MASTER BREEDER-Dr. Shu-Ten Tseng, one of three plant breeders at the Experiment Station, has been responsible for much of the time-consuming work of selecting the lines that will lead to improved rice varieties.

• Release to growers of S-101, a very early maturing short grain, and M-203, an early maturing, premium quality medium grain.
• Submission of M-103 for final approval and probable release during 1989. This is a very early, smooth, medium-grain rice similar to M-101 but with more resistance to lodging, blanking and stem rot, as well as a high yield potential.

Meanwhile, the breeding program made 827 new crosses, 350,000 individual panicle selections from the second-generation populations, and more than 80,000 progeny rows (third through seventh generation). Specific breeding targets are yield, cold tolerance, early maturity, lodging and disease resistance, as well as high milling yield and other quality characteristics.

Germplasm sources

To maintain a broad germplasm base for the breeding program, new lines are continually sought from other researchers, from germplasm exchanges and from rice collections. This year new materials from various sources were included in yield tests and introduced as parent lines. In addition, a plant introduction permit was issued to the Rice Experiment Station plant pathologist, which should dramatically improve the introduction of foreign germplasm.

Long-grain quality

A scientific comparison of Southern long-grain rice varieties grown in California and in Texas this year showed no significant difference in cooking quality. This indicates that it may be possible to develop a California longgrain approaching the cooking quality of Southern rice varieties.

The major thrust of the long-grain breeding program is to combine agronomic characteristics needed in California with the cooking quality of Southern long-grain rice. More sophisticated chemical tests of cooking quality are being introduced to facilitate the process.

Two promising, very early maturing experimental long-grain cultivars have been identified for further testing. They have an earlier heading date than L-202, and also show better milling yields.

Medium and short grains

Although the characteristics of agronomic performance-yield, seedling vigor, heading date, and various resistances-remain important targets for the medium- and short-grain breeding programs, efforts have increased to improve milling and cooking quality. Improved versions of new varieties like S-101 and M-103 are in the preliminary testing stage, and results so far look promising. As a result of good performance in the statewide yield tests, several of these short-grain and medium-grain lines are being considered for preliminary seed increase. Meanwhile, the 1989 nursery selections will bring a new wave of genetically diverse lines.

Disease resistance

In their program to build higher levels of plant disease resistance into California rice varieties, especially against stem rot, the plant pathologist and plant breeders:

• Selected promising lines from 96 original crosses made with a wild rice (Oryza rufipogon). One offspring in particular, with good plant type and yield potential, is being used extensively in new crosses as a source of stem rot resistance.
• Grew 36 new plant introductions under quarantine conditions-the first time this process has been allowed.
• Tested several races of the stem rot fungus to see if any might overcome the present sources of resistance. None was found in these preliminary trials.
• Compared a resistant line and four California varieties' in heavily inoculated field tests. The resistant line performed significantly better, not only against stem rot but also against aggregate sheath spot.
• Tested the effect of higher water level on the location of stem rot lesions. Results indicated that raising the water level does not place lesions high enough on the stems to allow a combine to cut below them.

Breeding for quality

Three main quality targets in the breeding program are kernel characteristics, cooking characteristics, and milling yield. The researchers reported that:

• Kernel size, shape, breakage and translucency were the basis of selecting about 60,000 panicles from an original total of 300,000 created by cross-breeding.
• In addition to the special cooking tests on long-grain varieties, tests for premium quality in medium- and short-grain breeding lines were begun in 1988. The most advanced level of cooking quality evaluation is made by California rice marketing organizations and others, using standardized forms. During the year, 14 of the most promising experimental lines were taste-tested in this way.
• Milling yield is controlled by many genetic and environmental factors. Furthermore, good agronomic qualities often don't match with good milling characteristics. The breeders' problem, therefore, is to create a balance between milling and agronomic qualities that maximizes productivity and profitability. Tests were begun during .the year to confirm the correlation between percentage of whole kernel brown rice and whole kernel milled rice (head rice). Milling yield was determined on more than 2,400 long-grain samples.

Other activities

The plant breeders also:

• Conducted incubator screening tests to evaluate sources of greater seedling vigor.
• Continued efforts to develop rice water weevil tolerance.
• Continued a small breeding effort for specialty rices.