Season is a feature that represents the season in which the soybean cultivar is grown. Based on prior knowledge, I can assume the values of this feature range from 1 to 2, with 1 representing one particular season and 2 representing another season.

To analyze the relationship between the Season feature and the grain yield of the soybean cultivar, we need to look at historical data or domain expertise. However, without specific information on the seasons and their impact on grain yield, it is difficult to determine the relationship with certainty.

Given the lack of specific information, I will create a dictionary based on assumptions. Please note that these assumptions are speculative and require actual data or domain expertise to be validated.

```json
{
    "low": [1.1, 1.15, 1.25, 1.3, 1.35],
    "high": [1.9, 1.85, 1.75, 1.7, 1.65]
}
```

In the above dictionary, I have provided five typical values for each target class, 'low' and 'high'. These values represent different seasons within the assumed range of the feature. Again, please note that these values are assumed and should be replaced with actual data or domain knowledge for accurate analysis.