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BIOGENETICS
food Fight
our food secUrity challenge
A team of scientists from Swinburne and the
Royal Botanic Gardens Melbourne are hoping
to unlock the acacia plant’s genetic secrets to
counteract the threat of dryland salination,
the so-called white death.
by julian cribb
An insidious cancer is spreading in
Australia’s productive farmlands and
undermining our food security: the
“white death” of salinity is far from
defeated, and fresh weapons are urgently
needed in the continuing struggle to reclaim our
landscapes from its grip.
At the forefront of that battle is a team of scientists
from Swinburne and the Royal Botanic Gardens
Melbourne: Professor Mrinal Bhave, doctoral
researcher Shanthi Joseph and Dr Daniel Murphy
are convinced the solution to salinity is to be found
in the continent’s ancient gene pool – and are
searching hard to uncover its secrets.
A millenia-old problem
Time and again, as the climate fluctuated, salt has
ebbed and flowed across the arid Australian
landscape – challenging our hardy native
acacias and saltbushes to evolve and adapt
in a subtle genetic guerrilla war waged over
almost 30 million years. The team believes
that in these tough trees and shrubs reside
the secrets of how to withstand and defeat the
encroaching salt.
“Many Australian plants, especially the
saltbushes and acacias, are highly salttolerant
and can grow in conditions which
cause most other vegetation and crops to
die,” Professor Bhave explains. “Over recent
decades there have been some outstanding
practical experiments by farmers and land
managers where salinised land has been
reclaimed by planting them.
“What we still do not know is how these
salt-tolerant species do it. There is a great
and complex biochemical secret within their
genes – and we are trying to work out what
it is. This knowledge, in turn, will lead us to
new species and better methods in the fight
against salt, as well as fresh opportunities in
agriculture and landscape management.”
Threatening our natural
resources
The National Land and Water Resources Audit
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estimates that 5.7 million hectares of Australia are
at high risk from dryland salinity. Without effective
management, this area could stealthily encompass
17 million hectares of good farming country by 2050,
poisoning it in the same way the ancient Romans
poisoned the fields of Carthage by sowing salt.
The risk is not only to food production, but also to
native landscapes and river systems that can turn
hostile to life.
Furthermore, salinity is far from an exclusively
Australian problem. It encompasses an estimated
77 million hectares of country worldwide, affecting
every inhabited continent and several of the world’s
key food-bowl regions – in particular it is killing
areas of vitally needed farmland in India and
Pakistan, sub-Saharan Africa and the Middle East.
It poses a real threat to global food security.
Secondary salinity is primarily a
man-made problem: the clearing
of trees and shrubs for rain-fed
agriculture and the heavy use of water
in irrigation has rapidly brought
underlying salty groundwaters to the
surface, rendering the soil unfit for
food production. The answer lies in
using the best plant species to ‘pump
ACACIA:
a plant of
many talents
The acacia could be
described as a ‘wonder
plant’ – yielding the
following by-products:
High-value timber
for furniture
Charcoal for
energy production
or steelmaking
Fodder for livestock
Biodiesel
Edible and
nutritional seeds
Pharmaceuticals
out’ the groundwater, lowering it to a
safe level.
Studying the acacia’s
evolution
One of Australia’s leading authorities
on acacias, Dr Murphy has been
assembling the ‘family tree’ displaying
the phylogenetic relationships between
Australia’s 1000-plus acacia species.
“This is helping us to understand how
they have evolved over the past 20 to
30 million years, their special
attributes and the connections
between seemingly quite differentlooking
species,” he explains.
Professor Bhave and Shanthi Joseph
are using this collaborative data to
carry out intensive biochemical and
genetic investigations with the aim of
explaining just how incredibly tough plants like our
native saltbushes deal with salt.
“There appear to be several different pathways for
handling salt – some plants take it in and isolate or
excrete it, others may filter it in the roots or exclude
it at the roots,” says Professor Bhave. “One of the
most important aspects is that the ability to deal
with salt also appears to go with the ability to handle
drought, which is of vital concern to the food-growing
industry. So this knowledge has wide relevance.”
Salt-tolerance properties
Using genetic markers and working from four acacia
species known to be salt tolerant, the team has so
far identified around 30 other species of acacia with
similar characteristics, and is preparing to put them
to the ultimate test of seeing how they cope with very
salty conditions, and which ones perform best.
As a bonus, Ms Joseph has demonstrated that
some of the most salt-resistant saltbushes also
produce compounds that may be beneficial to the
health of animals, including sheep, meaning that
productive activities like wool and meat production
can occur on land being reclaimed from salt.
Acacias can yield a wide range of useful byproducts
(see box, left) turning the act of land
reclamation from salt into a range of potentially
profitable new farming and agro-forestry industries
built on a suite of salt-tolerant species that can
cope with different environments. All this depends,
however, on a clearer scientific insight into how
these plants function and what gives them their
special attributes.
This knowledge will not only benefit Australian
farmers and landscape managers – and consumers
too – but in time may help to defuse emerging
salinity crises in many other similarly affected parts
of the world, Professor Bhave says.
Adds Dr Murphy, “Our plants have been evolving
these special attributes for tens of millions of
years, adapting to harsh, dry and saline conditions.
Through this work we are gaining new insights
into the Australian evolutionary story, but also
understandings that will be of real value when it
comes to protecting our landscapes and food supply
into the future.” l
issue three 2012 | venture | swinburne | 7