SA Graan Augustus 2016

Augustus 2016

Fusarium head blight incidence

is on the rise, globally

ecently, research staff from the

ARC-Small Grain Institute (ARC-

SGI) had the privilege of attending

the 5

International Symposium

on Fusarium head blight (FHB) and se-

cond Wheat Blast Workshop held in Flori-

anopolis, Brazil from 6 to 9 April 2016.

There were 163 delegates (representing

31 different countries) who work only

on Fusarium head blight (

Photo 1

). Over

the four day programme, twelve keynote

speeches and 24 invited oral presenta-

tions were delivered. Two posters display-

ing current research being conducted at

ARC-SGI were presented with the genera-

tion of overwhelming interest during the

one-week conference.

The first poster was on the development

of diverse Fusarium head blight resistant

wheat cultivars and the second on the eval-

uation of scab entries evaluated under field

and glasshouse conditions.

Highlights and things

learnt about Fusarium

head blight

Breeders from a research group in Austria

are making significant progress in further

improvement of Fusarium head blight re-

sistance by looking at selection for taller

mutant varieties containing one or two

dwarfing genes and looking at the trait of

anther retention or extrusion.

From their research, developed lines that

are taller and do not retain the anthers dur-

ing flowering, are preferred during selec-

tion as the data suggests this material is

expected to be more Fusarium head blight

resistant.

In China, the increase in Fusarium head

blight incidence has increased significantly

in the past season with 3 million hectares

of wheat affected primarily due to the large

areas planted to susceptible Fusarium head

blight cultivars and an increase in area

planted in rotation with maize. Currently,

only ten out of 239 wheat cultivars released

in China between 2005 and 2014 have

moderate Fusarium head blight resistance.

Multiple international research groups

around the world are racing to be the first

to clone the

Fhb1

gene (codes for a DNA

binding protein). It was mentioned that sim-

ply having

Fhb1

in the background of mate-

rial can result in 20% to 50% reduction in

Fusarium head blight severity. The outputs

of these research groups were presented

and should be published in the near future.

The

Fhb2

Fhb4

and

Fhb5

genes are current-

ly being fine-mapped by an international

group for the identification of better diag-

nostic gene markers.

Research presented from the USA per-

spective was interesting as Fusarium head

blight is now considered the most economi-

cally important disease on wheat and bar-

ley. An increase in Fusarium head blight

incidence in the USA has been attributed

to a number of things (especially since

2013) namely, more irrigated wheat in rota-

tion with maize, integrated with the dairy

industry.

There has been a boom in craft breweries

in the USA, now with over 3 000 small

breweries established, using 35% more bar-

ley malt. The increase in barley production

has also had a significant effect on Fusarium

head blight incidence.

In general

The same reasons for Fusarium head

blight increase mentioned before were rein-

forced: Changing weather patterns/climate

change (rain after/around flowering), large

areas of susceptible cultivars planted, in-

crease in maize production and reduced

tillage practices.

It was concluded from an international

viewpoint that conservation agricultural

tillage practices are here to stay and as

Fusarium head blight researchers we must

accept it and come to terms with it. The

international community is encouraged to

work around no-till or reduced tillage sys-

tems, which have more advantages in other

areas of crop production and far outweigh

the risk posed by increased incidence of

Fusarium head blight outbreaks.

Concern was raised following fungicide

testing research conducted by different

groups over several years. These results in-

dicate that fungicides within the strobilurin

group significantly increases Deoxyniva-

lenol (DON) mycotoxin levels (6% - 18%)

in the harvested grain after treatment. The

Fusarium head blight disease symptoms

are suppressed by this fungicide group but

DON production is stimulated by a chemi-

cal-pathogen interaction that is not well

understood yet. This must be noted by the

South African wheat/barley industries if

fungicides become registered for Fusarium

head blight control on these crops in future.

Bt-maize

Unfortunately, another scientifically proven

negative effect of Bt-maize was identified.

From studies done internationally, the stub-

ble of Bt-maize supports the Fusarium head

blight disease complex and makes it more

difficult to control.

As the Bt-maize stubble/residue is damag-

ed to a lesser degree by insects during

the season, there are fewer entry points

(wounds) for microbial activity. As a result,

the Bt-maize stubble breaks down or de-

cays much slower. Maize stubble/residue

can remain the primary inoculum source

for Fusarium head blight infection in the

following crop/season for up to three years.

This situation could be made worse with

Bt-maize.

Producers and researchers need to make

use of an integrated disease management

approach. The best control and yield advan-

tage achieved in multiple studies was when

a moderately resistant cultivar was planted

in combination with fungicide control.

During the conference, a number of new

Fusarium head blight resistant sources

were identified for importation and use in

the current development of diverse Fusar-

ium head blight resistant germplasm at

ARC-SGI, Bethlehem. In certain research

areas, the Fusarium head blight research

conducted at ARC-SGI has closed the recent

gap between international research groups,

especially around pre-breeding for diverse

Fusarium head blight resistant germplasm.

Wheat Blast Workshop

Wheat blast has very similar signs to that

of Fusarium head blight on wheat (

Photo 2

Photo 3a

and

Photo 3b

). Characteristic signs

are silvery white spikes/heads that develop

in patches in the field. Signs may also ap-

pear on the lower leaves.

The canopy of the wheat crop is still green.

Greyish fungal growth can be seen on the

rachis between spikelets on the head. Har-

vested grain from the infected spikes appear

SCOTT SYDENHAM

and

CATHY DE VILLIERS,

ARC-Small Grain Institute, Bethlehem

– Wheat Blast: A scary disease worth noting

ON FARM LEVEL

New wheat disease / Symposium

Integrated pest control