IN SEARCH OF QUALITY-Through the "accelerated aging" process researchers attempt to determine the environmental factors that affect seed quality. Seed grown from these research plots will be compared to those given the AA treatment.

In an attempt to predict these differences, one experiment used the accelerated aging or AA procedure. It places seeds in high-moisture, high-temperature conditions for 20 hours, thus giving them the equivalent of several years of natural aging. The goal was to see if this AA "vigor test" could predict which of the seed lots, all with high standard germination scores, had the greatest potential for field emergence.

The results of the AA tests showed a wide range of germination values, even within the seed lots that emerged well in the field. The test correlated well with seedling vigor down to about the 40 percent emergence level but not below that. For lots with greater than 90 percent germination in the standard test, the AA test could provide additional useful information about seedling vigor.

Seed moisture content

To determine the influence of seed moisture content at harvest on seed quality and vigor, several research plots were harvested at various times throughout September and October and then evaluated. In 1987 the plots were of varieties M-201 and L-202. Similar studies were conducted in .1988 with M-202 and S-201 varieties. The laboratory tests were still in progress at the time this report was written, but the results appear ,to be very similar to those for 1987.

"The results of the AA tests showed a wide range of germination values, even within the seed lots that emerged well in the field."

As expected, head rice percentages dropped with lower moisture content but most of the decrease was at moisture levels below 20 percent. Few differences in seed vigor were noted at various moisture contents, either before or after storage for three months. Standard germination percentages decreased slightly for both varieties at the higher harvest moisture levels-above 27 percent for M-201 and 23 percent for L-202.

The researchers concluded that maximum seed quality is achieved at moisture contents in the range of 22 to 24 percent. Further drying would yield only slight additional improvement in vigor and would increase the risk of mechanical damage during harvesting.

Furthermore, careful attention must be paid to postharvest drying if the seeds are harvested at higher moisture contents. Although the seeds are biologically mature at 22 to 24 percent moisture content, they would be susceptible to rapid deterioration in quality if stored for prolonged periods at these moisture levels.