De novo Genome Assembly, Functional Annotation and SSR Mining of Citrus reticulata (Kinnow) from Pakistan

Citrus reticulata (Blanco) fruit is native to South East Asia which owns many of the nutritional, medicinal and economic advantages, locally known as "Kinnow" and one of the priced mandarin varieties (Dancy, Fuetrells Early and Honey) of Citrus genera renowned for its exclusive taste, vitamin richness, thin peel, long shelf-life and seedless characteristics in Pakistan. However, genetic improvement and breeding strategies of this valued variety are lacking due to the in-housed insufficient genomic and technical resources. Therefore, the current research was initiated to provide the base-line de-novo genome assembly of C. reticulata (seedless kinnow) at a depth of 151x with Illumina paired-end short-read sequencing technology using HiSeq 2500. Whole-genome sequencing resulted in 139,436,350 raw reads ([~]20.09 GB) of data, however, after removing the low-quality reads (1.08%), duplicated sequences (10.5%) and Illumina adaptors, 137,901,462 clean reads were obtained with ([~]18.87 GB) of clean data which was further used for downstream variant calling analysis. In total, 348,861 scaffolds were generated with N50 value of 4827 which constitute 263,018,9 contigs ranging from 71-36,213 with total of 179,984,763 nucleotides. The GC content of the final draft assembly at 71-mer was 34.1%. Moreover, annotation was performed with "Hayai-Annotation Plants" tool which marked the whole-genome mapping with three main functional databases of interpro, Pfam and gene ontology. Additionally, in-silico identification of 111,032 Simple Sequence Repeats (SSR) was also accomplished with the help of GMATA tool, which may be used for further screening and genetic improvement of the citrus varieties by means of this current assembly as a resource of local reference genome.