An international team of researchers has produced complete, gap-free genome sequences for six peanut varieties, including two wild ancestors and four cultivated lines. The findings, published in Nature Genetics, included an analysis of DNA from 521 peanut accessions globally and identified genetic variants associated with seed oil content and seed size.
Genome Sequencing and Analysis
Scientists from Murdoch University, Peking University, Guangxi Provincial Academy of Agricultural Sciences, Shandong Academy of Agricultural Sciences, and Zhejiang University participated in the study.
- Sequencing scope: The team completed telomere-to-telomere (T2T) genome assemblies for six peanut varieties, covering approximately 100% of nucleotide sequences from chromosome tip to tip.
- Reference genomes: Reference genomes for two peanut subspecies were developed for the first time.
- Population resequencing: DNA from 521 global peanut accessions was analyzed to identify genetic variants linked to agronomic traits.
Previous peanut genome sequencing efforts had left gaps due to repetitive DNA. The new T2T assembly method addressed this challenge.
Key Genetic Findings
- Gene AhWRI1: Researchers identified a gene associated with seed oil content. Peanut lines carrying one version of the gene had an average oil content of approximately 54%, compared to 48% for lines carrying the alternative version—a difference of approximately six percentage points.
- Gene AhGSA1: A gene associated with seed size was identified. Lines carrying one version of the gene averaged 846 grams per 1,000 seeds, compared to 491 grams for the alternative version—a difference of approximately 72%.
- Structural variation: The study detected a large DNA segment that is present in all sampled plants of subspecies var. hirsuta but is largely absent from var. hypogaea. This segment contains genes related to plant architecture and lipid metabolism.
- Asymmetrical evolution: The two halves of the peanut genome (subgenomes) displayed asymmetrical evolution, including differences in repetitive DNA expansion, centromere restructuring, and frequency of structural changes.
"The gap-free reference genome provides a precise genomic toolkit for breeders." — Professor Rajeev Varshney
Background
Cultivated peanut (Arachis hypogaea) is an allotetraploid species derived from two ancestral diploid species. The study is one of the first applications of T2T genome assembly to multiple varieties of a major polyploid crop.
Significance and Applications
Researchers stated that the identified gene variants can be used as DNA markers in breeding programs to develop peanut varieties with higher yields and higher oil content.
Statements
- Professor Rajeev Varshney (Murdoch University) noted that peanut genetics have been challenging to work with compared to most major crops, but the gap-free reference genome provides a precise genomic toolkit for breeders.
- Professor Peter Davies (Murdoch University) highlighted peanuts' role in global food security and nitrogen fixation.
- Professor Peter Eastwood (Murdoch University) described the T2T assembly as a significant achievement, given peanuts' complex tetraploid genome.