关键词: 桃, CCD4, 分子辅助选种, 果肉颜色

Abstract:

【Objective】It shows that peach flesh color (yellow/white) is controlled by the gene CCD 4 (carotenoid cleavage dioxygenase 4). Based on three types of CCD4 allele variations, molecular markers of indel, SSR-CE, and Sanger sequence for SNP were used to analyze the genotypes of 122 peach cultivars (lines), with the aim to determine the correlation between flesh color and genetic variation. This result could provide information for parental matching and the selection of corresponding molecular markers for phenotyping in their offspring. 【Method】Three types of variations were detected via PCR. LTR transposable element insertion was detected by 1% agarose gel electrophoresis, and SSR repeat numbers were detected using CE-SSR in ABI3730XL. Nucleotide substitution was detected using the Sanger sequence and analyzed with the ContigExpress software. In total, the genotypes of 122 cultivars (lines) were analyzed, and the correlation between phenotype and genetic variation was determined.【Result】After genotyping of the 122 cultivars, it was found that 31 accessions were LTR transposable element insertions with 729-bp amplified fragments, accounting for 25.4% of the total accessions, of which eight accessions (25.8%) were homozygous. Sixty-eight cultivars (lines) were SSR repeat number variations, accounting for 55.7% of the total accessions and including 25 (36.8%) homozygous types with 2-bp insertions. Of the 122 cultivars (lines), only one cultivar (Fertilia Morettini) was caused by nucleotide substitution and SSR repeat number variation, accounting for 0.82%, which was not widely used in the breeding program. LTR transposable element insertion and SSR repeat number variation were the key types affecting flesh color. Of the 122 cultivars (lines), seven yellow-flesh cultivars (lines) were caused by SSR repeat number variation and LTR transposable element insertion, accounting for 5.7%. One homozygous or two heterozygous sequence variations were both responsible for yellow flesh. The results showed that genotypes were identical with phenotypes of the 122 accessions, with 100% accuracy. 【Conclusion】The genotypes of 122 peach cultivars (lines) (white and yellow flesh color) were identified using molecular markers, which could be applied for parental selection, offspring identification in breeding programs, and flesh color selection (white or yellow) using molecular marker-assisted selection.

Key words: peach, CCD4, MAS, flesh color