantations worldwide. Since the use of highly productive monoclonal stands became a common practice in forest companies, the industry have experienced severe bacterial wilt outbreaks. Thus, the present study aimed to provide alternative methods that can be incorporated in the management of bacterial wilt of eucalyptus in Sumatra, Indonesia. Pathogen identification with molecular markers, effect of plant propagation on the disease incidence, chemical sterilization of sand beds, antibacterial activity, and genetic resistance of eucalyptus clones were evaluated. Colonies obtained from diseased plants were morphologically indistinguishable, but specific primers 759F/760R and sequencing of 16S ribosomal RNA gene confirmed the pathogen identity as Ralstonia pseudosolanacearum. In-field evaluation showed that plants propagated via mini-cuttings had the highest disease incidence, 16.5%, while the tissue culture plants rooted in-vitro had the lowest disease incidence, 3%. Chemical sterilization of sand beds with NaOCl and H2O2 was effective on reducing bacterial cells by 97 and 42%, respectively. In-vitro assays confirmed the antibacterial activity of oxolinic acid and streptomycin by promoting a clear zone of 1.3 and 1.4 cm in diameter, respectively. The susceptibility to bacterial wilt varied among eucalyptus genotypes, and of the 21 clones tested eight were resistant, nine were moderate and four were susceptible. Therefore, an effective management of eucalyptus bacterial wilt can be achieved by combining all methods used in this study with best practices used in commercial nurseries and plantations.