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Compass is a quarterly publication of the USDA Forest Service's Southern Research Station (SRS). As part of the Nation's largest forestry research organization -- USDA Forest Service Research and Development -- SRS serves 13 Southern States and beyond. The Station's 130 scienists work in more than 20 units located across the region at Federal laboratories, universites, and experimental forests.



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Issue 11

Chestnut Cytogenetics: Faridi, Burnham, and McClintock

By Paul Sisco

Cytogenetics, the study of the behavior of chromosomes and their effect on heredity, has a long and distinguished history that includes several winners of the Nobel Prize.

Charles Burnham, one of the founding scientists of The American Chestnut Foundation (TACF) would be very interested in the cytogenetic studies of chestnut that Nurul Faridi has taken on at the SRS Southern Institute of Forest Genetics. Burnham, a distinguished cytogeneticist and generous teacher, trained at Cornell University during the “golden age of maize cytogenetics” in the late 1920s and early 1930s, when research on corn revealed the link between chromosome behavior seen under the microscope and genetic changes seen in corn plants in the field.

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A group of students and postdoctoral research associates which included Burnham, George Beadle, Marcus Rhoades, and Harriet Creighton worked with R.A. Emerson in genetics and Barbara McClintock in botany on the pioneering research that led to the discovery of the chromosomal basis of heredity. Beadle and McClintock went on to become Nobel Laureates.

Before coming to Cornell in 1929, Burnham completed his Ph.D. with Alexander Brink at the University of Wisconsin. Brink and Burnham discovered semisterile maize lines with unusual inheritance patterns. They suspected that the pollen sterility was caused by chromosomal differences, but they had no way of looking at the chromosomes to make sure. At Cornell, McClintock taught Burnham how to stain and visualize chromosomes under a light microscope, and with her help, Burnham was able to prove the hypothesis that he and his professor Brink had made about the maize line.

After his stint at Cornell, Burnham went on to a long and distinguished career at the University of Minnesota, where he helped train generations of maize cytogeneticists, including Ron Phillips, who headed up two scientific reviews of TACF in 1999 and 2006—and who came up with the hypothesis about chestnut chromosome recombination that SRS geneticist Faridi is now investigating.

Just as McClintock helped Burnham and Brink prove their hypothesis, Faridi has come up with good evidence to prove the hypothesis posed by Phillips. Almost 80 years after what was seen as its “golden age,” cytogenetics has once again shown itself to be an extremely useful tool—this time in the effort to restore American chestnut trees to the forests of Eastern North America.

Recommended reading:
Rhoades, M.M. 1984. The early years of maize genetics. Annual Review of Genetics. 18: 1–29.





One type of wildland-urban interface is the isolated interface, where second homes are scattered across remote areas.
Charles Burnham, upper left, was a postdoctoral student in his mid-twenties studying corn cytogenetics when this photo was taken at Cornell University in 1929. Marcus Rhoades, standing next to Burnham, and George Beadle (with dog), were graduate students of Dr. R.A.Emerson (in cap), head of the Cornell Department of Plant Breeding and Genetics. At right is Barbara McClintock, who taught Burnham, Rhoades, and Beadle how to work with chromosomes. McClintock and Beadle both won a Nobel prize in Medicine. (Photo courtesy of Richard Zeyen, University of Minnesota)