
Technology Spurs Alfalfa Genome MappingBy Jan Suszkiw August 2, 1999Using computer technology to magnify
light microscope images, scientists are getting the closest look yet at the
chromosome housing for alfalfas genes. The advance opens the door to genome mapping of alfalfas 32
chromosomes for traits like winter hardiness, stand persistence, and resistance
to pests like potato leaf hoppers. Alfalfa is among Americas most widely grown crops, generating over $6
billion annually, primarily as hay. Yet compared to corn or soybeans, less is
known about its complex genetic make-up, slowing breeding efforts. Over the
past 30 years, for example, alfalfas average yield has only increased by
about one percent. Part of the problem also stems from the fact that alfalfa plants are
autotetraploid, meaning their traits are governed by genes residing on
four chromosomes instead of two. The legumes chromosomes are also
hard to distinguish, and barely visible under a microscope. Or so it was until scientists Gary Bauchan and Azhar Hossain tackled the
problem. With help from a Maryland firm, Loats Associates, they attached a
light microscope to a computer imaging system at their Beltsville, Md.,
Soybean and
Alfalfa Research Lab, operated by the Agricultural Research Service,
USDAs chief scientific agency. The result: a 10,000-fold increase in magnification, use of false-color, and
the precise identification and measurement of the chromosomes length--key
to karyotyping, or arranging them from largest to smallest. Along the chromosomes arms, scientists observed thick
bands of heterochromatin, material composed of DNA and protein. Like
chromosomal roadblocks, the bands can impede the exchange of genes during
breeding. One hope is that falcata alfalfas, which contain relatively few
heterochromatin bands, will help breeders introduce new traits from wild
species to domestic cultivars, broadening their genetic base. A longer story about the advance appears in this months issue of
Agricultural
Research, an ARS publication also on the Web at: http://www.ars.usda.gov/is/AR/archive/aug99/gene0899.htm Scientific contact: Gary
Bauchan, ARS Soybean and Alfalfa Research Laboratory, Beltsville, Md.,
phone (301) 504-6649, fax (301) 504-5169,
[email protected]. Story contacts Gary R Bauchan Jan R Suszkiw U.S. Department of Agriculture | |