Objective

Development of basic knowledge needed to support and expedite production research projects.

Differences in water temperatures within a narrow range - from 14 to 17.6°C (56 to 64°F) -have large effects on panicle sterility. Raising irrigation flood water two to three inches at the "low temperature" stage (Figure 1) helps reduce the panicle sterility, or blanking, problem. High temperatures at flowering time also can cause high sterility. Field studies show wide differences in response of different cultivars to location. Although moderately high rates of nitrogen fertilizers increased sterility, these losses were more than offset by yield increases from other components of yield (more tillers, panicles etc.). Heritability studies on susceptibility to sterility are continuing.

Although environment and stage of maturity at harvest have large effects on head rice yields, a small-seeded mutant (20 percent smaller seeds than Calrose) had higher head rice yields ' than anything else tested.

Physiological studies of carbohydrate formation in rice indicate higher capacity to produce than to store starch in the panicles of late maturing types (Calrose 76 or M7 maturity) while early maturing types appear to be well-balanced.

Production of hybrid rice using male sterile lines gave a 30 percent seed set in 1979, making this method a promising breeding tool. It is highly doubtful that this is enough crossing for commercial production of hybrid seed.

Crosses analyzed for high amylose content revealed that this characteristic is probably under single gene control modified by minor genes.

USDA-UCD studies not funded by the Rice Research Board indicated that certain wild rice species gave stem rot tolerance in crosses with M-101. This work will be accelerated and incorporated into the Rice Research Board project, Transfer of Stem Rot Tolerance from Wild Species of Rice.

 

Figure 1. Comparison of the life cycle of the new early varieties vs. late varieties (cultivars), as charted by UC-USDA scientists M.L. Peterson and J.N. Rutger. As growers adopt the new varieties, this information will enable them to accurately time their water, fertilization, insect and weed control pest management decisions.