Jing Yu

The cultivated peanut (Arachis hypogaea L.) is a globally important oilseed and economic crop, but its narrow genetic base limits breeding progress. Wild Arachis species represent valuable genetic resources for enhancing the resilience of the peanut cultigen. While wild species from section Arachis are widely used in breeding programs, the detection of alien chromosomes in hybrids remains challenging due to limited molecular tools. In this study, a cost-effective and efficient system was established for generating species-specific molecular markers using low-coverage next-generation sequencing data, bypassing the need for whole-genome assembly. Utilizing the Chorus2 software, specific alien-chromosome oligo (SAO) markers were developed for four wild species, A. duranensis (accession A19), A. pusilla (A10), A. appresipilla (A33), and A. glabrata (G2 and G3). A total of 1166 primer pairs were designed, resulting in 220 SAO markers specific to A. duranensis, 77 to A. pusilla, 112 to A. appresipilla, 69 to A. glabrata G2, and 59 to A. glabrata G3, with the highest development efficiency observed in A. duranensis (55.0%). These markers span all chromosomes of the five wild accessions. Genome-wide, chromosome-specific SAO markers enable the efficient detection of introgressed alien chromosomes and provide insight into syntenic relationships among homoeologous chromosomes. These markers offer an effective tool for identifying favorable genes and facilitating targeted introgression for the genetic improvement of the cultivated peanut.

Endophytic bacteria play an important role in the growth, stress tolerance, and metabolic function of salt-tolerant peanuts, yet their community assembly across different saline–alkali soils and plant organs remains poorly characterized. In this study, the V3–V4 variable region of the endophytic bacteria 16S rRNA gene in three organs (roots, leaves, and pods) of high-oleic-acid peanut variety Huayu9118 from three saline–alkali locations (Xinjiang, Jilin, and Shandong, China) was analyzed by high-throughput sequencing. A total of 1,360,313 effective sequences yielded 19,449 amplicon sequence variants (ASVs), with Proteobacteria (45.86–84.62%), Bacteroidota (6.52–13.90%), and Actinobacteriota (3.97–10.87%) dominating all samples. Niche strongly influenced microbial diversity: the roots exhibited the highest level of richness (Chao 1/ACE indices), while the leaves showed the greatest diversity (Shannon/Simpson indices) in XJ samples. Significant compositional differences were observed between aerial (leaves) and underground (roots/pods) organs. Geographic location also markedly shaped endophytic communities, with stronger effects in roots and pods than in leaves—a pattern supported by PCoA combined with ANOSIM (R (roots) = 1, R (pods) = 0.874, R (leaves) = 0.336, respectively, p < 0.001). Saline–alkali adaptation led to a marked enrichment of Novosphingobium in roots and pods and of Halomonas in leaves compared to non-saline–alkali-grown peanuts. Furthermore, the endophytic communities within the same organ type varied significantly across the three saline–alkali sites. Redundancy analysis (RDA) identified the key environmental factors shaping bacterial community composition in the root samples from each location: available phosphorus (AP) and sulfate (SO₄²⁻) were the strongest predictors in XJ; available potassium (AK) and chloride (Cl⁻) in DY; and hydrolyzed nitrogen (HN), pH, soil organic matter (SOM), and bicarbonate (HCO₃⁻) in JL. These findings demonstrate that niches and geographical conditions determined the composition and relative abundance of endophytic bacteria in salt-tolerant peanuts, providing new insights into microbial ecological adaptation in saline–alkali ecosystems.

Peanut is a vital cash crop globally, and enhancing its seed protein content is essential for nutritional security. However, the genetic basis of seed protein content in peanut remains unclear. In this study, bulked segregant analysis combined with next-generation sequencing (BSA-Seq) was employed to isolate a candidate gene, AhSPC, associated with peanut seed protein content. Its function was then characterized in Arabidopsis thaliana through CRISPR/Cas9-mediated gene knockout and overexpression analysis. Gene editing of the homologous gene in Arabidopsis significantly reduced seed protein content in six lines, while two lines showed no obvious change. Overexpression of the AhSPC gene in Arabidopsis led to an increase in seed protein content in three transgenic lines, but some lines showed no significant change, or even a decrease. These inconsistent results might be attributed to functional redundancy, epigenetic modifications, resource competition, or feedback regulation mechanisms within the protein synthesis pathway. This study provides insights into the molecular mechanisms of peanut seed protein content regulation and offers a potential genetic target for molecular breeding.

Peanut is a key cash crop worldwide, yet the limited availability of functional genes and markers for breeding hinders further progress, largely due to the lack of an efficient and user-friendly transformation system. This study aimed to comprehensively evaluate the effectiveness of nodal agroinjection, a novel transformation technique we developed for peanut, by introducing the soybean cold-tolerance gene SCTF-1. Putative transgenic seeds and seedlings were screened using genomic DNA PCR, while transgene expression was analyzed via qRT-PCR and phenotypic assessments. Southern blotting confirmed the stable integration of SCTF-1. The transgenic seedlings displayed enhanced chilling tolerance, characterized by increased proline accumulation, reduced malondialdehyde (MDA), and elevated peroxidase (POD) activity. These findings demonstrate that nodal agroinjection is an efficient and reliable approach for generating transgenic peanut and analyzing gene function. This method offers a promising alternative to conventional tissue culture-based transformation strategies.

The cultivated peanut (Arachis hypogaea L.) is a main cash crop globally, providing oil, protein, and various beneficial phytochemicals, with high-oleic peanut offering enhanced health benefits and oxidative stability. Despite these advantages, many widely cultivated peanut varieties remain normal-oleic, and the conversion of these varieties to high-oleic types without compromising yield and adaptability is of significant interest. This study evaluated the feasibility of using Pingyangmycin, a chemical mutagen, to induce high-oleic mutations in the popular peanut variety 308 through floral organ injection. The results showed that this method effectively generated high-oleic mutants with oleic acid content exceeding 75%. The mutants yielded more pods and kernels than the parental variety. Genotypic analysis confirmed mutations in the FAD2A and FAD2B genes, associated with the high-oleic phenotype. This novel approach, which reduces seed and reagent requirements and accelerates the breeding timeline, holds promise for enhancing peanut breeding programs and the development of high-oleic cultivars with superior quality and yield.

Peanut web blotch is an important leaf disease caused by Phoma arachidicola, which seriously affects the quality and yield of peanuts. However, the molecular mechanisms of peanut resistance to peanut web blotch are not well understood. In this study, a transcriptome analysis of the interaction between peanut (Arachis hypogaea) and P. arachidicola revealed that total 2989 (779 up- and 2210 down-regulated) genes were all differentially expressed in peanut leaves infected by P. arachidicola at 7, 14, 21 days post inoculation. The pathways that were strongly differentially expressed were the flavone or isoflavone biosynthesis pathways. In addition, two 2-hydroxy isoflavanone synthase genes, IFS1 and IFS2, were strongly induced by P. arachidicola infection. Overexpression of the two genes enhanced resistance to Phytophthora parasitica in Nicotiana benthamiana. Knockout of AhIFS genes in peanut reduced disease resistance to P. arachidicola. These findings demonstrated that AhIFS genes play key roles in peanut resistance to P. arachidicola infection. Promoter analysis of the two AhIFS genes showed several defense-related cis-elements distributed in the promoter region. This study improves our understanding of the molecular mechanisms behind resistance of peanut infection by P. arachidicola, and provides important information that could be used to undertake greater detailed characterization of web blotch resistance genes in peanut.

In July 2022, dieback and discoloration were detected on infected stems of peanut in Qijiang District of Chongqing (106.56°E,29.41°N), China, with an incidence up to 5%. These peanut stems had disease symptoms typical of anthracnose with irregular gray-brown spots with dark brown edges, sunken, and necrotic. High temperature and high humidity were favorable for the growth of the pathogen. To isolate the pathogen, we collected 10 typical infected peanuts and cut one piece from each of symptomatic stems, surface sterilized with 0.5% NaClO for 1 min, and 75% ethanol for 30 s, then rinsed three times with sterile distilled water and dried on sterilized filter paper. These pieces were incubated on potato dextrose agar (PDA) at 25°C in the dark. Pure cultures were obtained from hyphal tips of each colony. It was found that isolates with the same colony morphology were isolated from each infected stem. A representative isolate (L7) was used for morphological characterization, molecular analysis, phylogenetic analysis, and pathogenicity tests. The colonies appeared white to gray, with white margins and aerial hyphae, and the reverse of the colonies was gray to brown. Conidia were cylindrical, aseptate, with obtuse to slightly rounded ends, 13.4 to 18.8 × 4.2 to 5.8 μm (n=50). Morphological characteristics were generally consistent with those of Colletotrichum gloeosporioides species complex (Cannon et al., 2012). For molecular identification, genomic DNA was extracted using a CTAB method and partial sequences of β-tubulin (TUB2), actin (ACT) genes, chitin synthase (CHS) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes were amplified and sequenced using primers T1/T2, ACT-512F/ACT-783R, CHS-79F/CHS-345R, and GDF1/GDR1, respectively (Damm et al., 2012; Dowling et al., 2020). Using the BLAST, TUB2, ACT, CHS and GAPDH gene sequences (GenBank accession No. OR714793, OP168707, OP168708 and OR714794, respectively) were100% (429 bp out of 429 bp), 99.22% (256 bp out of 258 bp), 99.64% (276 bp out of 277 bp) and 100% (253 bp out of 253 bp) identical to C. gloeosporioides CBS:112999 (JQ005587, JQ005500, JQ005326, and JQ005239), respectively. Using Neighbor-Joining algorithm, phylogenetic analysis was conducted based on the concatenated sequences of published TUB2, ACT, CHS and GAPDH genes. The identified isolate (L7) was closely related to C. gloeosporioides. To evaluate pathogenicity, the stems of ten peanut (Zhonghua12) seedlings (2 weeks) were wounded with a sterile toothpick and mycelial plugs (5 mm in diameter) or 20 μl of conidial suspension (105/ml) were inoculated. Non-colonized agar plugs or 20 μl of sterile distilled water were treated as control. After inoculation, the peanuts were kept in a moist chamber at 28°C with 80% humidity in the dark for 24 h, and subsequently transferred to the moist chamber with 12 h light and darkness cycle for 6 days, similar symptoms were observed on all inoculated peanuts. Controls remained asymptomatic. C. gloeosporioides was reisolated from the diseased stems and confirmed using morphological features and sequence analysis of TUB2, ACT, CHS and GAPDH. Anthracnose caused by C. truncatum and C. fructicola has been reported on peanut leaves in China (Gong et al., 2023; Yu et al., 2019). To our knowledge, this is the first report of anthracnose on peanut stem caused by C. gloeosporioides in Chongqing. Our report will provide crucial information for studying on epidemiology and management of this disease.

Peanut root rot, caused by Fusarium spp., is a devastating fungal disease. As part of a program to obtain a biocontrol agent to control peanut root rot in the field, a bacterial strain LY-1 capable of inhibiting the growth of the fungus in vitro was isolated from rhizosphere soil samples collected from wild mint by agar disk dilution and dual-culture assay. Strain LY-1 was identified as Bacillus subtilis based on morphological characteristics, 16S rDNA, and gyrA sequence analyses. The bacterial suspension and cell-free culture filtrate of LY-1 could significantly inhibit the growth of Fusarium oxysporum, Fusarium proliferatum and Fusarium solani, but volatile organic compounds from the cultures had only a weak effect on mycelial growth. The percentage inhibition of 20% concentration of the cell-free culture filtrate of LY-1 on conidium production of each of the three Fusarium species was greater than 72.38%, and the percentage inhibition by the culture filtration on the germination of conidia of the three species was at least 62.37%. The production of extracellular enzyme activity by LY-1 was studied in functional assays, showing protease, cellulase, amylase, chitinase, and β-1,3-glucanase activity, while LY-1 contained a gene encoding iturin, an antifungal lipopeptide. In addition, under pot culture in a greenhouse, culture filtrate of LY-1 significantly promoted the growth of peanut, increasing the fresh and dry mass of the plant by 30.77% and 27.27%, respectively, in comparison with the no-filtrate control. The culture filtrate of LY-1 increased the resistance of peanut plants to F. oxysporum, with the biocontrol efficiency reaching 44.71%. In conclusion, B. subtilis LY-1, a plant-growth-promoting rhizobacterium, was able to protect peanuts from Fusarium spp. infection.

Peanut (Arachis hypogaea L.) is a widely grown oilseed crop of great agricultural importance worldwide. In July 2022, disease symptoms were observed on peanut roots in Laixi (36º85' N, 120º54' E), Shandong Province, China. About 25% of the plants showed various symptoms, including stem and root rot and blackening, microsclerotia on the stem, yellowing and wilting of leaves, and even death. Twenty diseased plants were collected to confirm the pathogen. Symptomatic roots were cut into small pieces, disinfested with 75% ethanol for 1 min and 0.5% NaClO for 2 min, rinsed three times with sterile water, dried on sterile filter paper, and then spread on potato dextrose agar (PDA) supplemented with 100 μg/mL chloramphenicol and incubated at 25°C in the dark. At the beginning of growth, the fungus formed sparse, white mycelia, which white, then darkened with age and microsclerotia were formed in the medium after 5 days. The mycelium aggregated into black, round to oblong or irregularly shaped microsclerotia 84 to 163 μm long and 54 to 125 μm wide (n=40). These morphological characteristics were consistent with the description of Macrophomina phaseolina (Holliday and Punithalingam, 1970). Molecular identification was performed by sequencing the internal transcribed spacer (ITS) region with ITS1 and ITS4 and translation elongation factor 1-alpha (TEF) with EF1-728F/EF1-986R (Glass and Donaldson 1995) of a representative isolate SXY183. ITS (OR056369) and TEF (OR098356) of SXY183 showed 100% and 97.74% similarity with M. phaseolina (KF951622, KF951997), respectively. Phylogenetic analysis was performed using Neighbor-Joining (NJ) analysis based on the gene sequences of ITS and TEF. The fungus was identified as M. phaseolina based on molecular analysis and morphological characteristics. The pathogenicity of a representative isolate (SXY183) was tested on peanuts under greenhouse conditions. Two-week-old peanut (Huayu No. 9115) seedlings were inoculated with a mycelial plug (8 mm diameter) at the root base of each plant and cultured in a greenhouse (30°C during the day and 25°C at night, a 12-h photoperiod, and 80% RH). Ten plants were inoculated with a plug of non-colonized PDA as a control. Brown lesions were observed on the stem and root of all inoculated seedlings 7 days after inoculation, but not on the control plants. The experiment was repeated three times. M. phaseolina was re-isolated from the symptomatic root and confirmed based on morphological characteristics and DNA sequence analysis of ITS and TEF. M. phaseolina is a soil-borne fungus that is distributed worldwide and has a broad host range. Disease agent has previously been reported on several host plants such as adzuki bean, faba bean, watermelon, Plukenetia volubilis, Atractylodes lancea and Curcuma longa in China (Cai et al., 2020; Sun et al. 2016; Sun et al., 2019; Sun et al., 2020; Wang et al., 2020; Wu et al., 2022). However, this is the first report in which M. phaseolina was found to cause peanut root rot in Shandong Province, China. Our report will provide important information for studying the epidemiology and management of this disease.

Peanut (Arachis hypogaea L.) is one of the most economically important crops as a major source of edible oil and protein. In July 2021, a root rot disease was observed on peanut in Laiwu (36º22' N,...