Fusarium thapsinum is the dominant species associated with sorghum … · 2015-12-09 · Department of Employment, Economic Development and Innovation Fusarium thapsinum is the dominant

Department of Employment, Economic Development and Innovation

Fusarium thapsinum is the dominant species associated with sorghum stalk

rot in Queensland and northern New South Wales

Lisa Kelly, Malcolm Ryley, Elizabeth Aitken, Yu Pei Tan

2© The State of Queensland, Department of Employment, Economic Development and Innovation, 2011

Grain sorghum in Australia• Grown in Qld and NSW mostly under raingrown conditions

• 2.7 million tonnes were produced from 767,000 ha in 2008-09 (ABS 2010)

• Production in Australia is highly variable between seasons largely due to fluctuations in annual rainfall


Sorghum lodgingResults from interactions of:

– Climatic stresses (heat, moisture)

– Anatomical weakness of stalk

– One or more plant pathogens

It causes:

– Harvesting difficulties

– Loss of quantity and quality of grain

– Reduced quantity and quality of fodder

Sam Gall, Pioneer Hi-Bred 2009


The role of physiological stress in lodging• Various factors can affect assimilate supply, such as water deficit,

diseases, insect damage, nutrient imbalance, and light intensity

• The resulting stress is thought to result in a shortage of available carbohydrate in the stem. Cell death and pith disintegration follows, eventually leading to lodging

Sam Gall, Pioneer Hi-Bred 2009Sam Gall, Pioneer Hi-Bred 2009


The role of pathogens in lodging

• Stalk rotting pathogens are often, but not always, associated with lodging

• Major stalk rotting pathogens are:

– Fusarium spp. (fusarium root and stalk rot)*

– Macrophomina phaseolina (charcoal rot) *

– Erwinia chrysanthemi (bacterial stalk rot)

– Colletotrichum graminicola (anthracnose stalk rot)


Common stalk rotting pathogens

• Distinctive symptoms

• Fusarium pathogens of sorghum have a narrow host range

• M. phaseolina has a wide host range

Fusarium sp. Mixed M. phaseolina


Importance of post-anthesis stress

desiccatednot desiccated



Biology of sorghum stalk rotting Fusarium species

• Survive between seasons in plant debris and soil, and on seed and alternative hosts

• Probably infect roots and stems through natural wounds, or injury from insects or machinery and remain latent until stress occurs

• Can also cause root infection of seedlings and older plants, and head blight



Fusarium species - previous findings

• Earlier reports of F. moniliforme sensu lato associated with sorghum most likely refer to F. thapsinum*, F. andiyazi*, F. nygamai, F. proliferatum, and perhaps F. verticillioides

• Petrovic (2007) found F. thapsinum and F. andiyazithe dominant species associated with sorghum in 2 regions in NSW/sth Qld (14 species in total), with differences in dominance, diversity and composition between regions

* Dominant species overseas


Fusarium species – collections

• 2008/09, 2009/10 & 2010/11 collections

• 71 locations; 332 isolates to date

• Stalks, panicles, seedlings, stubble

Central Qld – 8 sites, 23 isolates

Southern Qld – 44 sites, 157 isolates

Northern NSW – 19 sites, 152 isolates


Identification of Fusarium spp.• Morphological features

– Macroconidia & microconidia - morphology, absence/presence, abundance

– Formation of microconidia: conidiogenous cells, chains or false heads

– Chlamydospores: absence/presence, formation

• Secondary characters in vitro– Pigmentation

– Growth rate

• Molecular techniques– Sequencing of the translation elongation factor 1-α gene


Abundance of species

F. thapsinumF. andiyaziF. semitectumF. chlamydosporumF. proliferatumF. oxysporumF. verticillioides

n = 243

Pathogenic species


Geographic distribution of species

(n = 118) (n = 110) (n = 15)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Southern Qld Northern NSW Central Qld

% is

olat

es

F. verticillioidesF. oxysporumF. proliferatumF. chlamydosporumF. semitectumF. andiyaziF. thapsinum

Pathogenic species


Species identified from different sorghum plant parts

F. thapsinum*

F. andiyazi*

F. semitectum

F. chlamydosporum

F. proliferatum*

F. oxysporum*

F. verticillio

ides*stalks

stubbleseedlings

panicles01020

30

4050

60

70

80

90

100

No.

isol

ates

* pathogenic species


Fusarium head blight


Fusarium head blight – infection

• Panicles spray-inoculated with a spore suspension and covered for 48h

• Only those inoculated at 100% flowering produced symptoms

• F. thapsinum and F. andiyazi isolated from stalks were pathogenic on panicles and vice versa

Lisa Kelly, DEEDI


Screening for resistance• Seedlings grown in test tubes, inoculated with an agar plug

• After 10-14 days roots are inspected for discolouration and shoot lengths are measured


Screening for resistance• Roots of all 3 hybrids had red discolouration, no discolouration in

controls• Measured shoot length from seed to developing leaflet (1), and

shoot length from seed to tip of first leaf (2)

0

2

4

6

8

10

12

14

% re

duct

ion

in le

ngth

Hybrid 1 Hybrid 2 Hybrid 3

% reduction (1)% reduction (2)


Summary of findings to date

• F. thapsinum is the dominant species in all regions, followed by F. andiyazi – similar to overseas

• F. verticillioides is of low frequency, F. nygamai not yet identified

• Tested isolates of F. thapsinum and F. andiyazi are pathogenic on seedlings, stalks and panicles

• A seedling test to identify resistant germplasm shows promise


Future activities

• Collect additional isolates from Central Qld*

• Identify remaining isolates*

• Develop protocol(s) to rapidly screen germplasm for resistance to the dominant Fusarium species (seedling/stalk/panicle)*

• Investigate the interactions between the pathogens, stress and stay-green traits

• Investigate potential IDM strategies for the stalk rot pathogens (eg. tillage practices, rotation, resistance)


Acknowledgements• Supervisors Mal Ryley, Agri-Science Qld, and Elizabeth Aitken, UQ

• Yu Pei Tan for assistance with molecular identification

• Funding from the Grains Research and Development Corporation

• Northern Grower Alliance for their collaboration

Mal Ryley, QPI&F 2009

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Fusarium thapsinum is the dominant species associated with sorghum … · 2015-12-09 · Department of Employment, Economic Development and Innovation Fusarium thapsinum is the dominant