Four Genes Controlling Root Fluorescence in Soybean1

As part of characterizing genetic diversity in soybean [Glycine max (L.) Merr.] germplasm, 572 accessions were evaluated for root fluorescence when exposed to ultraviolet light. Fifty‐nine accessions did not exhibit root fluorescence. Only two other lines without root fluorescence had been identified previously. Lack of root fluorescence was more common in accessions from Europe (19%) than from Asia (3.4%). Genetic studies of the nonfluorescent accessions showed that four independent genes controlled the absence of root fluorescence. Three were recessive, frl, fr2, and Fr4, and one was dominant, Fr3. Geographical distribution of the four genes was unequal; fr1 was found in accessions from all geographical areas represented, Fr3 and fr4, were found only in accessions from Asia, and fr2 was restricted to accessions from Europe.