ALTERATION OF THE OMEGA-3-FATTY-ACID DESATURASE GENE IS ASSOCIATED WITH REDUCED LINOLENIC ACID IN THE A5 SOYBEAN GENOTYPE

Reducing the linolenic acid (18:3(omega 3,6,9)) concentration of soybe an [Glycine max (L.) Merr.] oil may lessen the need for chemical hydro genation and enhance flavor stability. Soybean genotypes A5 and A23 ha ve reduced linolenic acid concentration compared with current cultivar s. Seed linolenic acid is synthesized primarily by the omega-3 fatty a cid desaturase located in the microsomes. The objective of this resear ch was to study whether this enzyme has a role in reducing the fatty a cid levels in the soybean genotypes A5 and A23. DNA from A5 and A23 wa s analyzed by gel-blot hybridization with a cDNA encoding the omega-3 fatty acid desaturase. A5 and lines selected from it have a DNA fragme nt missing compared to A23 and lines with normal linolenic acid concen tration. Seventy F-4:5 lines from a population segregating for linolen ic acid concentration were scored for presence or absence of the fragm ent. The absence of the fragment was significantly (P less than or equ al to 0.0001) associated with a reduced linolenic acid level and accou nted for 67% of the variation for linolenic acid in the population. Th ese results suggest that the reduced linolenic acid concentration in A 5 was at least partially the result of a full or partial deletion of a microsomal omega-3 desaturase gene. No DNA polymorphisms were found f or the desaturase gene in A23, so no mutations could be studied in thi s line.