Susceptibility of South African native conifers to the pitch canker pathogen, Fusarium circinatum

AbstractFusarium circinatum is an economically important pathogen of Pinus species, which also occurs on Douglas fir (Pseudotsuga menzeisii). It causes pitch canker of mature trees and root and collar rot of seedlings and cuttings. In 2007, pitch canker was observed on Pinus radiata in the Western Cape and this was the first outbreak of this disease in South Africa. The Cape flora in this area includes native coniferous species of Podocarpus and Widdringtonia. In this study, seedlings of P. latifolia, P. elongatus, P. henkelii, W. schwartzii, W. cederbergensis and W. nodiflora were inoculated with a virulent isolate of F. circinatum, to assess their susceptibility. Six weeks after inoculation, there was no lesion development in any of the species inoculated. Pinus patula seedlings used as a positive control were severely affected. Results of this study show that species of Podocarpus and Widdringtonia, native to the Western Cape, are not threatened by the pitch canker fungus

Sphaeropsis sapinea and Botryosphaeria dothidea endophytic in Pinus spp. and Eucalyptus spp. in South Africa

Sphaeropsis sapinea (Fr.: Fr.) Dyko & B. Sutton and the anamorph of Botryosphaeria dothidea (Moug.) Ces. et De Not. are morphologically and ecologically similar fungi that cause serious canker and die-back diseases of Pinus and Eucalyptus spp. respectively in South Africa. In this article, the presence of both these fungi as symptomless endophytes In healthy pine and eucafypt tissue was demonstrated. Sphaeropsis sapinea was present in 50% of young, green P patula Schl. et Cham., and 90% of P. radiata D. Don cones. In contrast, it was virtually absent from the cones of P. elliottii Engalm. et Vasey and P. taeda L. Botryosphaeria dothidea, on the other hand, was found to be common in all the Eucalyptus spp. tested, occurring in 93% of E. smithii R. T. Bak., 77% of E. camaldulensis Dehnh., 63% of E. grandis Hill ex Maid, and 57% of E. nitens (Deane et Maid.) Maid, leaves tested. The enigma of the rapid Ingress of both these fungi In stressed or damaged trees might therefore be explained by their endophytic habit

Two new Phytophthora species from South African Eucalyptus plantations

A recent study to determine the cause of collar and root rot disease outbreaks of cold tolerant Eucalyptus species in South Africa resulted in the isolation of two putative new Phytophthora species. Based on phylogenetic comparisons using the ITS and β-tubulin gene regions, these species were shown to be distinct from known species. These differences were also supported by robust morphological characteristics. The names, Phytophthora frigida sp. nov. and Phytophthora alticola sp. nov. are thus provided for these taxa, which are phylogenetically closely related to species within the ITS clade 2 (P. citricola, P. tropicali and P.multivesiculata) and 4 (P. arecae and P. megakarya), respectively. Phytophthora frigida is heterothallic, and produces stellate to rosaceous growth patterns on growth medium, corraloid hyphae, sporangia with a variety of distorted shapes and has the ability to grow at low temperatures. Phytophthora alticola is homothallic and has a slower growth rate in culture. Both P. frigida and P. alticola are pathogenic to Eucalyptus dunnii. In pathogenicity tests, they were, however, less pathogenic than P. cinnamomi, which is a well-known pathogen of Eucalyptus in South Africa

Botryosphaeria eucalyptorum sp. nov., a new species in the B. dothidea-complex on Eucalyptus in South Africa

Two morphologically similar fungi are associated with canker and die-back of eucalypts in South Africa, one of which was identified as part of the Botryosphaeria dothidea-complex. In this study, the identity of the other fungus was determined by comparing morphology, pathogenicity and DNA sequence analysis of isolates of both taxa. Based on these results, a new species, Botryosphaeria eucalyptorum, and its anamorph Fusicoccum eucalyptorum, are described. Although the teleomorph is morphologically similar to other taxa in the B. dothidea-complex, conidial characteristics of the anamorph are distinct, as well as the sequences of the nrDNA internal transcribed spacers ITS1 and ITS2. Like B. dothidea, the fungus is pathogenic to Eucalyptus, although there do not appear to be clear differences in pathogenicity between these two species.Articl

Eucalyptus rust: A disease with the potential for serious international implications

Eucalyptus spp. are propagated extensively as non-natives in plantations in many parts of the tropics and sub-tropics. A number of diseases result in serious losses to this economically important forest resource. Eucalyptus rust, caused by Puccinia psidii, is one such example. The economic losses due to this disease the result of infections of seedlings, young trees, and coppice. R psidii occurs predominately in Central and South America, but reports of a similar rust are known from other areas. Eucalyptus rust is a remarkable disease in that the pathogen is not known on eucalypts in their centers of origin. It has apparently originated on native Myrtaceae in South America and is highly infective on some Eucalyptus spp. planted there. R psidii causes one of the most serious forestry diseases in Brazil and is considered to he the most serious threat to eucalypt plantations worldwide. Advances in eucalyptus rust research are reviewed here, with a focus on topics such as distribution, host range, pathogen specialization, symptomatology, etiology, epidemiology, and control.Articl