Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/25/2008
Publication Date: 3/25/2008
Citation: Chu, Y., Ramos, L., Holbrook Jr, C.C., Ozias-Akins, P. 2007. Frequency of a loss-of-function mutation in Oleoyl-PC Desaturase (ahFAD2A) in the minicore of the U.S. peanut germplasm collection. Crop Science 47:2372-2378. Interpretive Summary: Fatty acid composition is an important characteristic for oil seed crops such as peanut. High oleic fatty acid composition is favored because it confers health benefits and improved oil stability. The high oleic trait in peanut is controlled by two recessive mutations. Peanut has a normal oleic fatty acid composition unless both mutations are present. Plant breeding efficiency would be improved if we could identify the normal oleic peanut genotypes that contained one of the mutations. We developed a molecular marker that can identify those genotypes, and used it to survey the U.S. peanut germplasm collection for the frequency and distribution of the mutated gene. We discovered that almost one-third of the collection contained the mutant gene, and found that this mutation was much more prevalent in some area of the collection, and did not exist in other area. This information will be very useful to plant breeders in making decisions on parents to use in variety development.
Technical Abstract: High oleic acid to linoleic acid ratios (high O/L0 in peanut extend shelf life and provide better nutrition for human consumption. The high O/L trait is controlled by the activity of oleoyl-PC desaturase which is encoded by two genes (ahFAD2A and ahFAD2B) in tetraploid peanut. In a naturally occurring high O/L peanut line F435, the oleoyl-PC desaturase activity is minimal. In this line, a spontaneous mutation (G-to-A transition at position 448 resulting in a D150N amino acid substitution) has been found in ahFAD2A which resulted in a dysfunctional desaturase. The cause for loss-of-function of the ahFAD2B desaturase gene has not been determined. In crosses between normal and high O/L peanut lines, the segregation ratios for high:normal O/L can be either 1:3 or 1:15 suggesting that one of the genes does not encode a functional desaturase in some lines. In order to determine the frequency of the D150N mutant allele in peanut germplasm, we designed a cleaved amplified polymorphic sequence (CAPS) marker to differentiate the mutant and wild-type alleles at the critical point mutation. The CAPS marker was used to screen the minicore collection of the U.S. peanut germplasm collection where the mutant allele was identified in 30% of the accessions. The mutation was confirmed by DNA sequence analysis. Twenty-seven accessions of the putative diploid, A genome progenitor of peanut, Arachis duranensis, contained the wild-type allele. These data suggest that the spontaneous point mutation likely occurred after the polyploidization event that gave rise to autotetraploid peanut. The data also will be useful to breeders who would like to transfer disease resistance traits from minicore members to high oleic acid cultivars.