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June, 2008
Source:
CIMMYT
E-newsletter vol
5 no
6
- June 2008
Centuries ago, Spanish monks brought wheat to Mexico to use in
Roman Catholic religious ceremonies. The genetic heritage of
some of these “sacramental wheats” lives on in farmers’ fields.
CIMMYT researchers have led the way in collecting and
characterizing these first wheats, preserving their biodiversity
and using them as sources of traits like disease resistance and
drought tolerance.
 “I’d
say to Bent: ‘Let’s look for the cemetery,' ” recalls
Julio Huerta,
CIMMYT wheat pathologist, of
his trips to villages in Mexico with his late colleague Bent
Skovmand, CIMMYT wheat genetic resource expert. “And the
sacramental wheats would be there, sometimes hundreds of types.”
The first wheat was brought to Mexico in 1523 around the area
now occupied by Mexico City. The crop soon spread outside the
central plateau with the help of Catholic monks: it traveled to
the state of Michoacán in the 1530s with the Franciscans, while
the Dominicans took wheat to the state of Oaxaca in 1540 and
gave grains to the native inhabitants to produce flour for
unleavened bread used during Roman Catholic religious
ceremonies. “Still today, many church ornaments in Michoacán
have wheat straw in them,” says Huerta.
Huerta and Skovmand went on sacramental wheat-gathering
expeditions in 19 Mexican states. “Many people thought we were
just collecting trash,” he says. “But we wanted to collect
sacramental wheats before they disappeared. I’m not that
surprised that some have very valuable attributes for breeding
programs.”
Farmers in Mexico and elsewhere face water shortages and rising
temperatures due to climate change. CIMMYT scientists are
looking to sacramental wheats as one source of
drought-tolerance. Field trials at the center’s Cuidad Obregón
wheat research facility show some sacramental wheats have better
early ground cover, quickly covering the soil and safeguarding
moisture from evaporating. Others have enhanced levels of
soluble stem carbohydrates which help fill the wheat grain even
under drought, while some show better water uptake in deep soils
thanks to their deep roots.
As farmers gain access to improved varieties or migrate to
cities, sacramental wheats are disappearing from fields. With
the hope of conserving these rare and valuable varieties, Huerta
and Skovmand started collecting them in 1992, collaborating with
the Mexican National Institute for Forestry, Agriculture, and
Livestock Research (INIFAP) and supported by the Mexican
Organization for the Study of Biodiversity (CONABIO). Their
efforts were not in vain—10,000 samples from 249 sites in Mexico
were added to the CIMMYT germplasm bank, and duplicate samples
deposited in the INIFAP germplasm bank.
Only the strongest survive
 The
deep volcanic soils of Los Altos de Mixteca, Oaxaca, and the dry
conditions in some parts of Mexico were not ideal for growing
wheat. “If the wheats didn’t have deep roots and it didn’t rain,
they were dead,” says CIMMYT wheat physiologist,
Matthew Reynolds
(photo). The wheat genotypes that survived for centuries were
perhaps the ones with drought-tolerance traits for which farmers
selected. “Say the farmer had a mixture of sacramental wheats
that looked reasonably similar—similar enough that he could
manage them but diverse enough to adapt to local conditions,”
explains Reynolds. “One year certain lines would do better than
others and the farmer might harvest just the best-looking plants
to sow the next year.”
Sacramental wheats often grew in
isolated rural areas, meaning that some never crossed with other
varieties, leaving their genetic heritage intact. They are often
tall and closely adapted to local conditions, according to
Huerta, and farmers who still grow them say they taste better
than modern varieties.
Reynolds is combining the old and the new—crossing improved
modern cultivars with sacramental wheats to obtain their
drought-tolerance attributes. “We now have several lines that
are candidates for international nurseries,” he says. “They’ll
go to South Asia and North Africa, and will be especially useful
for regions with deep soils and residual moisture.”
Old wheats come back in style
In 2001, a new leaf rust race appeared on Altar 84, the most
widely-grown wheat cultivar in Sonora State, Mexico. The CIMMYT
wheat genetic resources program immediately looked for sources
of resistance in the germplasm bank. The durum collection of
sacramental wheats from Oaxaca, Mexico, proved extremely useful:
all but one displayed minor gene or major gene resistance to the
new leaf rust race, confirming that sacramental wheats are a
valuable breeding resource.
CIMMYT researchers are still unlocking the potential of
sacramental wheats. “We started to characterize them for
resistance to leaf and yellow rust, and the collections from the
state of Mexico for wheat head scab and Septoria,” says Huerta.
We were surprised to find many, many resistant lines. “But until
we finish characterizing all of them, we won’t know what else is
there.” |
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