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.