Guava (Psidium guajava) is an important fleshy‐fruited tree of the Myrtaceae family that is widely cultivated in tropical and subtropical areas of the world and has attracted considerable attention for the richness of ascorbic acid in its fruits. However, studies on the evolution and genetic breeding potential of guava are hindered by the lack of a reference genome. Here, we present a chromosome‐level genomic assembly of guava using PacBio sequencing and Hi‐C technology. We found that the genome assembly size was 443.8 Mb with a contig N50 of ~15.8 Mb. We annotated a total of 25 601 genes and 193.2 Mb of repetitive sequences for this genome. Comparative genomic analysis revealed that guava has undergone a recent whole‐genome duplication (WGD) event shared by all species in Myrtaceae. In addition, through metabolic analysis, we determined that the L‐galactose pathway plays a major role in ascorbic acid biosynthesis in guava fruits. Moreover, the softening of fruits of guava may result from both starch and cell wall degradation according to analyses of gene expression profiles and positively selected genes. Our data provide a foundational resource to support molecular breeding of guava and represent new insights into the evolution of soft, fleshy fruits in Myrtaceae.

中文翻译：

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染色体水平的基因组装配可提供有关番石榴中抗坏血酸积累和果实软化的见解（Psidium guajava）

芭乐（番石榴）是桃金娘科重要的果肉树，广泛种植于世界的热带和亚热带地区，并因其果实中抗坏血酸的丰富而备受关注。但是，缺乏参考基因组阻碍了番石榴的进化和遗传育种潜力的研究。在这里，我们介绍了使用PacBio测序和Hi-C技术的番石榴的染色体级基因组组装。我们发现基因组装配大小为443.8 Mb，重叠群N50为〜15.8 Mb。我们注释了该基因组的总共25 601个基因和193.2 Mb的重复序列。比较基因组分析表明，番石榴科最近经历了桃金娘科所有物种共有的全基因组复制（WGD）事件。此外，通过代谢分析，我们确定L-半乳糖途径在番石榴果实抗坏血酸的生物合成中起主要作用。此外，根据对基因表达谱和阳性选择基因的分析，番石榴果实的软化可能是淀粉和细胞壁降解所致。我们的数据为支持番石榴分子育种提供了基础资源，并代表了对桃金娘科中柔软多肉的果实进化的新见解。