Based on prior knowledge, the relationship between the feature 'Repetition' and the target variable 'grain yield of soybean cultivar' can be analyzed as follows:

Since the feature 'Repetition' refers to the number of times an experiment or observation is repeated, it is reasonable to assume that a higher repetition value might result in a more accurate estimation of the grain yield. Therefore, we can expect higher values of 'Repetition' to generally lead to a higher grain yield.

However, it is important to note that the relationship between 'Repetition' and grain yield can be influenced by various factors such as experimental conditions, agricultural practices, and genetic variations among soybean cultivars. Therefore, it is necessary to analyze the data specific to the given soybean cultivar in order to make a more accurate determination.

Based on this analysis, the dictionary with the possible values of 'Repetition' for each target class can be generated as follows:

```json
{
	"low": [1.0, 2.0, 3.0, 4.0, 5.0],
	"high": [5.0, 6.0, 7.0, 8.0, 9.0]
}
```
Please note that the specific values provided above are hypothetical and may not represent actual data. It is recommended to analyze the specific dataset or consult domain experts to obtain more accurate information about the relationship between 'Repetition' and the grain yield of the given soybean cultivar.