ARS | Publication request: Two alleles of ahFAD2B control the high oleic acid trait in cultivated peanut

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 20, 2009
Publication Date: January 25, 2010
Citation: Chu, Y., Holbrook Jr, C.C., Ozias-Akins, P. 2009. Two alleles of ahFAD2B control the high oleic acid trait in cultivated peanut. Crop Science. 49:2029-2036.

Interpretive Summary: Oleic and linoleic acids account for 80% of the fatty acids found in peanut oil. The oleic:linoleic acid ration (O/L) in normal peanut genotypes ranges from 1.0 to 4.0, whereas the O/L ratio can reach 35 to 40 in high O/L mutant lines. High O/L is a desirable trait in peanut, and the trait is control primarily by two recessive genes, ahFAD2A and ahFAD2B. The objective of this study was to evaluate the genetic sequences for these mutations and develop molecular marker that can be used in breeding for high O/L varieties. Our data clearly show that molecular markers can be used to screen for known ahFAD2 mutations and that only two mutant ahFAD2B alleles are present in the U.S. high O/L cultivars. Genetic markers based on these mutations have utility for detecting seed mixtures and heterozygotes, and can accelerate introduction of the high O/L trait into peanut breeding lines.

Technical Abstract: A high oleic:linoleic acid ratio (O/L) in peanut (Arachis hypogaea L.) seeds is controlled primarily by two recessive genes, ahFAD2A and ahFAD2B (ol1 and ol2). Marker-assisted breeding for high O/L could become routine provided that user-friendly and economical markers could be developed that would target mutant alleles underlying the trait. Previously, a mutant allele of ahFAD2A was characterized as having a 448G>A transition, and the two ahFAD2B alleles were found with either a nonsense mutation caused by a single nucleotide insertion (441_442insA)(high O/L line F435) or a transposable element insertion (Flavorunner 458). A cleaved amplified polymorphic sequence (CAPS) marker targeting the 441_442insA site in ahFAD2B was designed. ‘Georgia-02C’ and Georgia Hi-O/L’, derivatives of irradiation-induced high O/L mutants, showed CAPS markers and sequence data diagnostic for the genetic mutation in ahFAD2 found in the spontaneous mutant line F435. In addition, conflicting reports regarding the organization of ahFAD2 genes and ahFAD2B mutations were reexamined. Our data clearly show that molecular markers can be used to screen for known ahFAD2 mutations and that only two mutant ahFAD2B alleles are present in the U.S. high O/L cultivars. Genetic markers based on these mutations have utility for detecting seed mixtures and heterozygotes, and can accelerate introduction of the high O/L trait into peanut breeding lines.