March 2, 2001
A test that helps select
disease-resistant sugarcane cultivars more accurately and efficiently has been
developed by Agricultural Research
Service scientists at the agencys
Sugarcane Field Station
in Canal Point, Fla.
The new test screens sugarcane plants for resistance to ratoon stunting
disease (RSD), which causes higher sugarcane losses worldwide than any other
disease--up to 30 percent in some areas. In Florida, RSD causes $36 million a
year in losses. As the name implies, RSD produces stunting and poor growth of
the shoots, or ratoons, that spring up from sugarcane roots.
The new test relies on a serologicalor immune-typeresponse in
the plant. When the plant has been infected by the RSD pathogen, Clavibacter
xyli subsp. xyli, proteins called antigens in the pathogen bind to
antibodies in the test kit, thus giving a positive reading.
To try to eliminate the pathogen from seedcane, growers in many countries
resort to heat- treatment programs. This involves immersing seedcane in water
at a temperature of 122 degrees Fahrenheit before planting, to kill the
bacterium. But heat therapy is expensive and very labor-intensive. It also
doesnt guarantee that RSD-susceptible cultivars wont become
infected in sugarcane fields, because the pathogen is easily transmitted by
contaminated harvesting equipment.
After more than 10 years of screening sugarcane cultivars for genetic
resistance to RSD and conducting field tests, ARS researchers have found that
RSD incidence is significantly lower in cultivars produced by the Canal Point
screening program. One cultivar in particular--CP 72-2086--has proven to be an
exceptional performer. Surveys indicate that RSD incidence in this cultivar has
averaged less than 3 percent per field. In comparison, more than 69 percent of
varieties not selected for their RSD resistance but grown under similar
conditions were infected with RSD.
More than 17 percent of commercial sugarcane acreage in Florida is planted
to this ARS-developed cultivar. It has been RSD-free for more than a decade
without ever being heat treated.
ARS is the U.S. Department of
Agricultures chief scientific research agency.
Scientific contact: Jack C. Comstock, ARS Sugarcane Field Station,
Canal Point, Fla., phone (561) 924-5227, fax (561) 924-6109,