Low-temperature tolerance of pepper at germination stage and its evaluation method

108 pepper cultivars were used to evaluate low-temperature tolerance at germination stage based on relative germination potential, relative germination percentage, relative germination index, relative radicle length and relative vigor index at 18 °C. The results indicate that the degree of tolerance varies among pepper cultivars, with significant differences (P<0.05) in relative germination percent, relative germination index, relative radicle length and relative vigor index. Based on the 4 indices, the evaluation score for each pepper cultivar is calculated by pole-sorting method. Using the evaluation scores, 108 pepper cultivars are classified into three categories. Whereas 10 cultivars are low-temperature tolerant, 9 cultivars are low-temperature sensitive and the rest cultivars are moderately low-temperature sensitive. The relative germination potential and relative radicle length of different pepper cultivars exhibit significantly correlation with the evaluation scores. The correlation among relative germination percent, relative germination index, relative vigor index and the evaluation scores is extremely significant. The relative vigor index and the evaluation scores exhibit the highest correlation (r=0.899 9). The results indicate that pole-sorting analysis is an effective method for preliminary evaluation of low-temperature tolerance of pepper in terms of relevant characteristics at germination stage.