Principles of Plant Genetics and Breeding

502 CHAPTER 29
Introduction
The US Department of Agriculture-Agricultural Research Service (USDA-ARS) rice breeding program located at the Texas A&M
Research and Extension Center at Beaumont has been in operation since the early 1930s. The objective of this program has been
to develop superior performing rice cultivars that are adapted to the southern rice growing region of the United States, which
includes Texas, Louisiana, Arkansas, Mississippi, and Missouri. Some 80% of this region is dedicated to the production of long
grain cultivars, while 20% produces medium grain cultivars, with a small percentage dedicated to specialty rice cultivars for
niche markets. In the USA, the conventional market classes of rice are categorized according to grain dimensions and cooking
quality, the latter being primarily determined by amylose content and starch gelatinization temperature (Webb 1985). The development
of new rice cultivars must include selection for agronomic traits, resistance to disease and insect pests, and grain quality
traits (McClung 2002). In addition, cultivars that are produced along the Gulf coast of Texas and Louisiana, where the growing
season is relatively long, are also evaluated for second crop potential, which is called the ratoon crop. After the main crop is harvested,
a second crop develops from the stubble of the first crop. About 60 days after the main crop harvest, the ratoon crop is cut,
producing up to 50% of the first crop’s yield.
Most public rice breeding programs use standard pedigree, bulk, and backcross breeding approaches. However, mutation
breeding and recurrent selection methods are also used to a limited extent. Many of these programs are now using molecular
markers that are associated with traits of economic importance to expedite the breeding process. In addition, there are private
breeding programs that are developing rice hybrids and others that are using transgenic technology (McClung 2004).
The development of “Saber” rice (McClung et al. 2004) is an example of a recent breeding project conducted by the Beaumont
Rice Variety Development Program. In 1989, a cross was made between “Gulfmont” and an experimental selection, RU8703196.
At the time, “Gulfmont” was a new release from the breeding program that was characterized as an early maturing, semidwarf,
long grain cultivar having excellent main and ratoon crop yield as well as good milling quality. It is rated moderately resistant to
blast disease (caused by Pyricularia grisea) and very susceptible to sheath blight disease (caused by Rhizoctonia solani) (Bollich
et al. 1990), the two most common yield-limiting diseases in the southern rice growing region. RU8703196 is a long grain
germplasm source that was released as an improved source of resistance to blast and sheath blight diseases (Marchetti et al.
1995). The F 1 of “Gulfmont”/RU8703196 was then crossed with “TeQing” (PI 536047). This is a medium grain cultivar from
China that is characterized as having high yield potential, intermediate height, relatively late maturity, and excellent resistance to
blast and sheath blight diseases when grown in the southern US. The objective of the cross was to maintain the plant stature and
grain quality of “Gulfmont” while improving its yield and disease resistance.
Timeline for the development of “Saber” rice
1989
Make cross B8910 (“Gulfmont”/RU8703196//“TeQing”) in the greenhouse and produce 27 F 1 seed (Figure 1). Plant each F 1 seed
in separate containers in the greenhouse. Harvest F 2 seed from each F 1 plant separately.
Plant bulk of each F 1 -derived F 2 population in the fall planted nursery in Puerto Rico. Three of the F 1 -derived populations
appear to be selfs and are discarded. Strip bulk of F 3 seed from F 2 plants at harvest.
1990
Plant bulk of F 1 -derived F 3 populations in the winter planted nursery in Puerto Rico. Strip bulk of F 4 seed from F 3 plants.
Plant bulk of F 1 -derived F 4 populations in summer nursery in Beaumont, TX. Strip bulk of F 5 seed from F 4 plants.
1991
Anna Myers McClung
Industry highlights
Breeding rice
USDA-ARS Dale Bumpers National Rice Research Center and Beaumont Rice Research Unit, 1509 Aggie Drive, Beaumont,
TX 77713, USA
Plant bulk of F 5 population in the summer nursery. Select panicles from a total of 215 plants for the B8910 project based upon
field observations of plant height, days to heading, good tillering capacity, and good appearing grain dimensions.