Citrus is a source of many nutritional and medicinal advantages, which is cultivated worldwide with major citrus groups of sweet oranges, mandarins, grapefruits, kumquats, lemons and limes. Pakistan produces all of its major citrus groups with mandarin (Citrus reticulata) being the prominent group that includes local commercial cultivars such as Feutral's Early, Dancy, Honey and Kinnow. The present study was designed to understand the genetic architecture of this unique variety of Citrus reticulata -'Kinnow'. The whole-genome resequencing and variant calling was performed to map the genomic variability that might be responsible for its particular characteristics like taste, seedlessness, juice content, thickness of peel and shelf-life. A total of 139,436,350 raw sequence reads using Illumina platform were generated with 20.9 Gb data in Fastq format having 98% effectiveness and 0.2% base call error rate. Overall, a total of 3,503,033 SNPs, 176,949 MNPs, 323,287 INS and 333,083 DEL were identified using the GATK4 variant calling pipeline against Citrus clementina as a reference genome. Further, g:Profiler bioinformatics tool was applied for annotating the newly found variants, harbor genes/transcripts and their involved pathways. A total of 73,864 transcripts harbors 4,336,352 variants, most of the observed variants were predicted in non-coding regions and 1,009 transcripts were found well annotated by different databases. Out of the total aforementioned transcripts, 588 involved in biological processes, 234 in molecular functions and 167 transcripts involved in cellular components in Citrus reticulata. In a nutshell, 18,153 high-impact variants and 216 genic-variants found in the current study which may be used for marker-assisted breeding programs of 'Kinnow' to identify this particular variety among others and to propagate its valued traits to improve the contemporary citrus varieties as well.

Citrus reticulata (Blanco) fruit is native to South East Asia and owns many nutritional, medicinal and economic advantages, which is 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 for this valued variety are lacking due to the in-housed insufficient genomic and technical resources. Therefore, the current research was initiated to provide the baseline 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 a 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 the (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.

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