Sweet cherry is very appreciated by consumers because of its attractive appearance and taste, which is determined by the balanced sweet-sour flavor. In this work, the genetics of soluble solid content (SSC), titratable acidity (TA), sugars and organic acids was investigated in sweet cherry to facilitate breeding improvement for fruit quality. The fruits of five sweet cherry populations (N = 372), three F1 and two F2, were sampled over two years to evaluate SSC, TA, and the content of individual sugars (glucose, fructose, sorbitol, and sucrose) and organic acids (malic, quinic, oxalic, citric and shikimic) by ultra-performance liquid chromatography (UPLC). Glucose, followed by fructose, was the most abundant sugar, while malic acid was the predominant acid. Sorbitol and malic acid were the most stable compounds between years, and had the highest heritability, being also the best correlated to SSC and TA respectively, revealing their relevance for breeding. Significantly positive correlations were observed among sugars and SSC, and acids and TA, but high interannual variability between years was observed for all traits. QTL mapping for SSC, sugars, TA, and organic acids was performed using a multi-family approach with FlexQTL™. Twenty QTLs were detected consistently during the two phenotyped years, and several relevant regions with overlapping QTLs for sugars and acids were also identified. The results confirmed major stable SSC and TA QTLs on the linkage groups 4 and 6, respectively. Within the main LG4 SSC QTL region, where maturity and fruit development time QTLs have been previously detected, three stable sugar (glucose, sorbitol, and sucrose) and two acid (quinic, shikimic) QTLs were also identified, suggesting a pleiotropic effect of ripening date on the content of these compounds. The major malic acid QTL overlapped with TA QTL on LG6, thus TA QTL mapping in LG6 may correspond to malic acid QTLs. Haplotype analyses of major SSC and sugars QTL in LG4, and TA and malic acid in LG6 revealed haplotypes of breeding interest. Several candidate genes previously identified in other Prunus fruit species, like peach, were found to collocate with the QTLs detected herein. This work reports QTLs regions and haplotypes of sugar and acid content in a Prunus non-climacteric stone fruit for the first time.

中文翻译：

---

甜樱桃 （Prunus avium L.） 中糖和酸含量的遗传学和 QTL 分析


甜樱桃因其迷人的外观和味道而受到消费者的喜爱，这是由平衡的酸甜风味决定的。本研究研究了甜樱桃中可溶性固形物含量 （SSC）、可滴定酸度 （TA） 、糖和有机酸的遗传学，以促进育种品质的改良。在两年内对 5 个甜樱桃种群 （N = 372），即 3 个 F1 和 2 个 F2 的果实进行取样，以超高效液相色谱 （UPLC） 评估 SSC、TA 以及单个糖类（葡萄糖、果糖、山梨糖醇和蔗糖）和有机酸（苹果酸、奎宁、草酸、柠檬酸和莽草酸）的含量。葡萄糖，其次是果糖，是最丰富的糖，而苹果酸是主要的酸。山梨醇和苹果酸是年份间最稳定的化合物，遗传力最高，分别与 SSC 和 TA 的相关性最好，揭示了它们与育种的相关性。在糖和 SSC 以及酸和 TA 之间观察到显著的正相关，但观察到所有性状的年份间差异很大。使用 FlexQTL™ 的多家族方法进行 SSC 、糖、TA 和有机酸的 QTL 定位。在两个表型年份中一致检测到 20 个 QTL，并且还鉴定了几个糖和酸 QTL 重叠的相关区域。结果分别证实了连锁组 4 和 6 上的主要稳定 SSC 和 TA QTL。 在先前已检测到成熟和果实发育时间 QTL 的主要 LG4 SSC QTL 区域内，还鉴定了三个稳定糖（葡萄糖、山梨醇和蔗糖）和两个酸性（奎因、莽草基）QTL，表明成熟日期对这些化合物含量的多效性影响。主要的苹果酸 QTL 与 LG6 上的 TA QTL 重叠，因此 LG6 中的 TA QTL 定位可能对应于苹果酸 QTL。LG4 中主要 SSC 和糖 QTL 以及 LG6 中 TA 和苹果酸的单倍型分析揭示了育种兴趣的单倍型。发现先前在其他李子果实物种（如桃子）中鉴定的几个候选基因与此处检测到的 QTL 并置。这项工作首次报道了李属非更年期核果中糖和酸含量的 QTLs、区域和单倍型。