SUMMARY: The soybean Rpp1 locus confers resistance to Phakopsora pachyrhizi, causal agent of rust, and resistance is usually dominant over susceptibility. However, dominance of Rpp1‐mediated resistance is lost when a resistant genotype (Rpp1 or Rpp1b) is crossed with susceptible line TMG06_0011, and the mechanism of this dominant susceptibility (DS) is unknown. Sequencing the Rpp1 region reveals that the TMG06_0011 Rpp1 locus has a single nucleotide‐binding site leucine‐rich repeat (NBS‐LRR) gene (DS‐R), whereas resistant PI 594760B (Rpp1b) is similar to PI 200492 (Rpp1) and has three NBS‐LRR resistance gene candidates. Evidence that DS‐R is the cause of DS was reflected in virus‐induced gene silencing of DS‐R in Rpp1b/DS‐R or Rpp1/DS‐R heterozygous plants with resistance partially restored. In heterozygous Rpp1b/DS‐R plants, expression of Rpp1b candidate genes was not significantly altered, indicating no effect of DS‐R on transcription. Physical interaction of the DS‐R protein with candidate Rpp1b resistance proteins was supported by yeast two‐hybrid studies and in silico modeling. Thus, we conclude that suppression of resistance most likely does not occur at the transcript level, but instead probably at the protein level, possibly with Rpp1 function inhibited by binding to the DS‐R protein. The DS‐R gene was found in other soybean lines, with an estimated allele frequency of 6% in a diverse population, and also found in wild soybean (Glycine soja). The identification of a dominant susceptible NBS‐LRR gene provides insight into the behavior of NBS‐LRR proteins and serves as a reminder to breeders that the dominance of an R gene can be influenced by a susceptibility allele.

The role of a soybean 14-3-3 gene ( Glyma05g29080) in defense against white mold and in nodulation was investigated by loss-of-gene-function with CRISPR-Cas9 editing and silencing of RNA interference (RNAi). Particle bombardment was used to introduce the CRISPR expression cassette to target the soybean 14-3-3 gene and an RNAi construct to silence gene transcription. Transmission of the edited 14-3-3 gene and the RNAi construct was confirmed in their respective progeny. The recovered transgenic plants and their progeny were significantly more susceptible to Sclerotinia sclerotiorum infection and showed a significant reduction in nodulation, thus confirming the role of the 14-3-3 gene ( Glyma05g29080) in both nodulation and defense.

Summary: Oxalate oxidases ( OxO ) catalyse the degradation of oxalic acid ( OA ). Highly resistant transgenic soybean carrying an OxO gene and its susceptible parent soybean line, AC C olibri, were tested for genome‐wide gene expression in response to the necrotrophic, OA ‐producing pathogen S clerotinia sclerotiorum using soybean cDNA microarrays. The genes with changed expression at statistically significant levels (overall F ‐test P ‐value cut‐off of 0.0001) were classified into functional categories and pathways, and were analysed to evaluate the differences in transcriptome profiles. Although many genes and pathways were found to be similarly activated or repressed in both genotypes after inoculation with S . sclerotiorum , the OxO genotype displayed a measurably faster induction of basal defence responses, as observed by the differential changes in defence‐related and secondary metabolite genes compared with its susceptible parent AC C olibri. In addition, the experiment presented provides data on several other transcripts that support the hypothesis that S . sclerotiorum at least partially elicits the hypersensitive response, induces lignin synthesis (cinnamoyl CoA reductase) and elicits as yet unstudied signalling pathways ( G ‐protein‐coupled receptor and related). Of the nine genes showing the most extreme opposite directions of expression between genotypes, eight were related to photosynthesis and/or oxidation, highlighting the importance of redox in the control of this pathogen.

In Brazil, some of the most important insect pests causing damage to soybean (Glycine max) are stink bugs. Soybean production would increase if varieties with enhanced resistance were developed. The aim of this work was to examine different traits associated with plant development, and yield-related traits, in an F_2:3 soybean population in a stink bug-infested field and to evaluate genetic parameters and correlations among those traits. The parents and progeny from 229 F₂ plants developed by crossing a resistant cultivar (IAC-100) with a susceptible cultivar (CD-215) were evaluated in three replications in a single environment. Seven agronomic traits and eight indicators of insect resistance were measured. Genotypes showed significant differences for all traits except lodging. The grain-filling period exhibited a positive genotypic correlation of 0.66 with hundred-seed weight, whereas a negative genotypic correlation of −0.53 was found between pod damage index (%) and weight of healthy seeds. In general, a shorter pod-filling period, lower weight of hundred-seeds, lower indices of pod damage, and higher seed-yield per plant were phenotypic traits of genotypes resistant to these insects.

This strategic plan summarizes the major accomplishments achieved in the last quinquennial by the soybean [ Glycine max (L.) Merr.] genetics and genomics research community and outlines key priorities for the next 5 years (2024–2028). This work is the result of deliberations among over 50 soybean researchers during a 2‐day workshop in St Louis, MO, USA, at the end of 2022. The plan is divided into seven traditional areas/disciplines: Breeding, Biotic Interactions, Physiology and Abiotic Stress, Functional Genomics, Biotechnology, Genomic Resources and Datasets, and Computational Resources. One additional section was added, Training the Next Generation of Soybean Researchers, when it was identified as a pressing issue during the workshop. This installment of the soybean genomics strategic plan provides a snapshot of recent progress while looking at future goals that will improve resources and enable innovation among the community of basic and applied soybean researchers. We hope that this work will inform our community and increase support for soybean research.

In July 2024, soybean (Glycine max) with symptoms of red crown rot, caused by Calonectria ilicicola, were observed in a commercial field with a history of corn-soybean rotation in Marion County, Missouri. Soybean were planted on May 12 and foliar symptoms including interveinal chlorosis and premature senescence, were visible on plants at the R3 growth stage with incidence estimated at 5% of the field. Reddish coloration was observed on the lower stem of symptomatic plants, along with reddish-orange globular perithecia measuring 300-500 µm in height and 250-350 µm in diameter, typical of C. ilicicola infection. Twelve symptomatic plants were collected, and stems were cleaned, followed by immersion in 70% ethanol for 30 seconds, 1.25% NaOCl for 5 minutes, and rinsing three times. Surface disinfected stems were dried at 24°C. After 24 hours, stems were split and placed on water agar (WA) amended with 1% penicillin-streptomycin solution (P4333; Sigma Aldrich). After 4 to 5 days, conidiophores characteristic of C. ilicicola, were observed. Conidia from nine stems were transferred to WA and serial transfers of conidia were made until pure single spore cultures of isolates were obtained and transferred to potato dextrose agar (PDA). On WA, the isolates produced hyaline mycelium that developed conidiophores and conidia as well as reddish brown chlamydospores. Single spore isolates transferred to PDA produced fluffy white mycelium that turned reddish. Three isolates were used for DNA extraction with the Zymo DNA extraction kit (ZD6005). Parts of the internal transcriber region (ITS) (ITS-F2: 5'-TTTACAACTCCCAAACCCCATGTGAAC-3'and ITS-R2: 5'-CTACCTGATTCGAGGTCAA CCAGAA-3') histone 3 (HIS3) (Crous et al. 2004), translation elongation 1α (EF1α) (Carbone and Kohn 1999; O'Donnell et al. 1998) and β-tubulin (TUB2) (Crous et al. 2004; O'Donnell and Cigelnik 1997) genes were amplified and their DNA sequenced. Sequences were processed in Geneious Prime 2024.0 and deposited at NCBI GenBank under the accession numbers PQ390253, PQ390254 and PQ390255 (ITS), PQ519580, PQ519581 and PQ519582 (HIS3), PQ507479, PQ507480 and PQ507481 (EF1α) and PV092563, PV092564 and PV092565 (TUB2). These DNA sequences show 100% identity to C. ilicicola sequences. To fulfill Koch's postulates, eight pots containing three plants (cultivar Williams 82) each were grown for two weeks in a growth chamber at 26°C with a 14-hour photoperiod and watered daily. Six pots were inoculated with 4 mm plugs of mycelium from the distal growing edge of the fungal isolate on PDA plates. The other two pots, treated with 4 mm plugs of PDA-only, served as negative controls. The planting medium at the base of each plant was gently removed, and inoculum was placed on the primary root, approximately 7 mm below the soil level. Five days after inoculation, plants started exhibiting reddish/blackish discoloration at the base of the stems, typical of red crown rot. Then, C. ilicicola was re-isolated from symptomatic plants three weeks post-inoculation and identified by conidial morphology. Together, these results confirmed the presence of C. ilicicola in Marion County, Missouri. Although C. ilicicola was first confirmed in the United States in 1965 on peanuts, it has gained renewed interest due to its presence in commercial soybean production, where symptoms can resemble sudden death syndrome. The pathogen poses a significant threat to >2,000,000 ha of soybean and approximately 8,000 ha of peanut grown in Missouri.