Genetic type T218M was found in the cultivar 'Illini' in 1952 at Urbana, Illinois. Genetic type T225M was found in the cultivar 'Lincoln' in Iowa before 1955. T218M phenotypically is similar to T225M in that an unstable allele results in a chlorophyll chimera.
Palmer, Reid G.
"Research Notes : United States : Inheritance and derivation of T218H,"
Soybean Genetics Newsletter: Vol. 14
, Article 44.
Available at: https://lib.dr.iastate.edu/soybeangenetics/vol14/iss1/44