www.checkbiotech.org ; www.raupp.info ; www.czu.cz

CIMMYT?s biometrics team receives special recognition for advancing the
science behind crop genetic resource conservation, February 2006.

The nightmare of a gene bank curator: You have a collection of 25,000
precious, unique samples of maize seed; one of the world?s most extensive.
You store it carefully, keep it cold and dry, but?little by little over the
years?the seed dies! Eventually you?re left with so many packets of useless
kernels, and the precious genetic diversity they once embodied is lost to
humanity forever.

To keep this very bad dream from becoming a reality, Suketoshi Taba, head of
maize genetic resources at CIMMYT, and his team constantly monitor the
germination capacity of collections. When it drops below 80-85%, they take
viable seed from the endangered accession (the term for individual,
registered samples in the bank), sow it under controlled conditions, and
harvest enough from progeny to replenish the accession. Known as
?regeneration,? the process sounds simple, but in fact must be done
painstakingly to capture a faithful snapshot?rather than a faded copy?of the
genetic diversity from the original accession.

The Crop Science Society of America recently bestowed the honor of ?2004
Outstanding Paper on Plant Genetic Resources? on an article by CIMMYT
biometricians that provides models for proper handling of repeated cycles of
regeneration. Their work, which was funded by the Australian Grains Research
and Development Corporation (GRDC), is particularly relevant for
outcrossing, genetically diverse crops like maize, legumes, or sorghum, to
name just a few.

?For maize regeneration, we use artificial pollination, to avoid
out-crossing with pollen from other maize fields,? says Taba. ?But even the
individuals in a maize population or accession are genetically diverse. How
can we decide on the best way to pollinate the plants, or how many ears we
need to harvest, or how many and which seeds to choose from each ear??
According to Taba, the danger is ending up with a sample that differs from
the genetic make-up of the original. And with each successive cycle of
regeneration, you can drift further and further.

Building on a strong body of work in this area by CIMMYT biometricians since
the 1980s, the award-winning paper refines and expands the statistical model
and provides reliable computer simulations. ?Among other things, the
simulation model shows exactly how many alleles are likely to be lost
through various sampling and regeneration strategies,? says Jiankang Wang,
CIMMYT biometrician who is first author of the study. ?It describes how
different strategies can affect the conservation of alleles and gives gene
bank curators options that can be tailored for specific types of
accessions.?

Jiankang Wang says he and his co-author, CIMMYT biometrician José Crossa,
are now working with Taba to apply the paper?s model in managing CIMMYT?s
maize gene bank collection. ?Many other gene banks will find this approach
useful,? says Crossa, explaining why their study received the award. ?For
example, we collaborate closely with the National Center for Genetic
Resources Preservation in Fort Collins, Colorado, in the USA. They can apply
the same principles in their regeneration work.?

Jiankang Wang was excited by the recognition and the fact that peers might
find his work useful. ?In middle school, teachers saw I had talent and told
me to specialize in mathematics, but at the university I discovered that I
was most interested in the practical applications of mathematics,? says
Jiankang Wang. ?Using science to help preserve the world?s crop genetic
resources is a great satisfaction.?

[www.cimmyt.org]

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