Phytophthora root rot (PRR) is a destructive disease of soybeans (Glycine max (L.) Merr) caused by Phytophthora sojae (P. sojae). The most effective way to prevent the disease is growing resistant or tolerant varieties. Partial resistance provides a more durable resistance against the pathogen compared to complete resistance. Wild soybean (Glycine soja Sieb. & Zucc.) seems to be an extraordinarily important gene pool for soybean improvement due to its high level of genetic variation. In this study, 242 wild soybean germplasms originating from different regions of Heilongjiang province were used to identify resistance genes to P. sojae race 1 using a genome-wide association study (GWAS). A total of nine significant SNPs were detected, repeatedly associated with P. sojae resistance and located on chromosomes 1, 10, 12, 15, 17, 19 and 20. Among them, seven favorable allelic variations associated with P. sojae resistance were evaluated by a t-test. Eight candidate genes were predicted to explore the mechanistic hypotheses of partial resistance, including Glysoja.19G051583, which encodes an LRR receptor-like serine/threonine protein kinase protein, Glysoja.19G051581, which encodes a receptor-like cytosolic serine/threonine protein kinase protein. These findings will provide additional insights into the genetic architecture of P. sojae resistance in a large sample of wild soybeans and P. sojae-resistant breeding through marker-assisted selection.

Wild soybean germplasm is distributed widely in China, particularly in Heilongjiang Province. In this study, 242 wild soybean accessions from four agricultural divisions in Heilongjiang Province were evaluated based on six qualitative and eight quantitative traits. Results showed that a large amount of variation occurred in these evaluated traits. Abundant qualitative traits included the wild type (78.51%), purple flowers (90.50%), needle leaf (39.26%), black seed (83.88%), brown hilum (52.07%), and mud film (87.60). Results of multivariate analysis based on quantitative traits showed that 100-seed weight, seeds weight per plant, number of seeds per plant, number of effective pods, and number of invalid pods were significantly different among samples (p < 0.05). A total of 27 germplasms were screened. Cluster analysis identified the 242 accessions into two groups, not following the geographical distribution pattern, with rich wild soybean resources revealed in the northern site. The present study indicated that wild soybean in Heilongjiang Province should be conserved in situ. The rich genetic diversity revealed in soybeans of different sites in Heilongjiang Province suggested its significant potential utilization in genetic improvement and breakthrough for soybean breeding. This information will help to exploit and conserve wild soybean accessions in Heilongjiang Province.

Sulfur (S) fertilization and rhizobium inoculation are important agronomic practices for improving soybean growth and yield. However, their combined effects on yield components and the resultant impacts on yield need further investigation. Our study aimed to verify the combined effects of S fertilizer and rhizobium inoculant on the yield components and seed yield of soybeans, as well as photosynthesis dynamics during the V5–R6 growth stages. A randomized block design incorporating two factors was employed for field experiments on soybean, involving the application of five rates of sulfur (0, 5.0, 9.8, 14.8, and 19.6 kg S ha⁻¹) with rhizobium inoculation or without. A reduction of 50% in mineral fertilizer according to farmer practice (FP) was applied alongside different rates of sulfur for field experiments on soybeans. The findings indicated that the application of sulfur fertilization significantly enhanced soybean yield by increasing the number of grains per plant (NG) and the number of pods per plant (NP). Maximum grain yield was reached under treatment with an S rate of 19.6 kg S ha⁻¹, which increased NG by 39% more than an S rate of 0 kg S ha⁻¹. Correlation analysis indicated that higher photosynthesis was closely associated with increased yield components. This study demonstrated that applying S fertilizers could improve soybean production by combining the appropriate sulfur concentration and rhizobia inoculation.

Aspartic proteases represent a class of proteolytic enzymes widely implicated in plant growth regulation and abiotic stress responses. Our previous work identified an aspartic protease, GmAP1, whose expression is strongly correlated with flowering time in wild soybean populations. In this study, we further demonstrated that GmAP1 overexpression (OE) significantly delays flowering, whereas CRISPR/Cas9-mediated knockout (CR) accelerates this process. Specifically, OE lines exhibited suppressed expression of CONSTANS (CO) and FLOWERING LOCUS T (FT), along with elevated transcript levels of FLOWERING LOCUS C (FLC). Subcellular localization assays confirmed that GmAP1 is targeted to chloroplasts, where it downregulates the PHD-type transcription factor gene PTM without affecting GOLDEN2-LIKE 1/2 (GLK1/2). Notably, GmAP1 expression was strongly induced by salt stress. GmAP1-OE lines exposed to salt stress showed chlorophyll degradation and reduced net photosynthetic rate (Pn). Both in vivo and in vitro biochemical assays verified that GmAP1 interacts with and degrades the Rubisco large subunit (rbcL), a process correlating with decreased Pn and delayed flowering in OE lines under salt stress. Collectively, our findings reveal that GmAP1 coordinates photosynthetic energy supply and reproductive transition in soybean. Precise modulation of this gene holds substantial practical value for developing early-maturing, salt-tolerant soybean varieties well adapted to saline-alkali environments.