Alistair McTaggart(alistair.mctaggart@fabi.up.ac.za)

PRESENTED BYMike Wingfield

(mike.wingfield@fabi.up.ac.za)

The global movement of forestry pests and disease

Introduction of a coevolved pathogen, ora host jump of a native pathogen

Wingfield et al. (2015) Science

Acacia mearnsii in South Africa• Planted on 100,000

hectares in South Africa• Pulp and tannins

• Very few diseases• Most recent new disease

report Ceratocystis albifundus(1993)

• Outbreak of new symptomsin 2013• Slime and exudate• Stunting• Caused by rust

Slime symptoms on Acacia mearnsii

Uredinia Spermogonia

Uromycladium in South Africa• Two species of

Uromycladium are reportedfrom South Africa

• U. tepperianum• Biological control agent

introduced against A. saligna

• U. alpinum• Reported from minor

symptoms on A. mearnsii in1988

• Identification based onurediniospores

Galls and teliospores of U. tepperianum

Urediniospores on Acacia mearnsii• Urediniospores of collections in KwaZulu Natal were

morphologically similar to the first description of U. alpinum inSouth Africa (Morris et al. 1988)

Original collection of U. alpinumfrom Western Cape (PREM 48897)24–40 × 14–20 µm

Rust from KwaZulu Natal andWestern Cape(27–)32–48 × 16–26 µm

Teliospores• Species of Uromycladium are

differentiated by theirteliospores• Number of fertile cells• Presence/absence of vesicle

• The telia of rust on A.mearnsii in KZN appear aspowdery patches on stems,petioles, leaves and fruits

• The teliospores have twofertile cells and the vesicle iseither collapsed or absent

• Molecular data indicated theteliospores from KZN wereconspecific withurediniospores from the Cape

Teliospores of Uromycladium on A. mearnsii

SAR003 U. acaciae on A. mearnsiiSAR008 U. acaciae on A. mearnsii

SAR009 U. acaciae on A. mearnsiiSAR001 U. acaciae on A. mearnsii

SAR002 U. acaciae on A. decurrens

SAR017 U. acaciae on A. mearnsii

SAR015 U. acaciae on A. mearnsiiSAR016 U. acaciae on A. mearnsii

SAR019 U. acaciae on A. mearnsiiBRIP59239 U. acaciae on A. mearnsiiBRIP60092 U. acaciae on A. mearnsii

BRIP56551 U. maritimum on A. thomsoniiBRIP56556 U. maritimum on A. longifolia

DQ323921 U. fusisporumKJ632991 U. fusisporum on A. salicina

MEL235762 U. naracoortensis on A. iteaphyllaBRIP61598 U. naracoortensis on A. dealbata

KJ632990 U. simplex on A. pycnanthaKJ632977 U. tepperianum on A. acuminataKJ632978 U. tepperianum on A. acuminataKJ632985 U. tepperianum on A. salignaKJ632988 U. tepperianum on A. salignaKJ632981 U. tepperianum on A. leiocalyxKJ632982 U. tepperianum on A. leiocalyx

KJ632973 U. falcatarium on Paraserianthes falcatariaKJ632974 U. falcatarium on P. falcataria

KJ632992 U. notabile on A. dealbataKJ632989 U. robinsonii on Acacia melanoxylon

KJ862348 Ravenelia neocaledoniensis on Valchellia farnesiana

KZN

Cape

Australia

8891

100

100

74

100

100

85

Phylogram obtained from ML searchof ITS and LSU regions of rDNA

Uromycladium acaciae has been presentin South Africa for over 20 years• The original collection of Uromycladium alpinum and the

recent outbreaks of U. acaciae are conspecific• This pathogen has been in South Africa since 1988• Uredinial stage caused minor leaf symptoms

• This taxon is best named U. acaciae based onmorphology

• The telial stage causes severe symptoms• It is unknown why this stage was produced• Future studies will investigate the conditions that produced this

stage

McTaggart et al. 2015. Australasian Plant Pathology (in Press).

Observed life cycle of U. acaciae

Uredinia

Telia

Spermogonia, on uppersurface of leaflet

Basidium, germinatesfrom teliospore withone basidiospore

Future research• Why was there a change in

lifecycle of U. acaciae?• Can the lifecycle be

targeted to control thisrust?

• What is the populationdiversity of U. acaciae inSouth Africa?

• Are lifecycles plastic inother rust fungi?

Telia of U. acaciae associated withspermogonia

Calibrated to Acacia

Calibrated to Acacia

Calibrated to Angiospermsor Gymnosperms

Host jumps shaped the diversity ofextant rust fungi

• Rust fungi evolved more recently than previously thought• Previous estimates were based on coevolution of rust fungi with

their hosts

• The most recent common ancestor of rusts had a meanage 113–115 million years ago

• The familial position of Puccinia psidii (rust of Myrtaceae)was resolved in the Sphaerophragmiaceae

McTaggart et al. (2015) New Phytologist

Keeping trees healthy Keeping trees healthy Keeping trees healthy