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Junie 2018
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Improved germplasm
can lead to a
brighter
farm future
S
cab/Fusarium head blight is one of the most important
small grain diseases in the world. In South Africa, out
breaks are becoming more severe and frequent due to the
changing climate that mediates the development of optimal
micro-environmental conditions, which facilitate infection.
In addition, maize/wheat cropping systems, planting of susceptible
cultivars and the expansion of irrigation areas favour the spread of
Fusarium head blight. Currently there are no fungicides officially
registered to control this disease in South Africa and this compli
cates the control of this disease.
Stubble from no-till may also harbour
Fusarium
inoculum and
this might become a problem when conditions are conducive to
infections. It must also be noted that in the world, there are
two
Fusarium
species which have displayed chemical resis-
tance already.
During a recent conference in Brazil, concern was raised during
fungicide testing research conducted by different groups over
several years, that fungicides of the strobilurin group significant
ly increase DON mycotoxin levels (6% to 18%) in the harvested
grain after treatment. In addition, researchers have also found that
BT-maize could host
Fusarium
spores for longer periods of time,
since the stubble will take longer to degrade or decompose.
Severe yield losses (0,5 t/ha to 2 t/ha) may occur depending on
the timing of infection and presence of optimal micro-environmen
tal conditions at flowering stage. Infected grain may also contain
mycotoxins that are harmful to both humans and animals.
Since there are currently no local resistant cultivars available and
no fungicides registered to control scab on wheat, a Winter Cereal
Trust project was initiated to improve the Fusarium head blight
resistance levels of our current susceptible South African cultivars.
This project combines the use of phenotypic field screening and
marker-assisted selection to develop diverse scab and mycotoxin
resistant germplasm. DON is one of the most important and preva
lent mycotoxins that might accumulate in the seed after
Fusarium
infection, which has recently received more interest.
The reason why mycotoxins are important is the health issues as
sociated therewith (such as cancer causing/inducing) if ingested
for a prolonged period. As these mycotoxins are harmful, there
are now new regulations in place, which allow a maximum limit in
cereal grains (of ≤ 2 000 μg/kg DON) and derived processed pro-
ducts (such as flour, meal, semolina and breakfast flakes etc of
≤ 1 000 μg/kg DON) meant for direct human consumption.
Mycotoxins are also very important to the barley industry, as these
mycotoxins may lead to gushing of the beer. So, both the wheat and
barley industries have identified Fusarium head blight/scab manage
ment as a national research and development priority.
The question now is how the Fusarium head blight resistance of
our local cultivars can be improved to prevent an imminent disas
ter? Since we know that our local cultivars are not resistant, it is of
utmost importance to import resistant donor lines and/or cultivars
that have known stable Fusarium head blight resistance QTL/genes
from different parts of the world.
In this study, it has become imperative to import well-documented
and characterised
Fusarium
resistant wheat lines that are known to
have different types of resistance. Resistance is categorised into five
specific types (
Table 1
) in which we are interested, to incorporate
into local germplasm.
on farm level
Fusarium head blight / Resistance
Integrated pest control
Cathy de Villiers, Dr Scott Sydenham
and
Nyiko Baloyi,
ARC-Small Grain, Bethlehem
1: Entries tested in the field annually at ARC-Small Grain under supplementary irrigation.
1