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Rice Researchers Fight Straighthead Disease and Improve
By Jim Core
October 28, 2005
Rice breeding lines that resist a
costly disease, as well as lines with desirable grain characteristics, have
been identified by Agricultural Research Service (ARS) scientists in Arkansas.
Yan, a research geneticist at the ARS
Bumpers National Rice Research Center in Stuttgart, Ark., leads efforts to
analyze the U.S. Department of Agriculture (USDA) Rice Core Collection. With
1,791 entries, this genebank has been estimated to contain more than 70 percent
of the genetic variation in the
Grains Collection's 18,408 rice accessions.
Utilizing the core collection, Yan and his ARS colleagues identified
germplasm accessions that are very resistant, or even immune, to straighthead,
a plant disease that causes the entire rice head to remain upright at maturity
with sterile florets and reduced grain yield.
There is no straighthead resistance in commercial U.S. rice cultivars, but
Yan has identified 26 indica and japonica rice lines that are resistant.
Breeders at the University of Arkansas
and Louisiana State University have
incorporated some of these germplasm lines into their programs.
Straighthead yield losses can reach almost 100 percent if a highly
susceptible variety is planted in the wrong conditions. The germplasm recently
discovered to be resistant is diverse in origin, maturity and plant height.
According to Yan, it can be used to improve straighthead resistance in rice
breeding in the southern United States.
Stuttgart researchers are also addressing undesirable amylose content levels
in indica rice. Amylose content is the characteristic used to describe the
difference between dry, flaky rice (which indicates a high amylose content,
typical for U.S. long grain rice) and moist, sticky rice (which indicates a low
amylose content, typical for U.S. medium grain rice).
Germplasm of foreign indica rice, the principal type grown worldwide,
usually has higher grain yields than U.S. cultivars. However, it is considered
to have poorer grain quality.
Through hybridization and induced mutation breeding,
Rutger, a lead ARS scientist in Stuttgart, and Yan have developed numerous
indica lines with ideal amylose content for the U.S. rice industry.
ARS is the USDA's chief in-house
scientific research agency.