Threats

Teratosphearia Leaf Blight / Teratosphaeria destructans

Teratosphearia Leaf Blight / Teratosphaeria destructans
Teratosphaeria destructans (M.J. Wingf & Crous) M.J Wingf. & Crous

Kirramyces destructans M.J. Wingf. & Crous; Phaeophleospora destructans (M.J. Wingf. & Crous) Crous, F.A. Ferreira & B. Sutton; Readeriella destructans (M.J. Wingf. & Crous) Crous & U. Braun

Teratosphaeria destructans is an agressive Eucalyptus leaf blight pathogen. Common symptoms associated with T. destructans are leaf, shoot and bud blight as well as leaf discolouration and malformation (Wingfield et al. 1996; Burgess et al. 2007). Early symptoms on the leaves are chlorotic lesions that progress to large sub-circular brown spots with diffuse borders and red-brown margins (Wingfield et al. 1996; Burgess et al. 2006; Solís et al. 2022). Older leaves exhibit a purple discolouration restricted by veins (Wingfield et al. 1996). The diseased Eucalyptus trees are heavily defoliated, causing a reduction of growth and vigour (Burgess et al. 2006; Dell et al. 2008). In severe cases, the shoots die, resulting in a loss of apical growth (Old et al. 2003). Leaf symptoms are present on both the upper (abaxial) and lower (adaxial) leaf surfaces (Wingfield et al. 1996; Solís et al. 2022). Sporulation of the fungus is typified by tendrils of spores exuding from the stomata on the underside of the leaves (Solís et al.2022). In wet weather, these can coalesce to form plates of black spore masses. 

Slow growing fungus on all media types. Pink-white growth on Malt Extract Agar (MEA) (Greyling et al. 2016).

Asexual structures (pycnidia) form in the stomata on the abaxial (bottom) side of the leaves (Wingfield et al. 1996; Solís et al. 2022). The conidia produced by T. destructans have the longest length range (50-65 μm) of all the Teratosphaeria leaf pathogens (Wingfield et al. 1996; Old et al. 2003; Andjic et al. 2016; Solís et al.2022).

The pathogen infects actively growing young leaves, young shoots and buds (Andjic et al. 2007). The infection occurs via stomata at 48h post inoculation (Solís et al.2022), high levels of humidity are necessary for the disease development (close to 100%) for at least 72 hours post inoculation (Solís et al. 2022) and symptoms are usually visualized at four weeks post inoculation(Solís et al. 2022). 

The sexual state of T. destructans has never been observed, but data from whole genome sequences (Havenga et al. 2020, Wingfield et al. 2018) shows that it has a heterothallic mating system. Individuals are, therefore, either of the MAT1-1 or MAT1-2 type. In populations across five countries in South East Asia, one of the two mating types always dominate. Only MAT1-2 individuals are present in South Africa (Havenga et al. 2020) and these represent a single clone (Havenga et al. in press). In South East Asia, genetic diversity is low (70-90% clonality) and the genetic structure of populations differs among countries (Havenga et al. in press).

The management strategies are based on selection of resistant individuals from the field and at present rely purely on field observations. In FABI we established a method to categorize the host resistance by using artificial inoculations, thus will contribute to reducing the time needed to select individuals for breeding programs (Solís et al. 2022, Accepted- Plant Disease)

 

 

2015 (Greyling et al. 2016)
KwaZulu-Natal, Mpumalanga, Western Cape
The origin of T. destructans is still unknown, but is likely an area where its Eucalyptus hosts are native. Introductions are believed to be a result of human-mediated movement of contaminated plant material (Andjic et al. 2019).

Gallery

Leaf infected by T. destructans
Teratosphaeria destructans leaf blight
Leaf infected by T. destructans
Teratosphaeria destructans leaf blight
Teratosphaeria destructans pycnidium in the stomata of a Eucalyptus leaf
Conidia of Teratosphaeria destructans

Andjic V, Carnegie AJ, Pegg GS, Hardy GESJ, Maxwell A, Crous PW, Pérez C, Wingfield MJ, Burgess TI. 2019. 23 years of research on Teratosphaeria leaf blight of Eucalyptus. Forest Ecology and Management 443: 19-27.

Andjic V, Hardy GE, Cortinas MN, Wingfield MJ, Burgess TI. 2007. Multiple gene genealogies reveal important relationships between species of Phaeophleospora infecting Eucalyptus leaves. FEMS Microbiology Letters 268: 22-33.

Andjic V, Maxwell A, Hardy GE, Burgess TI. 2016. New cryptic species of Teratosphaeria on Eucalyptus in Australia. IMA Fungus 7: 253-263.

Burgess TI, Andjic V, Hardy GESJ, Dell B, Xu D. 2006. First report of Phaeophleospora destructans in China. Journal of tropical forest science 18: 144-146.

Burgess TI, Andjic V, Wingfield MJ, Hardy GESJ. 2007. The eucalypt leaf blight pathogen Kirramyces destructans discovered in Australia. Australasian Plant Disease Notes 2: 141.

Dell B, Hardy GESJ, Burgess T. 2008. Health and nutrition of plantation eucalypts in Asia. Southern Forests: a Journal of Forest Science 70: 131-138.

Greyling I, Wingfield MJ, Coetzee MP, Marincowitz S, Roux J. 2016. The Eucalyptus shoot and leaf pathogen Teratosphaeria destructans recorded in South Africa. Southern Forests: a Journal of Forest Science 78: 123-129.

Havenga M, Wingfield BD, Wingfield MJ, Dreyer LL, Roets F, Chen S, Aylward J. (in press) Low genetic diversity and strong geographic structure in introduced populations of the Eucalyptus foliar pathogen Teratosphaeria destructans. Plant Pathology Accepted Author Manuscript. doi:10.1111/ppa.13235.

Havenga M, Wingfield BD, Wingfield MJ, Roets F, Dreyer LL, Tatham CT, Duong TA, Wilken PM, Chen S, Aylward J. (2020) Mating strategy and mating type distribution in six global populations of the Eucalyptus foliar pathogen Teratosphaeria destructans. Fungal Genetics and Biology 137: 103350.

Old KM, Wingfield MJ, Yuan ZQ. 2003. Phaeopleospora leaf diseases. In: A manual of diseases of Eucalypts in South-East Asia. Indonesia: Center for International Forestry Research, 25-31.

Wingfield MJ, Crous PW, Boden D. 1996. Kirramyces destructans sp. nov., a serious leaf pathogen of Eucalyptus in Indonesia. South African Journal of Botany 62: 325-327.

Wingfield BD, Liu M, Nguyen HD, Lane FA, Morgan SW, De Vos L, Wilken PM, Duong TA, Aylward J, Coetzee MPA. 2018. Nine draft genome sequences of Claviceps purpurea s. lat., including C. arundinis, C. humidiphila, and C. cf. spartinae, pseudomolecules for the pitch canker pathogen Fusarium circinatum, draft genome of Davidsoniella eucalypti, Grosmannia galeiformis, Quambalaria eucalypti, and Teratosphaeria destructans. IMA Fungus 9: 401.

Havenga, M., Wingfield, B. D., Wingfield, M. J., Marincowitz, S., Dreyer, L. L., Roets, F., ... & Aylward, J. (2021). Genetic recombination in Teratosphaeria destructans causing a new disease outbreak in Malaysia. Forest Pathology, 51(3), e12683.

Solís, M., Wingfield, M. J., Hammerbacher, A., & Naidoo, S. (2022). Comparison of the Infection Biology of Teratosphaeria destructans and Teratosphaeria epicoccoides on Eucalyptus. Plant Disease, 106(7), 1944-1951.