Seems like a bit of jargon we could do without. Whoever first coined it was not thinking very clearly. What could it possibly mean? (compare with cultivar).

Sounds simalar to the term "Biotype" used in microbiology .. two organisms that differ in general by some small variance .. "biovar" sounds like an shortened version of the terms "bio variant".

I would think one could call a "cultivar" a bio variant or biotype or biovar of some other plant but in microbiology there is ofcourse little or no gross morphology or obvious structures to tell organisms apart such as leaves .. or obvious colors .. two bacteria may only differ in the presence of a single protein found on their cell surface and this small difference would more fittingly called a "biotype" or described as a bio variant or in brief a "biovar".

If you had let's say a new cultivar of poison ivy that was not poisonus anymore because it lacked a skin irratating toxin that would be a good case for using the term "biotype" or bio variant or in short form "biovar".

Given two cultivars with obvious differences in gross anatomy the terms above would not be as appropiate but maybe could be used very loosely.

I'm not a dictionary but that's my two cents.

Good Day ..