Augustus 2014
92
ON FARM LEVEL
Pest control
About 4%of breeding lineswerepostulated
to carry the Matlabas gene in screening
tests in 2013.
Where didwe get theUg99
variants from?
Rust spores arewind-borne; they are carried
longdistances bywind. In addition, they can
be transported from one place to another
accidentally by sticking to the clothes and
shoes of people. In many cases, new races
can develop locally from existing races
through genetic mutation. Initially, genetic
studies indicated that 2SA88, 2SA106 and
2SA107were exotic introductions intoSouth
Africa (Visser
et al
., 2011).
Some of these races were reported in east
and southern African countries suggesting
that they were probably introduced into
SouthAfrica from thesecountries. Consider
for examplecountries close toSouthAfrica:
2SA88, 2SA88+ and 2SA107were reported
in Zimbabwe and 2SA107 was detected
in Mozambique (
Figure 2
). Spores of
these Ug99 variants could easily be trans-
ported into South Africa by wind and/or
other mechanisms from nearby countries.
Current evidence from more advanced
Figure 1: Distributionof Ug99 variants in themajorwheat growing areas of SouthAfrica.
Figure 2:Occurrenceof Ug99 variants inSouthernAfrican countries.
Variants of stem rust raceUg99 detected inSouthAfrica
