Characterization of Ceratocystis wilt on Eucalyptus and its causal in Southern Bahia, Brazil

Abstract

Fungi of the Ceratocystis fimbriata complex are important pathogens in woody species, associated with symptoms of wilt, stem lesions and death of infected plants. In Eucalyptus plantations, these pathogens can reduce productivity and cause high mortality in the first years of planting. The objective of this work was to evaluate the symptoms and characterize isolates of Ceratocystis associated with Eucalyptus plantations in southern Bahia, Brazil. In this study, we observed that external symptoms manifested mainly in trees with up to 36 months of planting; however, asymptomatic diseased trees were found until the end of the cycle (7 years). Symptoms of wilt, wood discoloration, formation of adventitious shoots and bark lesions, and drying of branches and death have been observed in diseased trees. The discoloration of the wood began in the root system, which is probably the point of penetration of the causal agent. Symptoms of heartwood rot, along with the characteristic wood discoloration of Ceratocystis wilt, were observed in some of the diseased trees. Based on the sequencing of the rpbII, ms204 and bt1 gene regions, the Ceratocystis isolates obtained from diseased trees were identified as belonging to the species C. manginecans. The morphological characteristics and optimal development temperature of the studied isolates are consistent with those described in the literature for this pathogen. Although collected from geographically close locations, the Ceratocystis isolates studied exhibited different levels of aggressiveness against Eucalyptus clones. This result illustrates the difficulty in selecting materials resistant to Ceratocystis wilt. The present work improves the understanding of Ceratocystis wilt in Eucalyptus and its causal agent.