Arachis oil liquid

Enhancing seed oil content with desirable fatty acid composition is one of the most important objectives of groundnut breeding programs globally. Genomics-assisted breeding facilitates combining multiple traits faster, however, requires linked markers. In this context, we have developed two different F2 mapping populations, one for oil content (OC-population, ICGV 07368 × ICGV 06420) and another for fatty acid composition (FA-population, ICGV 06420 × SunOleic 95R). These two populations were phenotyped for respective traits and genotyped using Diversity Array Technology (DArT) and DArTseq genotyping platforms. Two genetic maps were developed with 854 (OC-population) and 1,435 (FA-population) marker loci with total map distance of 3,526 and 1,869 cM, respectively. Quantitative trait locus (QTL) analysis using genotyping and phenotyping data identified eight QTLs for oil content including two major QTLs, qOc-A10 and qOc-A02, with 22.11 and 10.37% phenotypic variance explained (PVE), respectively. For seven different fatty acids, a total of 21 QTLs with range 7.6% to 78.6% PVE were identified and 20 of these QTLs were of major effect. Two mutant alleles, ahFAD2B and ahFAD2A, also had 18.44% and 10.78% PVE for palmitic acid, in addition to oleic (33.8% and 17.4% PVE) and linoleic (41.0% and 19.5% PVE) acids. Furthermore, four QTL clusters harbouring more than three QTLs for fatty acids were identified on the three LGs. The QTLs identified in this study could be further dissected for candidate gene discovery and development of diagnostic markers for breeding improved groundnut varieties with high oil content and desirable oil quality.

Abstract licence: CC BY

KEY MESSAGE: ddRAD-seq-based high-density genetic map comprising 2595 loci identified a major and consensus QTL with a linked marker in a 0.8-Mb physical interval for oil content in peanut. Enhancing oil content is an important breeding objective in peanut. High-resolution mapping of quantitative trait loci (QTLs) with linked markers could facilitate marker-assisted selection in breeding for target traits. In the present study, a recombined inbred line population (Xuhua 13 × Zhonghua 6) was used to construct a genetic map based on double-digest restriction-site-associated DNA sequencing (ddRAD-seq). The resulting high-density genetic map contained 2595 loci, and spanned a length of 2465.62 cM, with an average distance of 0.95 cM/locus. Seven QTLs for oil content were identified on five linkage groups, including the major and stable QTL qOCA08.1 on chromosome A08 with 10.14-27.19% phenotypic variation explained. The physical interval of qOCA08.1 was further delimited to a ~ 0.8-Mb genomic region where two genes affecting oil synthesis had been annotated. The marker SNPOCA08 was developed targeting the SNP loci associated with oil content and validated in peanut cultivars with diverse oil contents. The major and stable QTL identified in the present study could be further dissected for gene discovery. Furthermore, the tightly linked marker for oil content would be useful in marker-assisted breeding in peanut.

Abstract licence: CC BY

Peanut kernels rich in oil, particularly those with oleic acid as their primary fatty acid, are sought after by consumers, the food industry, and farmers due to their superior nutritional content, extended shelf life, and health benefits. The oil content and fatty acid composition are governed by multiple genetic factors. Identifying the quantitative trait loci (QTL) related to these attributes would facilitate marker-assisted selection or genomic selection, thus enhancing the quality-focused peanut breeding program. For this purpose, we developed a population of 521 recombinant inbred lines (RIL) and tested their kernel quality traits across five different environments. We identified two major and stable QTLs for oil content (qOCAh12.1 and qOCAh16.1). The markers linked to these QTLs were designed by competitive allele-specific PCR (KASP) and were subsequently validated. Moreover, we found that the superior haplotype of oil content in the qOCAh16.1 region was conserved within the PI germplasm cluster, as evidenced by a diverse peanut accession panel. In addition, we determined that qAh09 and qAh19.1, which harbor the key gene encoding fatty acid desaturase 2 (FAD2), influence all seven fatty acids, including palmitic, stearic, oleic, linoleic, arachidic, gadoleic, and behenic acids. As for protein content and the long-chain saturated fatty acid behenic acid, qAh07 emerged as the major and stable QTLs, accounting for over 10% of the phenotypic variation explained (PVE). These findings would enhance marker-assisted selection in peanut breeding, aiming to improve oil content, and deepen our understanding of the genetic mechanisms that shape fatty acid composition.

Abstract licence: CC BY-NC-ND

High oil content in peanut seeds is a key breeding objective for peanut (Arachis hypogaea L.) quality improvement. In order to explore the genetic basis of oil content in peanuts, a recombinant inbred line (RIL) population consisting of 256 lines was phenotyped across six environments. Continuous distribution and transgressive segregation for both oil content and oleic acid content were demonstrated across all environments. Quantitative trait locus (QTL) analysis yielded 15 additive QTLs explaining 4.34 to 23.10% of phenotypic variations. A novel stable and major QTL region conditioning oil content (qOCB09.1) was mapped to chromosome B09, spanning a 1.99 Mb genomic region with 153 putative genes, including the oleic acid gene FAD2B, which may influence the oil content. Candidate genes were identified and diagnostic markers for this region were developed for further investigation. Additionally, 18 pairs of epistatic interactions involving 35 loci were identified to affect the oil content, explaining 1.25 to 1.84% of phenotypic variations. These findings provide valuable insights for further map-based cloning of favorable alleles for oil content in peanuts.

Abstract licence: CC BY

Peanut (Arachis hypogaea L.) is one of the major oil crops and is the fifth largest source of plant oils in the world. Numerous genes participate in regulating the biosynthesis and accumulation of the storage lipids in seeds or other reservoir organs, among which several transcription factors, such as LEAFY COTYLEDON1 (AtLEC1), LEC2, and WRINKLED1 (WRI1), involved in embryo development also control the lipid reservoir in seeds. In this study, the AtLEC1 gene was transferred into the peanut genome and expressed in a seed-specific manner driven by the NapinA full-length promoter or its truncated 230-bp promoter. Four homozygous transgenic lines, two lines with the longer promoter and the other two with the truncated one, were selected for further analysis. The AtLEC1 mRNA level and the corresponding protein accumulation in different transgenic overexpression lines were altered, and the transgenic plants grew and developed normally without any detrimental effects on major agronomic traits. In the developing seeds of transgenic peanuts, the mRNA levels of a series of genes were upregulated. These genes are associated with fatty acid biosynthesis and lipid accumulation. The former set of genes included the homomeric ACCase A (AhACC II), the BC subunit of heteromeric ACCase (AhBC4), ketoacyl-ACP synthetase (AhKAS II), and stearoyl-ACP desaturase (AhSAD), while the latter ones were the diacylglycerol acyltransferases and oleosins (AhDGAT1, AhDGAT2, AhOle1, AhOle2, and AhOle3). The oil content and seed weight increased by 4.42%–15.89% and 11.1%–22.2%, respectively, and the levels of major fatty acid (FA) components including stearic acid, oleic acid, and linoleic acid changed significantly in all different lines.

Abstract licence: CC BY