Pathogenicity of species in Botryosphaeriaceae associated with stem canker on Eucalyptus germplasms in Uganda

Abstract

Botryosphaeria canker is threatening the successful establishment of commercial Eucalyptus plantations in Uganda. This study investigated the pathogenicity of species of Botryosphaeriaceae associated with the canker disease and susceptibility of Eucalyptus grandis W.Hill ex Maiden and its hybrid clones. Molecular characterization of the rRNA internal transcribed spacer (ITS) and β-tubulin gene regions revealed isolates in; Neofusicoccum parvum, Neofusicocum ribis, Neofusicoccum kwambonambiense, Pseudofusicoccum sp. and Lasiodiplodia sp. Pathogenicity of Botryosphaeriaceae isolates was significant (P<0.05) with isolate AS-02 of N. kwambonambiense being the most aggressive and AS-6 of Pseudofusicoccum spp. being the least.  However, with all fungal isolates combined, hybrid clones (Eucalyptus grandis× Eucalyptus urophylla) GU 7 and GU 8 exhibited the highest resistance to the disease and GC 796/2 and F1 (E. grandis from South Africa) were the most susceptible. The information generated in this study should be exploited for sustainable plantation forestry management in the region.