Browsing by Author "Pradhan, Akshay Kumar"

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    A chromosome-scale assembly of allotetraploid Brassica juncea (AABB) elucidates comparative architecture of the A and B genomes
    (John Wiley & Sons, 2021) Paritosh, Kumar; Yadava, Satish Kumar; Singh, Priyansha; Bhayana, Latika; Mukhopadhyay, Arundhati; Gupta, Vibha; Bisht, Naveen C.; Zhang, Jianwei; Kudrna, David A; Copetti, Dario; Wing, Rod A; Reddy, Vijay Bhaskar; Pradhan, Akshay Kumar; Pental, Deepak
    Brassica juncea (AABB), commonly referred to as mustard, is a natural allopolyploid of two diploid species – B. rapa (AA) and B. nigra (BB). We report a highly contiguous genome assembly of an oleiferous type of B. juncea variety Varuna, an archetypical Indian gene pool line of mustard, with ~100x PacBio single‐molecule real‐time (SMRT) long‐reads providing contigs with an N50 value of >5Mb. Contigs were corrected for the misassemblies and scaffolded with BioNano optical mapping. We also assembled a draft genome of B. nigra (BB) variety Sangam using Illumina short‐read sequencing and Oxford Nanopore long‐reads and used it to validate the assembly of the B genome of B. juncea. Two different linkage maps of B. juncea, containing a large number of genotyping‐by‐sequencing markers were developed and used to anchor scaffolds/contigs to the 18 linkage groups of the species. The resulting chromosome‐scale assembly of B. juncea Varuna is a significant improvement over the previous draft assembly of B. juncea Tumida, a vegetable type of mustard. The assembled genome was characterized for transposons, centromeric repeats, gene content, and gene block associations. In comparison to the A genome, the B genome contains a significantly higher content of LTR/Gypsy retrotransposons, distinct centromeric repeats, and a large number of B. nigra specific gene clusters that break the gene collinearity between the A and the B genomes. The B. juncea Varuna assembly will be of major value to the breeding work on oleiferous types of mustard that are grown extensively in south Asia and elsewhere.