A Detailed Analysis of the BR1 Locus Suggests a New Mechanism for Bolting after Winter in Sugar Beet (Beta vulgaris L.)

Abstract

Sugar beet (Beta vulgaris ssp. vulgaris) is a biennial, sucrose-storing plant, which is mainly cultivated as a spring crop and harvested in the vegetative stage before winter. For increasing beet yield, over-winter cultivation would be advantageous. However, bolting is induced after winter and drastically reduces yield. Thus, post-winter bolting control is essential for winter beet cultivation. To identify genetic factors controlling bolting after winter, a F2 population was previously developed by crossing the sugar beet accessions BETA 1773 with reduced bolting tendency and 93161P with complete bolting after winter. For a mapping-by-sequencing analysis, pools of 26 bolting-resistant and 297 bolting F2 plants were used. Thereby, a single continuous homozygous region of 103 kb was co-localized to the previously published BR1 QTL for post-winter bolting resistance (Pfeiffer et al., 2014). The BR1 locus was narrowed down to 11 candidate genes from which a homolog of the Arabidopsis CLEAVAGE AND POLYADENYLATION SPECIFICITY FACTOR 73-I (CPSF73-I) was identified as the most promising candidate. A 2 bp deletion within the BETA 1773 allele of BvCPSF73-Ia results in a truncated protein. However, the null allele of BvCPSF73-Ia might partially be compensated by a second BvCPSF73-Ib gene. This gene is located 954 bp upstream of BvCPSF73-Ia and could be responsible for the incomplete penetrance of the post-winter bolting resistance allele of BETA 1773. This result is an important milestone for breeding winter beets with complete bolting resistance after winter.

Vernalization Alters Sink and Source Identities and Reverses Phloem Translocation from Taproots to Shoots in Sugar Beet

“…The findings also have implications for agriculture and breeding, where attempts have been made to grow sugar beet over all seasons (Hoffmann and Kluge-Severin, 2011;Hoffmann and Kenter, 2018), a scenario which will become more and more realistic by the generation and employment of bolting-resistant hybrid genotypes (Pin et al, 2010;Pfeiffer et al, 2014;Tränkner et al, 2016).…”

Haplotype Variation of Flowering Time Genes of Sugar Beet and Its Wild Relatives and the Impact on Life Cycle Regimes

“…Hébrard et al ( 2013 ) compared gene expression and DNA methylation profiles of bolting-resistant and bolting-sensitive beet genotypes after vernalization and determined 169 differentially expressed genes and 111 differentially methylated regions as putative bolting loci. The SBT-9 / BR1 locus was discovered to control bolting resistance after winter (Pfeiffer et al, 2014 ), where a homolog of the Arabidopsis CLEAVAGE AND POLYADENYLATION SPECIFIC FACTOR 73-I ( CPSF73-I ) was identified as the most promising candidate gene (Tränkner et al, 2016 ). Recently, Tränkner et al ( 2017 ) proposed that two QTL contribute to variation in seasonal bolting.…”

Beta vulgaris ssp. vulgaris chromosome 8 shows significant association with geosmin concentration in table beet

“…Allele frequency analysis using bulked sequence data is particularly effective in B. vulgaris ssp. vulgaris due to its genetic heterogeneity and the fact that phenotypes are both changed and measured on a population mean basis ( Ries et al 2016 ; Tränkner et al 2016 ; Galewski and Mcgrath 2020 ). This trait-based selective genotyping strategy could be applied to any population yielding two pools with extreme geosmin concentration, including those created for linkage mapping or GWAS.…”