The assessment of the quality of sugar-beet seed

Abstract

SummaryThe accurate prediction of the performance of individual lots of sugar-beet seed in the field is critical when constituting blends of seed for commercial use. Previous studies indicated a need for ‘vigour tests’ to supplement the standard germination test. In many of the studies emphasis was placed on evaluation of tests in the laboratory, whereas in this study equal emphasis was placed on the determination of the values to be predicted. The performance of 20 seed lots with a range of germination between 75 and 95% was assessed in field and laboratory studies in 1981. Further investigations of ten seed lots were made in 1982 and in 1983.The results in 1981 showed little evidence of agronomically important differences in the relative performance of seed lots with respect to establishment in the field at different sites. Similarly, most seed lots showed consistent differences over a range of tests under controlled conditions. However, use of the experiment mean as a measure of stress revealed marked differences in the range of performance between the best and poorest lota in both the field and laboratory. There were clear indications that performance in the field could be modified by non-random factors that tended to reduce the magnitude of differences among seed lots. In 1982 grazing of seedlings by birds was identified as a factor that could cause greater reduction in the establishment of seed lots with high viability relative to those with low viability. Thus, under some circumstances, a single count of seedlings in non-protected field experiments can give misleading estimates of the differences among seed lots (and probably among other treatments which affect the rate of emergence). Correlation coefficients (γ) were about 0·88 for relationships between establishment from pelleted seed in plots protected from birds and germination or emergence under controlled conditions. These results reduced the need for additional vigour tests. However, the studies emphasized that small differences in germination percentage are important as they can be associated with much larger differences in establishment, particularly under adverse seed-bed conditions. The average standard error for the mean viability of individual seed lots was ±1·89 in germination tests with four replicates of 100 seeds at each of six centres. Although inincreased accuracy may not be possible without much greater replication, we found that the distinction between normal and abnormal seedlings was an important source of experimental error. A less subjective measurement, based on hypocotyl height, warrants further study.