Whole-Genome Sequencing of a Year-Round Fruiting Jackfruit Variety Reveals Very High Single Nucleotide Polymorphisms in Inter-Genic Regions

Background Jackfruit (Artocarpus heterophyllus Lam.) is a tropical and sub-tropical fruit tree distributed in Asia, Africa, and South America. It is the national fruit of Bangladesh and produces fruit in the summer season only. However, a year-round jackfruit variety, BARI Kanthal-3 developed by Bangladesh Agricultural Research Institute (BARI) provides fruits from September to June. This study aimed to evaluate the agronomic performance of BARI Kanthal-3 and to generate a draft whole genome sequence to obtain molecular insights of this important unique variety. Results Number of fruits, average each fruit weight, fruit yield per plant, edible portion in fruit and ß carotene content of BARI Kanthal-3 (n = 5) were 422/plant/year, 5.60 kg, 236.32 kg/year, 53.5% and 3614 mg/100g, respectively. During de novo assembly, 817.7 Mb of the BARI Kanthal-3 genome was scaffolded. However, in the reference-guided genome assembly, almost 843 Mb of the BARI Kanthal-3 genome was scaffolded. Through BUSCO assessment, 97.2% of the core genes were represented in the assembly with 1.3% and 1.5% either fragmented or missing, respectively. By comparing the single copy orthologues (SCOs) in three closely and one distantly related species of BARI Kanthal-3, 706 SCOs were found to be shared across the genomes of the five species. The phylogenetic analysis of the shared SCOs showed that A. heterophyllus is the closest species to BARI Kantal-3. The estimated genome size of BARI Kanthal-3 was 1.04 giga base pairs (Gbp) with a heterozygosity rate of 1.62%. The estimated GC content was 34.10%. Variant analysis revealed that BARI Kanthal-3 includes 5.7 M (35%) and 10.4 M (65%) simple and heterozygous single nucleotide polymorphisms (SNPs), and about 90% of all these polymorphisms are located in inter-genic regions. Conclusion The whole-genome sequence of A. heterophyllus cv. BARI Kanthal-3 reveals extremely high single nucleotide polymorphisms in inter-genic regions. The findings of this study will help better understanding the evolution, domestication, phylogenetic relationships, year-round fruiting and the markers development for molecular breeding of this highly nutritious fruit crop.