Based on the feature description and the task, we need to analyze the relationship between the cultivar and the grain yield of soybeans. To do this, we can examine the patterns in the provided data and classify the cultivars into two groups: low yield and high yield.

Here is the analysis:

For low grain yield:
- "NEO 760 CE"
- "MANU IPRO"
- "77HO111I2X - GUAPORÉ"
- "NK 7777 IPRO"
- "97Y97 IPRO"
- "BRASMAX BÔNUS IPRO"
- "LYNDA IPRO"
- "FTR 4280 IPRO"
- "GNS7700 IPRO"
- "ELISA IPRO"
- "79I81RSF IPRO"
- "NEO 790 IPRO"
- "PAULA IPRO"
- "FTR 3179 IPRO"
- "FTR 3868 IPRO"
- "74K75RSF CE"
- "96R29 IPRO"

For high grain yield:
- "77HO111I2X - GUAPORÉ"
- "NK 7777 IPRO"
- "BRASMAX BÔNUS IPRO"
- "97Y97 IPRO"
- "BRASMAX OLIMPO IPRO"
- "NK 8100 IPRO"
- "82HO111 IPRO - HO COXIM IPRO"
- "83IX84RSF I2X"
- "98R30 CE"
- "FORTALEZA IPRO"
- "MONSOY 8330I2X"
- "TMG 22X83I2X"
- "EXPANDE LTT 8301 IPRO"
- "FORTALECE L090183 RR"
- "LAT 1330BT"
- "ATAQUE I2X"
- "SYN2282IPRO"
- "82I78RSF IPRO"
- "M 8644 IPRO"
- "NK 8770 IPRO"
- "FTR 4288 IPRO"
- "FTR 3190 IPRO"

Based on this analysis, the dictionary for the relationship between cultivar and grain yield will look as follows:

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

Please note that this analysis is based on the provided data and may not be applicable to other datasets or scenarios.