
Specialty
Bean Tissues No Treat for NematodesBy Jan Suszkiw August 22, 2001Jack beans, sun hemp and coffee senna
aren't your typical, garden-variety beans. But these little-known legumes may
soon find favor among southern farmers and gardeners. Greenhouse studies by
Agricultural Research Service (ARS) and
University of Georgia scientists in Griffin,
Ga., show that mixing dried bean plant material into the soil reduces root-knot
nematode numbers there. In the South, this roundworm species attacks peanuts,
soybeans, corn, cotton, tobacco and other crops, causing yield losses and
control costs of $53 million annually. Farmers strike back with chemicals, crop rotation and resistant cultivars.
But new weapons are always needed. Discing bean material from a cover crop of
the legume prior to planting a high-value crop like cotton may offer farmers
greater flexibility in how they control the pest, notes ARS agronomist Brad
Morris. In tests, mixing dried bean material into potting soils resulted in a 67- to
89-percent reduction in the number of nematode galls on the roots of test
tomato plants versus control plants. Scientists attribute this nematicidal
activity to natural substances produced in the legumes leaves, stems and
seeds. Of 18 legume species tested, Jack bean (Canavalia ensiformis) earned
the highest marks, according to Morris, with ARS
Plant Genetic
Resources Conservation Unit in Griffin. There, he regenerates and
distributes seed from a "special-purposes" legume collection. It
includes 64 genera, or genetic groups, representing hundreds of semitropical
legume species collected from around the world. Most have multiple uses, from
controlling weeds and erosion to providing drug companies with pharmaceutical
compounds. Jack bean, a shrublike plant adapted to southern climates, flowers in July
through August. Though normally grown as a cover crop, the bean plant's seeds
can be eaten if properly boiled. In addition to concanvalin-A, a lectin protein
with many biochemical properties, Jack bean also is a source of the enzyme
urease. Pharmaceutical companies extract both concanvalin-A and urease from the
plant for use in diagnostic tests. ARS is the U.S. Department of
Agriculture's chief scientific research agency. Story contacts Plant Genetic Resources Jan R Suszkiw U.S. Department of Agriculture | |