Genetic And Molecular Marker Research Of Oleic/Linoleic (O/L) Ratio In Peanut

Peanut (Arachis hypogaea L.) is an important oil crop worldwide andthe oleic/linoleic ratio is a key measure for the shelflife of peanut products.Six peanut varieties were used to make three crosses: cross 1, "qing miaodou×quan zhou ma ke", with O/L 5.85 and 1.53 respectively; cross 2, "fuchuan da peanut×long an bao peanut", with O/L 5.49 and 1.92 respectively;and cross 3, "shanyou 162×Sunoieic 95R". The former 4 parents wereChinese dragon type and SunOleic 95R was a high oleate mutant developedby the University of Florida, in which the polyunsaturated fatty-acylcontent of the seed oil was greatly reduced and contained 80.6% oleate and2.8% linoleate. Shanyou162 was a Spanish type with O/L 1.12.The fatty acid component of the parents and the derived F₂ seeds weredetermined by gas chromatography and the genetics of O/L ratio wasanalysed. The results indicated that the frequency distribution of O/L ratioin F₂ generations of three crosses is continous, showing that the inheritanceO/L is controlled by complex genes. "Major gene plus polygenes model" analysis indicated that, in the first two crosses,inheritance of O/L was controlled by one major gene with minus dominanceeffect plus ploygenes,while in the third cross, the O/L ratio was controlledby two major genes in an additive-dominance-epistatic manner plusploygenes, the estimated additive effects of the two major genes, d_a and d_bwere 1.3586,1.3580, respectively. Heritability values of the major genes ofthree crosses were estimated as 61.27%,64.09% and 64.66%, respectively,and those of polygenes were 33.85%,34.52% and 33.45%, respectively.In breeding program, direct selection for O/L trait was difficultbecause the fatty acid could not be detected until pod harvest andmarker-assisted-selection (MAS) may be more applicable. In order tosearch for genetically linked markers to the target gene, BSA, AFLP andISSR molecular marker technologies were used for polymorphic analysis inshanyou162 and Sunoleic95R and their F₂ segregation population. Themain results were as follows:(1) EcoR I/Mse I: of the 240 primer combinations used, 90 of themdetected 174 polymorphic bands and the polymorphism frequencywas 0.0145%, averaged 1-3 polymorphism per primer pair;(2) pst I/ Mse I: 96 pairs of primers were analysed and 34 werepolymorphic and a total of 76 polymorphic AFLP markers wereobtained;(3) pst I/Taq I: 28 AFLP primer pairs out of 96 primers used detected a total of 61 polymorphic AFLP markers averaged 1-8polymorphism per primer pair;.(4) To transfer the AFLP markers to SCAR, 72 polymorphic AFLPbands recovered from the PAGE plate, cloning and verificationwork will be done later.