Rice Breeding Program-90
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Rice Experiment Station Scientists D. Marlin Brandon, director and agronomistCarl W. Johnson, plant breeder Kent S. McKenzie, plant breeder Shu-Ten Tseng, plant breeder Jeffrey J. Oster, plant pathology |
More than 90 new foreign germplasm lines were introduced through quarantine. These new sources of germplasm will be used for varietal improvement by reducing the risk of genetic vulnerability of existing California rice varieties. Work is also continuing on material generated by mutation breeding and biotechnology techniques.
UC Cooperative Extension evaluated the agronomic performance and adaptability of 118 advanced selections in statewide yield tests (see section on variety trials). Preliminary Yield Tests at RES included 582 entries and check varieties.
Long-grain breeding continues to focus on the development of varieties adapted to California with the cooking characteristics of Southern long grains. An early-maturing, high-yielding long grain, 88-Y-774, with. cooking characteristics similar to `L-202' was released in 1991. More sophisticated cooking tests have also been developed.
Medium-grain breeding continues to incorporate important
agronomic characteristics such as high yield potential, resistance to
lodging and disease, seedling vigor, improved milling yields and resistance
to blanking. An early maturing medium grain, 88-Y-317, is scheduled for
Foundation seed increase and further testing in 1991. Increased emphasis
will be placed on identifying the characteristics necessary for improved
milling yields.
Short-grain breeding efforts are geared toward correcting some of the
deficiencies found in current varieties. Emphasis is on improving yield
potential, resistance to lodging, and grain and milling quality. `S-301', an
intermediate-maturing short grain, has given good experimental and field
yield performance and high milling yields. Foundation seed was available in
1990 and 1991, but `S-301' is grown on only a small acreage. Its performance
in the market is unknown.
A strong effort is being made to improve premium quality rices similar to
M-401 and Japanese premiumquality short grains. However, problems have been
encountered in combining the unique cooking and taste characteristics with
desirable agronomic traits. Over 600 lines were evaluated in 1990 cooking
tests. Koshihikari, a high quality Japanese short-grain variety, lodged
completely in statewide yield tests, S "difficult" breeding challenge to
overcome. Other developments in specialty rices include:
Selection for grain quality-translucency and kernel size, shape and
resistance to breakage-remiins a critical part of the breeding program.
Milling yield tests, physico-chemical tests and micro-cooking tests were
conducted on several thousand lines to select for improved rice quality.
Milling evaluations have been increased in medium and short grains,
including analysis of 15 advanced experimental lines and commercial
varieties over a range of harvest moistures.
Development of long grains suited
for California conditions took another step forward this year with
release of L-203
Efforts to incorporate disease resistance have been slow because sources of
disease resistance have a wide range of undesirable characteristics.
Nonetheless, intensified breeding efforts are required because of the
importance of disease resistance:
Good seedling vigor enhances stand establishment, provides competition with
early weed growth, may reduce severity of seedling diseases, and may permit
the use of deeper water for weed suppression. Breeders continue to evaluate
seedling vigor of foreign germplasm for breeding purposes. A Hungarian
variety, Italica livorno, showed both high levels of seedling vigor and
water mold resistance. Work is under way to incorporate these
characteristics into adapted breeding materials.
An experimental line showing resistance to the rice water weevil did not
perform well agronomically. PI 506230 is tall, lodges severely and is
susceptible to blanking. Further agronomic improvements must be made while
maintaining the high levels of RWW tolerance before this character can be
incorporated into adapted varieties.
The experimental line 88-Y-774 was released this year as `L-203: It is a
smooth, early maturing semidwarf long grain. Days to maturity is similar to
`M-202' and 5-7 days less than L-202. Milling and cooking characteristics
are also similar to L-202. This new variety also shows about a 10 percent
yield advantage over L-202. The area of adaptation appears similar to M-202,
thus permitting long grain production in areas where L-202 would mature too
late.
Foundation seed increase is planned this year for 88-Y-317, a smooth, early
maturing medium grain. Compared to M-202, it shows superior straw strength,
higher and more stable yields, more stable head and milling yields, similar
kernel size, shape and seed weight, similar blanking resistance and cooking
quality similar to the Calrose market type.
A new set of about 10 of the most promising entries will undergo breeder
seed increase this year. Outstanding performers are then in a position for
Foundation seed production in 1992.
Results of a three-year study indicate that nitrogen fertilizer efficiency
is greater in fields treated with Londax® than in those treated with
Basagran® or MCPA. This greater efficiency is attributed to the virtual
elimination of broadleaf and sedge weed competition with Londax®.
Consequently, growers are advised to reduce nitrogen rates by 20 to 30
pounds per acre in those fields where Londax® is used for broadleaf weed
control in water-seeded rice. |