QTL Mapping for Agronomic and Adaptive Traits Confirmed Pleiotropic Effect of mog Gene in Black Gram [Vigna mungo (L.) Hepper

Prakit Somta,Xin Chen,Jingbin Chen,Tarika Yimram,Chutintorn Yundaeng,Norihiko Tomooka,Xingxing Yuan

doi:10.3389/fgene.2020.00635

Abstract

Organ size and architecture of plants are important traits affecting crop yield and agronomic practices. An induced mutant, multiple-organ gigantism (MOG), of black gram (Vigna mungo) has been obtained, which shows gigantic leaves, fruit, seed, and architecture (plant height) but lower number of pods per plant. These traits are a pleiotropic effect of a single recessive gene, mog. In this study, we investigated variation of 16 agronomic and adaptive traits in a recombinant inbred line (RIL) population derived from a cross between the MOG mutant (V. mungo var. mungo) and wild black gram (V. mungo var. silvestris) accession TC2210 and identified quantitative trait loci (QTLs) controlling those traits to gain a better understanding of the effect of the mog gene on breeding. The results showed that most of the traits (100-seed weight, leaf size, and plant height) showed moderate narrow-sense heritability (h2) (45–65%), while pod size and seed length (SDL) showed high h2 (>75%) and pod dehiscence (shattering), and seed width (SDW) and days to flowering showed low h2 (<35%). The QTLs for the traits were mapped onto a high-density linkage map developed for the RIL population. Inclusive composite interval mapping identified 42 QTLs in total for the 16 traits with number of QTLs per trait ranging from one to six. Major QTLs for the MOG phenotypes were clustered on linkage group (LG) 6, confirming the pleiotropic effect of the mog gene. Effect of the mog gene/QTL for the MOG phenotypic variations was not high, ranging from about 15% in plant height to 40% in leaf size. For 100-seed weight, which is the most interesting trait, the mog gene/QTL contributed about 30% of the total trait variation and showed an additive effect of only 0.51 g, which is only about 1.5-fold higher than that of the other five QTLs detected for this trait. These results indicated that mog gene expression is highly affected by environment and the effect of the gene toward organ size and plant height is not extraordinarily high. Implications of the findings of this study and exploiting of the MOG mutant in breeding were also discussed.

Highlights

Black gram [Vigna mungo (L.) Hepper] is an important legume crop in Asia, especially South Asia and Southeast Asia
We report quantitative trait locus (QTL) mapping of agronomic and adaptive traits in a recombinant inbred line (RIL) population derived from the cross between the mog mutant and wild black gram (V. mungo var. silvestris Lukoki, Maréchal and Otoul)
The h2 of each trait was subsequently calculated using the following formula: h2 = σ2g/[σ2g + (σ2e/r)], where σ2g and σ2e are the variances of the RILs and experimental error, respectively, and r is the number of replicates

Summary

Introduction

Black gram [Vigna mungo (L.) Hepper] is an important legume crop in Asia, especially South Asia and Southeast Asia. The total planting area of black gram is about 5.5 million hectares, concentrated mainly in India, Myanmar, Pakistan, Bangladesh, Nepal, and Thailand. In South Asia, dry black gram seeds are cooked into a thick soup and consumed as a staple dish, while seed flour is used to prepare several dishes and sweets. In some countries such as Thailand and Japan, black gram seeds are preferred in the sprout industry (Somta et al, 2019). The average seed yield of black gram is very low, e.g., about 650–800 kg/ha in India and Thailand

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