Plant Genomics Section, Parco Tecnologico Padano, Lodi 26900, Italy.
BMC Plant Biol. 2013 Oct 22;13:166. doi: 10.1186/1471-2229-13-166.
Maturity date (MD) is a crucial factor for marketing of fresh fruit, especially those with limited shelf-life such as peach (Prunus persica L. Batsch): selection of several cultivars with differing MD would be advantageous to cover and extend the marketing season. Aims of this work were the fine mapping and identification of candidate genes for the major maturity date locus previously identified on peach linkage group 4. To improve genetic resolution of the target locus two F2 populations derived from the crosses Contender x Ambra (CxA, 306 individuals) and PI91459 (NJ Weeping) x Bounty (WxBy, 103 individuals) were genotyped with the Sequenom and 9K Illumina Peach Chip SNP platforms, respectively.
Recombinant individuals from the WxBy F2 population allowed the localisation of maturity date locus to a 220 kb region of the peach genome. Among the 25 annotated genes within this interval, functional classification identified ppa007577m and ppa008301m as the most likely candidates, both encoding transcription factors of the NAC (NAM/ATAF1, 2/CUC2) family. Re-sequencing of the four parents and comparison with the reference genome sequence uncovered a deletion of 232 bp in the upstream region of ppa007577m that is homozygous in NJ Weeping and heterozygous in Ambra, Bounty and the WxBy F1 parent. However, this variation did not segregate in the CxA F2 population being the CxA F1 parent homozygous for the reference allele. The second gene was thus examined as a candidate for maturity date. Re-sequencing of ppa008301m, showed an in-frame insertion of 9 bp in the last exon that co-segregated with the maturity date locus in both CxA and WxBy F2 populations.
Using two different segregating populations, the map position of the maturity date locus was refined from 3.56 Mb to 220 kb. A sequence variant in the NAC gene ppa008301m was shown to co-segregate with the maturity date locus, suggesting this gene as a candidate controlling ripening time in peach. If confirmed on other genetic materials, this variant may be used for marker-assisted breeding of new cultivars with differing maturity date.
成熟日期（MD）是新鲜水果营销的关键因素，特别是那些货架期有限的水果，如桃（Prunus persica L. Batsch）：选择几个具有不同 MD 的品种将有利于覆盖和延长营销季节。本工作的目的是精细定位和鉴定先前在桃连锁群 4 上鉴定的主要成熟日期基因座的候选基因。为了提高目标基因座的遗传分辨率，分别使用 Sequenom 和 9K Illumina Peach Chip SNP 平台对来自 Contender x Ambra（CxA，306 个个体）和 PI91459（NJ Weeping）x Bounty（WxBy，103 个个体）杂交的两个 F2 群体进行了基因型分析。
WxBy F2 群体中的重组个体将成熟日期基因座定位到桃基因组的 220kb 区域。在这个区间内的 25 个注释基因中，功能分类将 ppa007577m 和 ppa008301m 鉴定为最可能的候选基因，它们都编码 NAC（NAM/ATAF1，2/CUC2）家族的转录因子。对四个亲本的重测序，并与参考基因组序列进行比较，发现 ppa007577m 的上游区域有一个 232bp 的缺失，该缺失在 NJ Weeping 中是纯合的，在 Ambra、Bounty 和 WxBy F1 亲本中是杂合的。然而，这种变异在 CxA F2 群体中没有分离，因为 CxA F1 亲本是参考等位基因的纯合子。因此，第二个基因被作为成熟日期的候选基因进行了检查。对 ppa008301m 的重测序显示，最后一个外显子中有一个 9bp 的框内插入，该插入与 CxA 和 WxBy F2 群体中的成熟日期基因座共分离。
使用两个不同的分离群体，成熟日期基因座的图谱位置从 3.56Mb 细化到 220kb。在 NAC 基因 ppa008301m 中的一个序列变异与成熟日期基因座共分离，表明该基因是控制桃成熟时间的候选基因。如果在其他遗传材料上得到证实，这种变异可以用于具有不同成熟日期的新品种的标记辅助育种。
