Fine mapping and identification of the candidate gene BFS for fruit shape in wax gourd (Benincasa hispida).

Zhikui Cheng,Liwen Su,Yuanchao Xu,Jiquan Gou,Wenjin Yu,Jieying Chen,Wenting Wu,Zhengguo Liu,Yong Chen,Peng Wang,Lianlian Ma

doi:10.1007/s00122-021-03942-8

Abstract

Non-synonymous mutations in the BFS gene, which encodes the IQD protein, are responsible for the shape of wax gourd fruits. Fruit shape is an important agronomic trait in wax gourds. Therefore, in this study, we employed bulked segregant analysis (BSA) to identify a candidate gene for fruit shape in wax gourds within F2 populations derived by crossing GX-71 (long cylindrical fruit, fruit shape index = 4.56) and MY-1 (round fruit, fruit shape index = 1.06) genotypes. According to BSA, the candidate gene is located in the 17.18Mb region on chromosome 2. Meanwhile, kompetitive allele-specific PCR (KASP) markers were used to reduce it to a 19.6Kb region. Only one gene was present within the corresponding region of the reference genome, namely Bch02G016830 (designated BFS). Subsequently, BFS was sequenced in six wax gourd varieties with different fruit shapes. Sequence analysis revealed two non-synonymous mutations in the round wax gourd and one non-synonymous mutation in the cylindrical wax gourd. Quantitative real‑time PCR (qRT-PCR) analysis further showed that the expression of BFS in round fruits was significantly higher than in long cylindrical fruits at the ovary formation stage. Therefore, BFS is a candidate gene for determination wax gourd shape. The predicted protein encoded by the BFS gene belongs to the IQ67-domain protein family, which have the structural characteristics of scaffold proteins and coordinate Ca2+ CaM signaling from the membrane to the nucleus. Ultimately, two derived cleaved amplified polymorphic sequence (dCAPS) markers were developed to facilitate marker-assisted selection for wax gourds breeding.

Highlights

Wax gourds [Benincasa hispida (Thunb) Cogn. (2n = 2x = 24)] are an important crop plant species in the Cucurbitaceae family
Because there was no significant increase in fruit shape index in either GX-71 or MY-1 at 15 days post pollination, FSI was measured at this stage (Fig. 1a)
A candidate gene for wax gourd fruit shape was identified on chromosome 2, indicating that the gene for fruit shape is distinct from for fruit weight, fruit length, fruit diameter, and flesh thickness

Summary

Introduction

Fruit shape is a vital characteristic trait of wax gourds, which exhibit a broad range of phenotypical variations. The genes and quantitative trait loci (QTLs) that control fruit shape have been identified in many crops. SUN, OVATE, FASCIATED (FAS), and LOCULE NUMBER (LC) have all been identified as genes that affect tomato fruit size and shape (Liu et al 2002; Cong et al 2008; Xiao et al 2008; Munos et al 2011). QTL fs8.1, which can induce tomatoes to take on lumpy and slightly elongated shapes, and Sov and Sov, which are inhibitors of the OVATE gene, can regulate fruit shape (Clevenger 2012; Rodríguez et al 2013). The Cla017257 allele causes other variations in fruit shape (Legendre et al 2020)

Methods

Results

Conclusion