Molecular Mechanism And Genetic Enhancement Technology For High Oleic Acid In Peanut (arachis Hypogaea L.)

Peanut (Arachis hypogaea L.) is widely used as an oilseed and cash crop around the world and as a source of edible oil and protein in the developing countries. Properties of peanut oil are determined by the fatty acid composition. Increasing the oleic acid content in peanut seed and its products has been one of the most important goals for improving the peanut quality. Based on investigating of the fatty acid accumulation pattern in developing seeds and the molecular mechanism of high oleic acid, it would be of important value to establish a cost-effective system for gegentic improvement of high oleic acid in peanut.Comparison of fatty acid accumulation pattern in seed development of the high oleic and normal oleic acid peanut genotypes revealed that oleic acid accumulated during the latter seed development stage while more linolenic acid appeared in the early developing stage. Higher palmitic and linoleic acid was found in the embryo of the matured peanut seeds than in the cotyledon. During the germination of the high oleic acid genotype, there was no significant change of the fatty acid, which implied that high oleic character did not affect the seed germination.The inheritance of the high oleic content was reconfirmed by the F2 segerating progenies of normal and high oleic acid cross combinations. Two main-effects with recessive-linked-additional genes plus additional poly-minor-effect gene were found to determine the oleic acid content in the peanut seeds. We characterized two homeologous genes that directly control oleic acid content in the oil, ahFAD2A, ahFAD2B, and these two genes have two alleles (ahFAD2A-wt ahFAD2A-m; ahFAD2B-wt, ahFAD2B-m) in various peanut germplasm accessions. We further confirmed that there was only ahFAD2B-wt allele and no ahFAD2B-m in the Chinese germplasm collection. At the same time, ahFAD2A-wt and ahFAD2A-m were found in the most accessions in the Chinese mini-core collection, the mutant allele ahFAD2A-m was frequent among subspecies hypogaea accessions but absent from subspecies fastigiata accessions. A highly positive correlation between present of the ahFAD2A-m and the higher oleic acid content was observed.A cost-effective refractive index (RI) method was developed to identify the high oleic acid materials, which is useful for high oleic breeding in peanut. Based on the understanding of the molecular mechanism of high oleic acid character, a new system for the high oleic in peanut was developed. The parental lines in breeding should be genotyped to estimate the ratio of the high oleic acid in the F2 population. An easy method using RI was established to identify high oleic phenotypes among F2:3 lines with two recessive genes (ol1ol1ol2ol2).