Junie 2014
62
ON FARM LEVEL
Pest control
Thisdamage to thegrainwill affect thegrading that canbeobtained,
whichwill significantly influencepotential profits for producers.
Retainedseed infectedwith
Fusarium
could reduceseedgermination
and increase the incidence of root rot and seedling blight as well.
Infected kernels may contain mycotoxins which are produced by
certain
Fusarium
specieswhich are hazardous to humans aswell as
animals after consumption. For this reason,
Fusarium
mycotoxins
have also been studied for their involvement in pathogenicity
(aggressiveness) of the fungus during infection.
The best management method of Fusarium head blight is an
integrated method, involving better management of both crop
rotation and no-till practices, built around the planting of resistant
cultivars. Themost environmentally responsible and efficient long-
termmethod for Fusarium head blight control is resistant cultivars
with host plant resistance. There are different types of Fusarium
head blight resistance which have been documented that make
up the Fusarium head blight disease complex. Type I resistance
provides resistance to initial infection by the pathogen; Type II is
resistanceagainst the spreadof
Fusarium
infectionwithin thewheat
head and the accumulationofmycotoxins such asDeoxynivalenol.
For a number of years a well-documented Fusarium head blight
resistance source, Sumai 3, has been used in several breeding
programmes around the world to provide resistant wheat varieties.
Sumai 3 contains important Fusarium head blight resistance genes/
QTLwhichcanbe targetedwith specificDNAmarkers that are linked
to resistancegenes.
The
Fhb1
gene, originating from Sumai 3 is one gene which has
been used throughout the world in the development of Fusarium
head blight resistant wheat varieties. Another popular moderately
resistant source used is the Brazilian wheat cultivar, Frontana.
In recent years, a number of novel Asian Fusarium head blight
resistance sources have been characterised and documented,
namely: Asozaira, Baisanyuehuang, Huangcandou, Huangfangzhu,
Haiyanzhong, Ning 7840, YangMai,WanNian 2 andWangshuibai.
Also including CIMMYT derived material, such as CM-82036 and
recently, Catbird. Themajor challenge with these foreign donors is
that they are not adapted toSouthAfrican conditions and a number
of negative effects on yield, quality and other agronomical traits
were reported tobe associatedwith these sources.
There is a need in South Africa for the development of diverse
Fusarium head blight resistant wheat germplasm. A newly funded
Winter Cereal Trust pre-breeding project with this unique need in
mindwas initiatedby theARC inApril 2013.
This pre-breeding programme focuses predominantly on DNA
markers linked toType I andType II Fusariumheadblight resistance
genes/QTLwith stable expression across environments andgenetic
backgrounds. In South Africa there are currently limited Fusarium
head blight resistant wheat cultivars commercially available. This is
compounded by the fact that no fungicide is officially registered for
the control of Fusariumheadblight onwheat.
Theaimof thispre-breedingprogramme is tomakeuseofphenotypic
andmarker-assisted based backcross, to develop diverse Fusarium
head blight and Deoxynivalenol resistant wheat germplasm for the
SouthAfricanwheat industry.
A focused breeding effort is to combine different Fusarium head
blight resistance genes/QTL from multiple Fusarium head blight
resistant donors obtained from the different corners of the world
intoSouthAfricanwheat germplasm.
With a directed focus on the responsible deployment of different
Fusarium head blight resistance gene/QTL combinations to confer
broad and durable resistance against the
Fusarium graminearium
species complex. Ultimately, advanced lineswithdifferent Fusarium
headblight resistancegene/QTLcombinationswhichcanbeused for
moreefficient transfer intoelitebreedingmaterial,will bedeveloped.
Over the last year, this programme has already imported twelve
different Fusariumheadblight resistancedonors for use ina specific
crossing block. These Fusarium head blight resistant donors have
beenvalidatedphenotypically ina field trial nearBethlehem together
withother promising Fusariumheadblight resistant donors.
The resistant donorswereplanted inahill plot designand inoculated
by spray inoculation methods during flowering with a cocktail of
different
Fusarium
isolates. The inoculated heads were covered
by plastic bags to increase humidity (
Photo 3
). The donors were
screenedafter 28days todetermine their resistance levels (
Photo4
).
To further confirm resistance in these donors, a glasshouse trial
by artificial point inoculation method with a cocktail of different
3: An exampleof how each resistant entrywas incubatedwith aplastic bag in the field trial.
3
Reducing the riskof Fusariumheadblight disease
