Based on prior knowledge, the Thousand seed weight (MHG) can be an important factor in determining the grain yield of soybean cultivars. Higher seed weight typically leads to higher grain yield.

To analyze the relationship between MHG and grain yield, we can consider the following:

1. Low Yield: For soybean cultivars with low grain yield, the MHG values may typically fall within a lower range. These lower values indicate smaller seed weights, suggesting lower potential for grain production.

2. High Yield: Conversely, soybean cultivars with high grain yield may exhibit MHG values within a higher range. These higher values indicate larger seed weights, suggesting higher potential for grain production.

Based on these considerations, we can create a dictionary with the requested format:

```json
{
	"low": [0.2, 0.3, 0.15, 0.25, 0.18],
	"high": [0.5, 0.6, 0.4, 0.55, 0.48]
}
```

Note: The values listed above are arbitrary examples and should not be considered as actual values for the MHG feature. The actual values should be determined based on domain knowledge or specific data analysis performed on the dataset.