Transcriptome profiling of two contrasting pigeon pea (Cajanus cajan) genotypes in response to waterlogging stress

Clusterbean ( Cyamopsis tetragonoloba (L.) Taub.), also known as Guar is a widely cultivated dryland legume of Western India and parts of Africa. Apart from being a vegetable crop, it is also an abundant source of a natural hetero-polysaccharide called guar gum or galactomannan which is widely used in cosmetics, pharmaceuticals, food processing, shale gas drilling etc. Here, for the first time we are reporting a chromosome-scale reference genome assembly of clusterbean, from a high galactomannan containing popular guar cultivar, RGC-936, by combining sequenced reads from Illumina, 10x Chromium and Oxford Nanopore technologies. The initial assembly of 1580 scaffolds with an N50 value of 7.12 Mbp was generated. Then, the final genome assembly was obtained by anchoring these scaffolds to a high density SNP map. Finally, a genome assembly of 550.31 Mbp was obtained in 7 pseudomolecules corresponding to 7 chromosomes with a very high N50 of 78.27 Mbp. We finally predicted 34,680 protein-coding genes in the guar genome. The high-quality chromosome-scale cluster bean genome assembly will facilitate understanding of the molecular basis of galactomannan biosynthesis and aid in genomics-assisted breeding of superior cultivars.