Fungal canker pathogens on waterberry and Eucalyptus trees in South Africa

Waterberry and Eucalyptus.

Syzygium cordatum, waterberry (Myrtaceae) makes up an integral part of native forest ecosystems in South Africa. Non-native Eucalyptus plantations are mainly established in the eastern part of the country in the same area where closely related S. cordatum is widely spread. Species of Botryosphaeriaceae are canker and die-back pathogens on many forest trees, including Eucalyptus. They can also exist in symptomless plant tissues and as such, move unnoticed into new environments. When non-native trees are planted in the close association with related native trees, pathogens from either of these hosts can potentially cross infect the other host group and potentially cause serious disease problems.

Four species of Botryosphaeriaceae are known as pathogens of Eucalyptus in South Africa. In this study eight species of Botryosphaeriaceae were identified as endophytes on native S. cordatum in South Africa. Pathogenicity trials conducted in greenhouses confirmed that all of these species are potentially pathogenic to Eucalyptus, and thus pose a threat to this tree. The results obtained in this study provide the first detailed information on Botryosphaeriaceae on the native Myrtaceae in South Africa.

Botryosphariaceae on Syzygium and  Eucalyptus.

Draginja Pavlic with S. cordatum.

Our study clearly shows that commercially grown plantations, composed of non-native trees, and their pathogens cannot be viewed separately from the native flora. This study also highlights the need for quarantine measures to avoid the introduction of new species of Botryosphaeriaceae or new strains of these fungi that could be more pathogenic to either native or cultivated hosts. Due to the economic importance of cultivated trees as well as the need to protect native ecosystems, future studies should be focused on pathogens that occur on related native and non-native trees and also on their movement between different host groups.

Related Publications

Pavlic D, Slippers B, Coutinho TA, Gryzenhout M, Wingfield MJ. 2004. Lasiodiplodia gonubiensis sp. nov., a new Botryosphaeria anamorph from native Syzygium cordatum in South Africa. Studies in Mycology 50:313-322.

Pavlic D, Slippers B, Coutinho TA, Wingfield MJ. 2007. Botryosphaeriaceae occurring on native Syzygium cordatum in South Africa and their potential threat to Eucalyptus. Plant Pathology 56:624-636.

Online Interview with Draginja Pavlic

Q: Which part(s) of this study did you enjoy most?

Exploring the “new world” of the native African trees! Collecting samples from these evergreen  trees included a lot of field work mostly in unexplored and protected areas, giving me an opportunity to see the most beautiful and unforgettable places in South Africa and learn about native flora.  Microscopy and identification of all known and new species was the most enjoyable part of the lab work!

Q: Did you experience any difficulties during this study, and if so, how did you overcome them?

We needed Syzygium trees for pathogenicity tests, but did not have them in the FABI Nursery. I then had to collect seeds and used these to establish a Syzygium seedling collection.  We have continued producing these seedlings for use in other studies of Botryosphaeriacea and the other native pathogens.

Q: What happens next? In other words, what still needs to be done and which questions remain unanswered?

There is still lot of work to be done. In this study, some of the pathogens were found for the first time in South Africa and on native waterberry trees and were also found in large numbers. This allowed us to further study populations of these species, and better understand their biology, ecology and potential movement between different hosts.