isoline

(Isogenic line.) One line in a series of genetically similar plant lines that carry different specific genes for resistance to a particular pathogen.
Found on http://ppathw3.cals.cornell.edu/glossary/Defs_I.htm

Isoline

A line joining points of equal value. Examples of these include height contours on a map or isobars showing atmospheric pressure on a weather map.
Found on http://www.encyclo.co.uk/local/20195

Isoline

Lines on a map joining points of equal value.
Found on http://www.physicalgeography.net/physgeoglos/i.html

isoline

line connecting points on a map having some similar feature
Found on http://phrontistery.info/i.html
No exact match found