[Aztlan] Of Chocolate and Easter Bunnies

[Bruce Rogers]

Listeros,

Bad news for the Easter Bunny . . .
It's chocolate egg/bunny season once more and the 
Easter Bunny is worried because chocolate trees 
are increasing under threat.  Chocolate is made 
from the fermented and roasted seeds of the cacao 
tree, Theobroma cacao (Linnaeus, 1753). The cacao 
swollen shoot virus (CSSV) can kill the trees, 
and threatens to slash this year's spring crop by 
a third in the world's biggest producer, Côte 
d'Ivoire  (Ivory Coast) in Africa.  In Brazil, 
Witches' Broom [Moniliophthora perniciosa 
({Stahel} Aime & Phillips-Mora, 2005)] fungus is 
also threatening their cacao crop.

Cheers (nervously),
Bruce Rogers, earth scientist & cacaologist on any old day
++++++++++++++++++++++++++++++++++++++++++++++++++++

Chocolate eggs under growing threat from witches' broom

07 April 2009  by  Debora MacKenzie, New Scientist Magazine issue 2703.

IT'S chocolate egg season again, and sales of the 
pagan and Christian symbols of rebirth are as 
strong as ever. But the hunt for Easter eggs may 
truly be on next year, because chocolate trees 
are in increasing trouble.

Chocolate is made from the fermented, roasted 
seeds of the cacao tree. The cacao swollen shoot 
virus (CSSV) can kill the trees, and threatens to 
slash this year's spring crop by a third in the 
world's biggest producer, Ivory Coast. Meanwhile 
a fungus called witches' broom is doing the same 
in Brazil. Now researchers are racing to sequence 
the cacao genome and find genes that can resist 
CSSV.

Cacao trees are native to the Amazon rain forest, 
but west Africa produces 70 per cent of the 
world's cocoa, virtually all on tiny, 
impoverished farms. In recent years, demand for 
chocolate has mushroomed. The farmers cannot 
afford expensive fertilizer so they boost 
production by planting more cacao trees over a 
greater area. That means cutting down other trees 
that normally grow between cacao crops, which 
also replicate their rain forest origins and give 
them the protective shade they prefer.

"Increasingly cacao is grown almost as a 
monoculture," says Paul Hadley of the University 
of Reading, UK. That promotes the spread of 
disease, as does the trend towards growing the 
trees in drier regions - water-stressed cacao 
trees are less able to fight off disease.

In recent years, CSSV has become an increasingly 
serious problem in Ivory Coast. The virus 
originated in native African trees, in which it 
is endemic, and is spread by common mealy bugs, 
so it can't be avoided. The only defence until 
now has been to destroy millions of infected 
cacao trees to create disease fire walls. Yaw 
Adu-Ampomah and colleagues at the Cacao Research 
Institute of Ghana (CRIG) have found cacao 
varieties in Africa that partially resist the 
killer virus, and they are trying to breed more 
resistant strains.

But progress is slow. New genetic stock brought 
over from South America must be quarantined for 
two years before going to Africa, and 
experimental crosses take three years to grow 
before researchers can test for CSSV resistance.

Ray Schnell and colleagues at the US Department 
of Agriculture lab in Miami, Florida, are trying 
to speed things up. "We're mapping genes for 
resistance to CSSV now," he says. "It will all be 
a lot easier in a few years when we've sequenced 
the cacao genome."

If they can link particular DNA sequences with 
CSSV resistance, they hope to use them to make a 
testing kit so researchers in Africa can screen 
experimental crosses and plant only resistant 
seedlings. The CRIG is already using such a test 
to combat a fungal cacao disease called black pod.

<http://www.newscientist.com/article/mg20227033.500-chocolate-eggs-under-growing-threat-from-witches-broom.html>