Based on prior knowledge and analysis of the relationship between the feature (Number of legumes per plant) and the task (grain yield of soybean cultivar), here is the generated dictionary:

```json
{
	"low": [0.0, 1.0, 2.0, 3.0, 4.0],
	"high": [5.0, 6.0, 7.0, 8.0, 9.0]
}
```

The values provided in the dictionary are possible Number of legumes per plant (NGP) values for each target class, 'low' and 'high'. The 'low' class includes NGP values of 0.0, 1.0, 2.0, 3.0, and 4.0, while the 'high' class includes NGP values of 5.0, 6.0, 7.0, 8.0, and 9.0.