Fungicides from the soil
Karen du Plessis
Bacillus micro-organisms living in the very soil where crops are grown were put to the
test and proofed to produce ingenious weapons for the effective control of diseases
and mould on fruit.
T
he perishable produce industry
experiences considerable post-harvest
crop losses every year. It is estimated
that between 25% and 40% of the
fruit and vegetables harvested worldwide are
lost to post-harvest diseases. Much of this
is due to decay caused by microorganisms
(fungal, bacterial and viral phytopathogens)
that produce diseases that occur during the
transport, storage and sale of fresh produce. fungicides having been deregistered, certain
pathogenic strains have developed resistance
to the fungicides. Internationally, consumers
are demanding that natural alternative control
methods be found.
Synthetic chemical fungicides that control
post-harvest disease are increasingly
associated with adverse environmental
impacts and health issues, and are therefore
falling out of favour due to the chemical
residues they leave behind in the food chain. Unlocking potential
In a previous Hortgro Science and PHI
Programme-funded research project, Prof.
Kim Clarke, from the Department of Process
Engineering at Stellenbosch University,
identified the potential value of the metabolic
bioproducts of Bacillus amylolique faciens to
be a green fungicide against Botrytis cinerea
in table grapes. She found that her chosen
biocandidate acts as a natural microscopic
factory of lipopeptides that demonstrate the
ability to act as fungicides across a broad
spectrum. She furthermore established that
the bioproducts, even in crude, unpurified
form, are effective in any physical and
chemical environment.
In addition to some of the most effective
Prof. Kim Clarke, project leader.
The search for innovative and acceptable
controls has led the agricultural sector to
green chemistry as a way to manage and
eliminate fungal and bacterial post-harvest
diseases.
Building on her previous work, Prof. Clarke
designed a follow-up project focusing on
pathogens that eat away at the profits of stone
fruit producers.
To upscale the production process from
shake flask (500ml) to the level of a
bioreactor with a capacity of two litres, is a
necessary task.
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