sugar beet vs Beta vulgaris

sugar beet and Beta vulgaris both are nouns.

Word	Noun	Adjective	Verb	Adverb
sugar beet	Yes	No	No	No
Beta vulgaris	Yes	No	No	No

As nouns, Beta vulgaris is a hypernym of sugar beet; that is, Beta vulgaris is a word with a broader meaning than sugar beet:

sugar beet: form of the common beet having a sweet white root from which sugar is obtained
Beta vulgaris: biennial Eurasian plant usually having a swollen edible root; widely cultivated as a food crop

Other hypernyms of sugar beet include beet, common beet.

sugar beet (noun)	Beta vulgaris (noun)
white-rooted beet grown as a source of sugar	biennial Eurasian plant usually having a swollen edible root; widely cultivated as a food crop
form of the common beet having a sweet white root from which sugar is obtained