Based on the given feature description and task, the feature "MHG" represents the thousand seed weight of a soybean cultivar, measured in grams. The task is to determine the grain yield of the soybean cultivar, categorizing it as either low or high.

To analyze the relationship between the feature "MHG" and the target variable (grain yield), we can use our prior knowledge of soybean cultivation. Generally, higher thousand seed weights are associated with larger and healthier seeds, which can potentially contribute to a higher grain yield. On the other hand, cultivars with lower thousand seed weights may have smaller and less productive seeds, resulting in a lower grain yield.

To create the dictionary, we need to include typical MHG values for each target class ('low' and 'high'). Here is the requested dictionary:

```json
{
	"low": [12.3, 10.5, 11.8, 9.7, 9.2],
	"high": [16.7, 15.1, 17.2, 15.8, 14.4]
}
```

Please note that the values provided in the dictionary are just examples and should be adjusted based on domain knowledge and specific data analysis.