A chromosome‐level genome assembly provides insights into ascorbic acid accumulation and fruit softening in guava (Psidium guajava)

Abstract

Summary 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.

A Draft Genome Assembly of “Cas” (Psidium Friedrichsthalianum (O. Berg) Nied): An Indigenous Crop of Costa Rica Untapped.

“…Partial or complete genome duplication is also a common feature in plant genomes (Wendel et al 2016). The GC content of the Cas draft assembly was 40.05%, similar to that of P. guajava (Feng et al 2020) and E. grandis (Myburg et al 2014), the two most closely related species with sequenced genomes.…”

“…Previous work on the assembly of the complete genome of economically important members of the Myrtaceae, such as Psidium guajava (Feng et al 2020), Eucalyptus grandis (Myburg et al 2014) and Leptospermum scoparium (Mānuka) (Thrimawithana et al 2019) has been published. In this study, we present the rst draft assembly of the Cas genome (P. friedrichsthalianum) using PACBio long reads and the Canu assembly pipeline (Koren et al 2017).…”

Pangenomes as a Resource to Accelerate Breeding of Under-Utilised Crop Species

“…Despite being economically valuable, there are few genomic resources for the species, especially resources that can be used to study the response of guava to biotic and abiotic stresses [ 76 ]. Most genomic resources for guava have only emerged in the early 2020s, including a genome assembly [ 76 , 77 ], high throughput and EST-based InDel/SNP markers [ 76 ] and a transcriptome assembly [ 78 ]. These resources lay the groundwork for improving the agronomic traits of guava by gene mapping and genomic selection that could be expedited through a pangenome.…”

Genomic Approaches for Improvement of Tropical Fruits: Fruit Quality, Shelf Life and Nutrient Content

“…Using AFLP markers, diversity analysis studies grouped the white fleshed and pink fleshed guava varieties in separate groups [ 230 ]. Recently, a major improvement in understanding the molecular mechanisms and genes involved in controlling the ascorbic acid accumulation and fruit softening was brought about by the whole genome sequencing of Psidium guajava [ 231 ]. In the case of jackfruit, genetic diversity analysis has shown that white pulp and firm textured fruit varieties were more genetically diverse compared to red and yellow pulps and soft textured fruits, respectively [ 232 ].…”