Comparison of procedures to evaluate the pathogenicity of Ceratocystisfimbriata sensu lato isolates from Eucalyptus in South Africa

Abstract

Ceratocystis fimbriata sensu lato (s.l.) is an important pathogen of Eucalyptus. Pathogenicity of isolates has typically been evaluated by inoculating seedlings under greenhouse conditions. It is, however, not clear how accurately this reflects pathogenicity under field conditions. In this study, five techniques to potentially screen C. fimbriata isolates for their relative pathogenicity to Eucalyptus were compared. These included: in vitro growth comparisons on artificial media; inoculations on apples; inoculation on Eucalyptus seedlings in a greenhouse; inoculations on Eucalyptus bolts freshly cut from stems of young trees; and field inoculations on young trees. Eight isolates of C. fimbriata s.l. collected from various areas in South Africa were used. There was considerable variation in growth in culture and aggressiveness of the eight isolates. Field inoculations on young trees were best correlated with inoculations of bolts (r = 0.76). Lower correlation coefficients were obtained with seedlings (r = 0.59), apple inoculations (r = 0.56), and in vitro colony growth (r = 0.42). Inoculation of bolts provides a rapid and reliable method to screen isolates of C. fimbriata s.l. for pathogenicity to Eucalyptus.

Ceratocystiswilt and canker – a disease that compromises the growing of commercialAcacia-based plantations in the tropics

“…in South Africa and Uganda , and for A. mangium in Indonesia (Tarigan et al 2011a), Malaysia (Brawner et al 2015) and Vietnam (Thu et al 2012). These symptoms have also been reported for Eucalypts in Africa (Roux et al 2000a;Roux et al 2000b;Roux et al 2001a;Roux et al, 2004b;Van Wyk et al 2010a) and South America (Laia et al 2000;Barnes et al 2003b). The incidence of Ceratocystis disease in Eucalypts in Indonesia is confined to a small number of susceptible clones (Heru Indrayadi pers.…”

Ceratocystis quercicola sp. nov. from Quercus variabilis in Korea

“…However, the preliminary pathogenicity test was conducted on freshly excised Q. variabilis bolts and the results should be interpreted with caution. Ideally, living trees would be inoculated but these could not be sourced and a proxy for pathogenicity [28].…”

Ceratocystis eucalypticola sp. nov. from Eucalyptus in South Africa and comparison to global isolates from this tree

“…Eucalyptus death associated with C. eucalypticola has never been found in South Africa although trees dying of unknown causes are thought to have died due to infection by this fungus, which can be difficult to isolate. The fungus collected from wounds on trees has also been shown to be pathogenic in greenhouse inoculation trials ( Roux et al 2004 , van Wyk et al 2010b ).…”