Occurrence of Calonectria leaf blight in Eucalyptus benthamii progenies and potential for disease resistance

Abstract

Leaf blight caused by the fungi of the genus Calonectria represents a high economic risk for forestry companies due to the high potential of economic damage to commercial eucalyptus plantations. An outbreak of leaf blight was observed in Eucalyptus benthamii progeny in three sites in Southern Brazil. This study aimed to: (i) identify the causal agents of the disease; (ii) quantify the incidence and severity of leaf blight (CLB), and (iii) evaluate the selection for CLB resistance potential of E. benthamii. The incidence of the disease was 100% and severity progressed over time, causing more than 50% of canopy defoliation in most trees. The fungal species associated with this study were C. metrosideri and C. spathulata, both found to be pathogenic; C. spathulata was the most aggressive. Infection of E. benthamii by these fungi was associated with temperatures around 18 °C and relative humidity of approximately 74%. There is sufficient genetic variability for the selection of resistant E. benthamii progenies to CLB, based on low severity degrees.