Molecular basis of the low linolenic acid trait in soybean EMS mutant line RG10

A possible solution to stability problems is to genetically reduce the content of linolenic acid in soybean seed. RG10 is a low linolenic acid line (< 25 g/kg) produced by ethyl methane sulfonate (EMS) treatment of the low linolenic acid EMS mutant line C1640. The objective of this study was to determine the molecular basis of the low linolenic acid trait in RG10. Sequence analyses of mutant RG10 and wild-type OX948 omega-fatty acid desaturase (Fad3) genes showed that the low level of linolenic acid in RG10 is likely a result of mutations in two Fad3 genes. A mutation in the Fad3A gene introduces a stop codon in exon 6 that would prematurely terminate translation and a second mutation in the 5' splice site of intron 5 of the Fad3B gene may result in abnormal mRNA splicing products. Both mutations would result in a non-functional enzyme. Molecular markers developed for these mutations should simplify and accelerate introgression of the RG10-based low linolenic acid trait into elite soybean cultivars.