Peanut (Arachis hypogaea L.) serves as a vital oilseed and food crop worldwide. Embryo abortion reduces seed set in peanut and significantly limits yields, but the mechanisms responsible have remained unclear. Here, we examined an ethyl methanesulfonate (EMS)-induced peanut mutant exhibiting early embryo abortion and a partially single-seeded pod phenotype. Cytological analysis indicated that seed abortion in the mutant begins at the proembryo stage, 7 d after flowering, with noticeable degeneration by 3 d after peg penetration into the soil (DAP), culminating in complete arrest by 10 DAP. Transcriptomic analysis identified 8778 differentially expressed genes (DEGs) during the transition from aerial to subterranean peg development in the mutant. These DEGs were significantly enriched for pathways such as MAPK signaling, auxin biosynthesis and transport, and calcium transport. Notably, we identified a premature stop codon mutation (C > T) in AhZAR1-4 of the mutant; this gene encodes a leucine-rich repeat receptor-like kinase. The mutation resulted in the truncation of the kinase and transmembrane domains of AhZAR1-4, leading to a loss of membrane localization and protein function. In yeast two-hybrid screening, AhZAR1-4 interacted with both AhIAA31 and AhBSK2. Heterologous overexpression of AhZAR1-4_wt successfully rescued the seed-abortion phenotype of the Arabidopsis thaliana atzar1-4 mutant and increased seed size, whereas AhZAR1-4_mut expression did not. These findings identify AhZAR1-4 as a crucial regulator of seed development in peanut, making it a promising genetic target for improving pod yield and seed setting rate.

Pod size is a key agronomic trait that influences peanut yield greatly. However, our understanding of the mechanisms underlying pod size is limited. In this study, we employed a segregating population derived from a cross between the small-pod line ND_S and the large-pod line ND_L to map quantitative trait loci (QTL) associated with pod size. Initial mapping performed using bulk segregant analysis revealed a candidate interval on chromosome A05 referred to as qPSW05. We refined this interval to a 256.9 kb genomic region using newly developed molecular markers. Through sequence and expression analyses, we identified the candidate gene AhXE45GC, which encodes an AN1 zinc finger protein. We discovered a 33-bp insertion in the intron of AhXE45GC in ND_S. Accessions that lack this insertion, such as ND_L, had significantly larger pods than those with the insertion, including ND_S. To facilitate marker-assisted selection for peanut pod size, we developed a molecular marker associated with this polymorphism. This marker could provide a valuable genetic resource for breeding high-yielding peanut varieties.

Peanut (Arachis hypogaea L.) bacterial wilt (BW) is a devastating soil-borne disease caused by Ralstonia solanacearum (RS) that poses a significant threat to peanut yield and quality. Nucleotide-binding leucine-rich repeat (NBS-LRR) proteins are a class of plant-specific immune receptors that recognize pathogen-secreted effector molecules and activate immune responses to resist pathogen infections. However, the precise functions of AhCN genes (where CN is a class of nucleotide-binding site, leucine-rich repeat receptor (NLR) genes that lack LRR structural domains) in peanut plants are not fully understood. In this study, a total of 150 AhCN genes were identified and classified into nine subfamilies based on a systematic phylogenetic analysis. The AhCN genes showed highly conserved structural features, and the promoter cis-elements indicated involvement in plant hormone signaling and defense responses. After inoculation with RS, the highly resistant peanut variety ‘H108’ significantly outperformed the susceptible variety ‘H107’ based on physiological indicators such as plant height, main stem diameter, and fresh weight, likely due to the inhibition of bacterial proliferation and diffusion in the stem vascular bundle. AhCN34 was found to be significantly upregulated in ‘H108’ compared to ‘H107’ during plant infection and in response to treatments with each of three plant hormones. Importantly, AhCN34 overexpression in peanut leaves enhanced their resistance to BW. These findings demonstrate the great potential of AhCN34 for applications in peanut resistance breeding. Our identification and characterization of the AhCN genes provide insights into the mechanisms underlying BW resistance in peanut and can inform future research into genetic methods of improving BW resistance in peanut.

Peanut (Arachis hypogea L.) bacterial wilt (BW) is a devastating disease caused by Ralstonia solanacearum that results in severe yield and quality losses. Plant defensins are short cysteine-rich peptides with antimicrobial activity. The role of defensin genes (AhDef) in peanut is unclear. A genome-wide investigation of AhDef genes was undertaken, and 12 identified AhDef genes were classified into two groups containing the gamma-thionin domain formed by four disulfide pairs: Cys1-Cys8, Cys2-Cys5, Cys3-Cys6, and Cys4-Cys7. In silico analysis revealed that AhDef genes showed highly conserved architectural features and contained cis-elements associated with phytohormone signaling and defense responses. A highly resistant cultivar, H108 (R) and a susceptible accession, H107 (S) were tested by R. solanacearum inoculation. H108 (R) showed fewer symptoms than H107 (S) owing to inhibition of bacterial reproduction and spread in the vascular bundles of roots and stems. In a transcriptomic expression profile, AhDef genes, particularly AhDef1.6 and AhDef2.2, were up-regulated in H108 (R) compared with H107 (S) under R. solanacearum infection and phytohormone treatment. Subcellular localization showed that the AhDef1.6 and AhDef2.2 proteins were both expressed specifically on the plasma membrane. Overexpression of protein fusion AhDef2.2-YFP in Nicotiana benthamiana and peanut leaves increased resistance to R. solanacearum, suggesting its role in response to BW infection. AhDef2.2 may be valuable for peanut resistance breeding.