To analyze the relationship between the "Cultivar" feature and the target variable ("grain yield"), we need to consider the information provided for each Cultivar. However, without any additional information or data about the relationship between Cultivar names and grain yield, it is not possible to make a definitive analysis solely based on the provided information.

To create the dictionary with the requested format, we can associate all the Cultivar names with the respective target class, "low" or "high". Since we don't have information about which Cultivar names correspond to low or high grain yield, we will simply include all the names in each list. The analysis conducted here is based solely on the information provided.

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

Please note that this analysis is based solely on the information provided and does not take into account any external factors or additional data that might inform the relationship between Cultivar names and grain yield.