Faba bean (Vicia faba L.) is an important food legume crop, grown for human consumption globally including in China, Turkey, Egypt and Ethiopia. Although genetic gain has been made through conventional selection and breeding efforts, this could be substantially improved through the application of molecular methods. For this, a set of reliable molecular markers representative of the entire genome is required.

Mung bean (Vigna radiata), an essential annual legume, holds substantial value in global agriculture due to its short growth cycle, low input requirements, and nutritional benefits. Despite extensive domestication, the genetic mechanisms underlying its morphological and physiological evolution remain incompletely understood. In this study, we present a gap-free, telomere-to-telomere genome assembly of the mung bean cultivar 'Weilv-9′, achieved through the integration of PacBio HiFi, Oxford Nanopore, and high-throughput chromosome conformation capture (Hi-C) sequencing technologies. The 500-Mb assembly, encompassing 11 chromosomes and containing 28 740 protein-coding genes, reveals that 49.17% of the genome comprises repetitive sequences. Within the genome, we found the recent amplification of transposable elements significantly impacts the expression of nearby genes. Furthermore, integrating structural variation and single-nucleotide polymorphism (SNP) data from resequencing, we identified that the fatty acid synthesis, suberin biosynthetic, and phenylpropanoid metabolic processes have undergone strong selection during domestication. These findings provide valuable insights into the genetic mechanisms driving domestication and offer a foundation for future genetic enhancement and breeding programs in mung beans and related species.

Fusarium wilt (FW), caused by Fusarium oxysporum f. sp. pisi (Fop), has always been an important disease affecting pea production and causing severe yield losses in most pea-growing areas worldwide. Growing resistant pea cultivars is the most economical and effective method for controlling the disease. In this study, firstly, 21 Fusarium oxysporum isolates were identified as races 1 and 5 of Fop based on morphological and molecular characteristics, and the disease reactions of seven pea differential cultivars. Then, a detailed resistance evaluation strategy was established and validated by a death rate score, disease index, and percentage of leaves showing symptoms for each individual plant. Finally, a 1311 pea germplasm collection including 740 accessions from China and 571 accessions aboard or unknown sources was evaluated for resistance to a representative isolate PF22b of Fop race 5, and the results showed that 28 accessions and 164 accessions were highly resistant (HR) and resistant (R), respectively. Among these resistance accessions, 13 HR and 44 R accessions were collected from 19 provinces in China, most of which came from Sichuan, Tibet, and Gansu Provinces. The 15 HR and 120 R accessions were collected in 10 countries outside China or unknown sources, the majority of which came from the United States, Australia, and Russia. The findings would provide important information for using resistance pea cultivars to control Fusarium wilt. Incorporating these resistance accessions into breeding programs will contribute to improving the Fop resistance of pea cultivars.

Endophytic bacteria, especially those that participate in nitrogen fixation, play critical roles in supplying essential nutrients for legume plant growth. Despite that there have been numerous investigations targeting bacterial microbiomes in legume roots and nodules, little is known about embryonic bacteria that facilitate plant nutrient utilization after seed germination. Here, we collected and investigated endophytic bacterial microbiome in edible pea (Pisum sativum) embryos using five representative cultivars and a pea sprout (shoot of pea [SHP]) control. Twenty-six nitrogen-fixing bacteria (NFB) were isolated from pea embryos, with three strains found in fresh grain pea (FGP) and snow pea (SP) exhibiting the strongest nitrogenase activity of above 85 nmol C₂H₄/mL/h. Some NFB isolates are also potassium-solubilizing bacteria (KSB) or phosphorus-solubilizing bacteria (PSB) utilizing inorganic and/or organic phosphorus. All 26 NFB showed variable levels (0.41 to 7.10 μg/mL) of indole-3-acetic acid (IAA) secretion. The nutrient-solubilizing NFB identified in our research are potential targets for biofertilizer development. They could be useful in converting nitrogen, potassium, and/or phosphorus into usable forms for the plants. At the microbiome level, high-throughput 16S ribosomal RNA (rRNA) sequencing of 40 bacterial collections from pea embryos generated 4234 operational taxonomic units (OTUs) using 97% identity as the threshold for clustering high-quality effective reads (valid tags). Analysis of OTU annotation results revealed similar species community structures, abundance, and diversity in most samples. Our embryo-derived endophytic bacterial pool provides a microbiome platform for seed dormancy and germination research of edible peas, as well as for digging new biofertilizer resources in general.

Although the pod color was one of the seven characteristics Mendel studied in peas, the mechanism of color variation in peas with purple pods has not been reported. This study systemically analyzed the difference between two pea accessions with green pods (GPs) and purple pods (PPs) at two pod developmental stages from the metabolome and transcriptome levels, aiming to preliminarily explore the mechanism and of color variation in PPs and screen out the candidate genes. A total of 180 differentially accumulated metabolites (DAMs) belonged to seven flavonoid subgroups and 23 flavonoid-related differentially expressed genes (DEGs) were identified from the analysis of the KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment, respectively. Among the 180 flavonoid metabolites, ten anthocyanin compounds, which were the principal pigments in PPs and might be the major reason for the purple color formation, were significantly up-accumulated in both of the different pod development stages of PPs. A transcriptome analysis revealed that eight genes encoding enzymes (C4H, CHI, F3H, F3’H, F3’5’H, DFR, ANS, and FLS) involved in the flavonoid synthesis pathway were significantly upregulated in PPs and finally resulted in the significant accumulation of flavonoid and anthocyanin metabolites. The joint analysis of two omics and a weighted gene co-expression network analysis (WGCNA) also screened out that the WD-40 protein-encoding gene, one WRKY and three MYB transcription factor genes exhibited significant upregulation in PPs, and highly correlated with several structural genes in flavonoid synthesis pathways, indicating that these genes are involved in the regulation of pod color formation in PPs. Overall, the results of this study first explored the mechanism underlying the purple color variation between PPs and GPs, and then preliminarily screened out some candidate genes responsible for the pod color formation in PPs.