Old maize and ancient DNA
--Robert Bird, Natasha Bohorova, Diego Gonzalez de León and David Hoisington
CIMMYT's Applied Biotechnology Laboratories have begun a multifaceted project to study the relationships between 600 year old maize from the north coast of Peru and a wide range of traditional races from Peru and elsewhere. ARQUEOBIOS, an organization dedicated to studying archaeological remains of biological materials, associated with the Universidad Nacional de Trujillo, is in charge of coordinating the field work. The ears, kernels and cobs come from habitation and ceremonial sites of the Chimú empire. We plan to use various methods to determine molecular diversity within the ancient maize and to compare this diversity to that in modern maize. The actual methods will depend upon the quantity and quality of the DNA extracted from the ancient embryos. One can predict that no modern maize will prove to be very close to this, but that 8-10-rowed Sabanero Harinoso of the nearby highlands, or Mochero of the same area of the coast will be the closest. According to predictions based on archaeological patterns, the race Cuzco may relate more to Chimú flours than to more geographically proximal races.
A second facet of the study is to see whether there is any sign of life in this ancient material, evidenced by reaction to vital staining, by functioning physiological systems or, just maybe, by cell division. Central to such an effort is the fine-tuning of embryo rescue techniques. We are using as test material some reserve seed from earlier generations of accessions in the CIMMYT Maize Germplasm Bank which has been saved for just such studies. We expect to get revival of at least a significant percentage of seed in samples that have low germination -- certain combinations of nutrients, hormones, light and temperature are promising. Hopefully the results will show that one can retrieve germplasm without resort to tissue culture, an inefficient procedure.
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