| Sweet and acid makes a major contribution to the flavor and economic value of peach fruit, it also takes as a significant value in breeding. Now, the biological and genetic bases of fruit qauality are still poorly known. The non-acid character of fruit was reported to be controlled by a single dominant gene D, but there was no report about molecular marker which tightly linked to D gene. In this research molecular markers linked to non-acid /acid character in peach fruit were detected with RAPD and AFLP markers in 69 F1 population hybrided from the intraspecific cross between peach cultivars 'Jingyu' and 'Flavortop'. At the same time, A molecular marker linkage map was constructed in F2 population which derived from the cross of 'Okubo' and 'Xingjing nectarine'. The main results were as follows:(1) RAPD marker were used to screen markers linked to the non-acid/acid traits in a pair of bulked samples. Of 301 random primers, only pirmer 8332 produced a polymorphic band which cosegregated with non-acid fruit character, high recombination ratio of specific fragment was 28.9%. Low polymorphism detected by RAPD showed that RAPD technique was not fit for selection of DNA molecular markers tightly linked to non-acid/acid of fruit in the population used in this research.(2) The stable and high efficient AFLP analysis system of peach genome DNA was established: high quality of genome DNA is a critical factor for AFLP analysis; preamplification primers combination E+O/M+0 and E+0/M+1 showed no significant difference on number of band; selective amplification primers combination E+2/M+3 and E+3/M+3 were both suitable for comparision analysis of peach genome. But when E primer had two selective bases, it produced more polymorphism bands. Silver-staining were used in AFLP analysis. Low cost, short time for detecting, free of isotope contamination, long time of preserving and convenience for recovery, all proved that silver-staining was a safe and effective detecting method.(3) Utilizing AFLP technique with BSA method to screen molecular markers linked to non-acid/acid traits of peach fruit. Among 128 pairs of primer combination, three of them amplified specific fragments. Two specific fragments linked to recessive d location of D/d gene derived from primers combination E-TA/M-CTC and E-AT/M-CTA, the linkage distance were 1.47cM and 2.99cM respectively. Primers combination E-ACT/M-CATamplified one specific fragment which linked to dominant D location of D/d gene, linkage distance of was 16.2 cM.(4) The D gene linkage groups were established, two nearest markers AFTA-crc and AFAT-CTA located in two sides of D/d locus respectively.(5) Three specific fragments were coloned and sequenced, the results of sequencing showed that fragment A, B and C all were digested by both EcoR I and Mse I , and were 140bp,199bp,408bp in length respectively. It was infered that fragments B, C might contain elements which relevant to regulation of sugar content by utilizing sequence analyse software. Specific primers of A1/A2, B1/B2, C1/C2 were designed according to sequence. Genome DNA amplified two bands-188bp and 158bp in FI acid individuals, and one band-188bp F1 in non-acid individuals with primers of 61/82, so 158bp band was linked to the recessive d location. The results detected by primers B1/B2 was in agreement with AFLP analysis, AFLP marker AFAT-CTA was converted to SCAR maker successfully. Polymorphism bands disappeared in parents and progeny amplified by primers A1/A2 and C1/C2.(6) SCAR primers of B1/B2 were tested in part of F2 progeny of 'Okubo' and 'Xingjin nectarine'. The results showed that genotype and phenotype was in accordance with each other. This marker could distinguish between heterozyous and homozygous, it was a codominant marker.(7) Linkage map of peach was constructed with AFLP, SSR, RAPD and SCAR markers in 109 F2 population derived from the cross of 'Okubo' and 'Xingjin nectarine'. Polymorphism of parents was analysized with 128 pairs of AFLP prime...
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