Fine mapping and candidate gene analysis of a major locus controlling ovule abortion and seed number per silique in Brassica napus L.

Abstract

Key message A major QTL controlling ovule abortion and SN was ne-mapped to a 80.1-kb region on A8 in rapeseed, and BnaA08g07940D and BnaA08g07950D are the most likely candidate genes.Abstact The seed number per silique (SN), an important yield determining trait of rapeseed, is the nal consequence of a complex developmental process including ovule initiation and the subsequent ovule/seed development. To elucidate the genetic mechanism regulating the natural variation of SN and its related components, quantitative trait locus (QTL) mapping was conducted using a doubled haploid (DH) population derived from the cross between C4-146 and C4-58B, which showed significant differences in SN and aborted ovule number (AON), but no obvious differences in ovule number (ON). QTL analysis identified 19 consensus QTLs for six SN-related traits across three environments. A novel QTL on chromosome A8, un.A8, which pleiotropically controls all these traits except for ON, was stably detected across the three environments.This QTL explained more than 50% of the SN, AON and percentage of aborted ovule (PAO) variations as well as a moderate contribution on silique length (SL) and thousand seed weight (TSW). The C4-146 allele at the locus increases SN and SL but decreases AON, PAO and TSW. Further ne mapping narrowed down this locus into a 80.1-kb interval anked by markers BM1668 and BM1672, and six predicted genes were annotated in the delimited region. Expression analyses and DNA sequencing showed that two homologs of Arabidopsis photosystem I subunit F (BnaA08g07940D) and zinc transporter 10 precursor (BnaA08g07950D) were the most promising candidate genes underlying this locus. These results provide a solid basis for cloning un.A8 to reduce the ovule abortion and increase SN in the yield improvement of rapeseed.

Genetic dissection of the natural variation of ovule number per ovary in oilseed rape germplasm (Brassica napus L.)

“…Furthermore, relative to the leading SNPs of these association loci, a total of 1971 annotated genes were located within 500 kb or LD statistic r 2 > 0.2. A dozen QTL for ONPO have been reported through linkage or association analysis in oilseed rape ( Okada et al, 1991 ; Jiao et al, 2021 ). To determine their positional relationship with the association loci identified in the current research, comparative QTL analysis was conducted based on the reference genome of Darmor_V4.1.…”

“…Ovules are the direct precursors of seeds containing the female gametophytes, which are fecundated during pollination to inaugurate seed development ( Yuan and Kessler, 2019 ). Therefore, increasing the number of ovules per flower has become an important strategy for improving seed crop yield and addressing food security ( Jiao et al, 2021 ). The number of ovules per flower varies considerably across different species and even among the different accessions of the same species ( Burd et al, 2009 ; Khan et al, 2019 ).…”

“…Ovule number per ovary is determined by the ovule initiation process and is significantly affected by flower size and position ( Gomez et al, 2018 ; Yuan and Kessler, 2019 ), nutrient availability ( Strelin and Aizen, 2018 ), and phytohormones levels ( Barro-Trastoy et al, 2020 ; Qadir et al, 2021 ). Although much research into seed number per silique has been reported in B. napus (Yang et al, 2017; Khan et al, 2019 ; Zhu et al, 2020 ), few were performed on ovule number per ovary ( Khan et al, 2019 ; Jiao et al, 2021 ). Therefore, little is known about the natural variation of ovule number per ovary in oilseed rape germplasm.…”

BnaCRCs with domestication preference positively correlate with the seed‐setting rate of canola

“…To determine the variation in BnaSSA07.crc and BnaSSC06.crc genes in the natural population, we designed specific primers (Table S3) to detect the insertion of hAT and EnSpm transposons in BnaSSA07.crc and the variation of the BnaSSC06.crc promoter in 501 natural lines (Jiao et al., 2021; Song et al., 2021). We found that only five and two lines in the natural population contained hAT and EnSpm transposons in BnaSSA07.crc , respectively (Figure 7a; Table S6), which did not exist in B. oleracea , Arabidopsis , and 14 B. rapa cultivars.…”

“…However, 229 lines exhibited BnaSSC06.crc promoter variation (Table S6), indicating that BnaSSC06.crc variation exists widely in the natural population. Based on the phenotypic data of the natural population for 4 years (Jiao et al., 2021), the relationship between the existence of transposons and SS of different lines was analyzed. We found that the SS of the lines containing hAT (1L259, 1L389, 1L434, 1L503, and 1L504) or EnSpm (1L236 and 1L311) transposons was markedly lower than that of the lines (1L148 and 1L149) without transposons (Figure 7a).…”