Genetic variation and QTL analysis of saturated fatty acids in two doubled haploid populations of oilseed rape (Brassica napus L.)

Abstract

Consumption of foodstuff with low contents of saturated fatty acids is considered beneficial for human health. Reducing saturated fatty acid content in oilseed rape (canola) and other oil and protein crops is a relevant breeding aim. The objective of this work was to study the genetic variation and inheritance of saturated fatty acids in two DH populations of oilseed rape, to map QTL and to identify candidate genes. In addition, the correlation to other seed quality traits was studied. To this end, two half-sib DH populations were tested in up to five field environments in north-western Europe and seeds harvested from open-pollinated seeds were analyzed. Genotyping was performed using Illumina Brassica 15 K SNP chip. In both populations, significant effects for the genotypes and for the environments were detected, and heritability ranged from 68 to 89% for the predominant palmitic acid and stearic acid content. Up to 48 QTL for different fatty acids, oil and acid detergent lignin (ADL) content were mapped in the two populations. Co-locating QTL for palmitic acid, stearic acid, the C16/18 fatty acid ratio, the FATB/A ratio, oil and ADL content were identified on different chromosomes. A large number of candidate genes were identified within the vicinity of QTL flanking markers. Identification of several co-locating QTL positions, of associated candidate genes and SNP markers should facilitate oilseed rape breeding for low saturated fatty acid content.

Effect of a low seed lignin content on seed yield and quality in winter oilseed rape (Brassica napus)

“…From this cross, the DH line SGEDH13 emerged, with its high oil and reduced lignin content, and was crossed to the oilseed rape cultivar ‘Adriana’, and thus, a further population of DH lines was developed. QTL mapping in this new population confirmed the segregation of that very major QTL for lignin content at the same position at chromosome C05 (Yusuf et al, 2022). The aim of the present study was to analyse expectable effects of that major lignin QTL on field trial‐based seed, oil and protein yield.…”

“…For the whole Adriana × SGEDH13 population, Yusuf et al (2022) found, similar to Behnke et al (2018), negative correlations between ADL content and oil content (−.24**) and protein content (−.33**; pers communication AO Yusuf). However, in the present study, the low ADL bulk had only a non‐significant higher oil content in both populations and a significantly higher protein content was detected only in one population.…”

“…A candidate gene for the major QTL for low ADL content on chromosome C05 in both populations is the phenylalanine ammonia‐lyase BnaPAL4 gene (Behnke et al, 2018; Ding et al, 2021; Wang et al, 2015; Yusuf et al, 2022). It catalyses the first step in the phenylpropanoid pathway leading to flavonoid‐ and lignin‐related metabolites (Fraser & Chapple, 2011).…”

“…A low ADL content is associated with less seed coat phenolic compounds and can result in less pigmentation and a lighter seed colour (Wittkop et al, 2012). Because the reduction in ADL content in both populations was not accompanied by a yellow seed phenotype (Behnke et al, 2018;Yusuf et al, 2022), the cause is probably a mutation in BnaPAL4. However, a complete loss of function in BnaPAL4 is not present, because lignin in seed coats is still produced.…”

“…The plant material of oilseed rape ( Brassica napus ; 2n = 38 AACC) used in the field trials was derived of the cross SGDH14 × Express 617 ( n = 139) (Behnke et al, 2018) and of the cross Adriana × SGEDH13 ( n = 172) (Yusuf et al, 2022). In 2018, 12 DH lines with low seed lignin content (5%–7%) and 12 DH lines with high seed lignin content (9%–11%) with similar flowering time and plant height were bagged to secure self‐pollination in both crosses.…”