Based on my prior knowledge, the feature "Cultivar" can have an impact on the grain yield of soybean cultivars. Different cultivars may have different genetic traits and characteristics that can affect their yield potential.

To analyze the relationship between the "Cultivar" feature and the target variable of grain yield (low or high), we need to identify if there are any consistent patterns or trends in the data.

Let's examine the provided cultivar names and their corresponding grain yield information:

- FTR 3190 IPRO: Unknown
- FTR 4288 IPRO: Unknown
- NK 8770 IPRO: High
- MONSOY M8606I2X: Low
- M 8644 IPRO: Unknown
- ADAPTA LTT 8402 IPRO: Unknown
- 98R30 CE: High
- FORTALEZA IPRO: Unknown
- MONSOY 8330I2X: Unknown
- SUZY IPRO: Unknown
- TMG 22X83I2X: Unknown
- EXPANDE LTT 8301 IPRO: Unknown
- FORTALECE L090183 RR: Unknown
- 83IX84RSF I2X: Unknown
- 82HO111 IPRO - HO COXIM IPRO: Unknown
- 82I78RSF IPRO: Unknown
- SYN2282IPRO: Unknown
- ATAQUE I2X: Unknown
- NK 8100 IPRO: Unknown
- FTR 4280 IPRO: Unknown
- LYNDA IPRO: Unknown
- BRASMAX OLIMPO IPRO: Unknown
- LAT 1330BT: Unknown
- FTR 3179 IPRO: Unknown
- 97Y97 IPRO: High
- BRASMAX BÔNUS IPRO: Unknown
- PAULA IPRO: Unknown
- NEO 790 IPRO: Unknown
- LTT 7901 IPRO: Unknown
- GNS7900 IPRO - AMPLA: Unknown
- 79I81RSF IPRO: Unknown
- ELISA IPRO: Unknown
- NK 7777 IPRO: Unknown
- 77HO111I2X - GUAPORÉ: Unknown
- GNS7700 IPRO: Unknown
- FTR 3868 IPRO: Unknown
- MANU IPRO: Unknown
- NEO 760 CE: Unknown
- 74K75RSF CE: Unknown
- 96R29 IPRO: Unknown

Based on the provided information, we can see that only two cultivars have a clear indication of grain yield: NK 8770 IPRO and 97Y97 IPRO, which have a high grain yield.

Unfortunately, we do not have enough information about the remaining cultivars to determine their grain yield classification. Therefore, I can't provide any specific values for the "low" or "high" classes.

However, I can list the available cultivar names for each class based on the provided information:

```json
{
   "low": ["MONSOY M8606I2X"],
   "high": ["NK 8770 IPRO", "97Y97 IPRO"]
}
}
```

Please note that this analysis is limited by the provided information and may not accurately represent the relationship between the "Cultivar" feature and the grain yield. Additional data and analysis may be required for a more comprehensive understanding.