1 | INTRODUCTION
Mungbean (Vigna radiata [L.]) is an important legume crop which widely cultivated in South and East Asia countries including India, Myanmar, China, Thailand, Bangladesh, Pakistan and Indonesia (Breria et al. 2020a; Keatinge et al. 2011). It is also widely planted in Tanzania and Kenya in recent years, but the average yield is still low (Nair & Schreinemachers 2020). Mungbean is also act as an important rotation crop due to short-duration (maturing in 60 to 75 days), drought tolerance, and ability to fix nitrogen as other legume crops. Mungbean seeds contain relatively high proportion of easily digestible proteins (24%), act as important sources of hunman dietary proteins and carbohydrates, while its sprouts are popular and inexpensive vegetable rich with vitamin C and folate (Keatinge et al. 2011).
The draft genome sequence of mungbean was assembly of a widely grown cultivar VC1973A (Kang et al. 2014). This initial reference enabled rapid progress in genetic and genomic researches with the aim to understand leaf development (Jiao et al. 2016), Powdery Mildew Resistance (Yundaeng et al. 2020), bruchid resistance (Chotechung et al. 2016; Kaewwongwal et al. 2017), salinity tolerance (Breria et al. 2020b), genomic diversity and Genome-Wide Association Studies (GWAS) investigated seed coat luster (Breria et al. 2020a). The assembly based on Illumina short‐reads technology and consists of 2,748 scaffolds with a N50 of 1.52 Mb, there still about 130 Mb of unmapped scaffolds (Kang & Ha 2020). The low contiguity of the current assembly has limited its application for further fine mapping and candidate genes clone. Thus, a high-quality re-sequencing genome assembly of mungbean is needed.
In this study, we constructed a highly accurate, contiguous, chromosome-scale de novo assembly of the mungbean genome obtained by integrating short-read sequencing, Oxford Nanopore sequencing based gap closure, scaffolding, and orientation based on 3D proximity information derived from chromosome conformation capture (Hi-C) data. The contiguity of the newly assembled genome was 27.86-fold greater than that of the published draft genomes of Vigna radiata (scaffold N50 = 42.35 Mb versus 1.52 Mb). The total size of connective N sequences in the oriented genome assembly was dramatically reduced to 7.2 Kb. The genomic data will provide valuable resources for genetic study of mungbean.