Two-Pass Weed Management with Preemergence and Postemergence Herbicides in Glyphosate-Resistant Soybean

There is little information on the efficacy and profitability of two-pass weed control strategies in soybean when a preemergence (PRE) residual herbicide is followed by glyphosate applied late postemergence (LPOST) under Ontario, Canada environmental conditions. Ten field trials were conducted during 2011-2013 in Ontario, Canada to determine the level of weed control, yield and net returns of various preemergence/postemergence programs in glyphosate-resistant soybean. Crop injury was 2% or less with the herbicides evaluated except for chlorimuron + flumioxazin (PRE) and pyroxasulfone + flumioxazin (PRE) which caused 4% and 7% visible injury in soybean, respectively. A single application of glyphosate resulted in variable weed control (73% - 98%) while the sequential application of glyphosate provided excellent weed control (98% - 100%). The control of all weeds 8 WAA after the LPOST glyphosate application was equivalent regardless of the PRE herbicide applied (96% - 100%). Soybean yield was equivalent to the weed free control regardless of the PRE herbicide applied. Soybean yield was lower than the sequential application of glyphosate with chlorimuron or pyroxasulfone/flumioxazin PRE fb glyphosate LPOST. Generally net return with the two-pass programs was equivalent to the sequential application of glyphosate. Net returns were lower than the sequential application of glyphosate with chlorimuron or s-metolachlor + flumetsulam followed by glyphosate LPOST. Based on these results, a sequential application of glyphosate or a two-pass program of a preemergence residual herbicide followed by glyphosate LPOST are the preferred weed management programs in glyphosate-resistant soybean. The two-pass programs have the potential to reduce selection pressure for glyphosate-resistant weeds.

Influence of Herbicides on Competition Weed and Glyphosate-resistant Soybean

Competitions of light,nutrient and water between transgenic glyphosate resistant soybean and weed were evaluated with different herbicides(glyphosate,acetochlor,and the mixture of fomesafen and quizalofop-p-ethyl)in filed,which displayed that the application of the mixture of fomesafen and quizalofop-p-ethyl on soybeans had the best anti-herbicidal effect while glyphosate had the weakest effect.The half-life extended by herbicide mixture would affect the soil nutrients.Weed-soybean competitions affected the absorption of nutrients on soybean and yield.However,effective control of weeds could significantly reduce the weed density,improve the field through different layers of light transmittance and the absorption of nutrients on soybean,and enhance the comprehensive competitiveness of soybean.

Late-Season Grass Weed Management with In-Crop and Post-Harvest Herbicides in Twin-Row Glyphosate-Resistant Soybean

Emergence of grasses late in the season has become a problem in glyphosate-resistant (GR) soybean production in the southern US. A 3-yr field study was conducted from 2011 to 2013 at Stoneville, MS to determine efficacy of post-harvest and pyroxasulfone-based in-crop herbicides on late-season grasses and yield in twin-row glyphosate-resistant soybean. Experiments were conducted in a split-plot arrangement of treatments in a randomized complete block design with fall herbicides (with and without pendimethalin at 1.12 kg ai ha-1 and paraquatat 0.84 kg ai ha-1) as main plots and in-crop herbicides as subplots with four replications. The six in-crop herbicide programs were: glyphosate applied early postemergence (EPOST) at 0.84 kg·aeha-1 followed by (fb) glyphosate late postemergence (LPOST) at 0.84 kg·ha-1 with and without pyroxasulfone preemergence (PRE) applied at 0.18 kg ai ha-1, pyroxasulfone PRE fb glyphosate at 0.84 kg·ha-1 LPOST or glyphosate at 0.84 kg·ha-1 + S-metolachlor at 1.68 kg ai ha-1 EPOST, pyroxasulfone PRE fb S-meto- lachlor at 1.12 kg·ha-1 + fomesafen at 0.27 kg ai ha-1 EPOST fb clethodim at 0.14 kg ai ha-1, and a no-herbicide control. Browntop millet, Digitaria spp., and junglerice densities at 2 weeks after LPOST, grass weed dry biomass at harvest, and soybean yield were similar regardless of post- harvest herbicides in all three years. At 2 weeks after LPOST, browntop millet, Digitaria spp. and junglerice densities were greatly reduced in all five in-crop herbicide treatments compared with no herbicide plot in all three years. Grass weed dry biomass in no-herbicide plots was 3346, 6136, and 6916 kg·ha-1 in 2011, 2012, and 2013, respectively and the five herbicide treatments reduced grass weed dry biomass by at least 87%, 84%, and 99% in 2011, 2012, and 2013, respectively. Soybean yield was higher with all five in-crop herbicide treatments compared to no herbicide control in all three years. These results indicate that browntop millet, Digitaria spp., and junglerice infestations can be reduced with pyroxasulfone-based in-crop herbicide programs in twin-row GR soybean.

Control of Glyphosate-Resistant Waterhemp with Two-Pass Weed Control Strategies in Glyphosate/Dicamba-Resistant Soybean

Waterhemp is a small-seeded, dioecious, broadleaf weed that emerges throughout the growing season. If left uncontrolled, waterhemp interference can reduce soybean yield up to 73%. Glyphosate-resistant (GR) waterhemp was first discovered in one county in Ontario in 2014;as of 2017, it has been found in two other counties. Glyphosate/dicamba-resistant soybean can be sprayed with glyphosate and/or dicamba preplant (PP), preemergence (PRE) and/or postemergence (POST). The objective of this study was to determine the control of GR waterhemp in glyphosate/dicamba-resistant soybean with PRE residual herbicides, glyphosate/dicamba applied POST or a two-pass program of a PRE residual herbicide followed by glyphosate/dicamba applied POST. At 8 weeks after application (WAA), pyroxasulfone (150 g ai ha-1), S-metolachlor/metribuzin (1943 g ai ha-1), pyroxasulfone/sulfentrazone (300 g ai ha-1) and flumioxazin/pyroxasulfone (240 g ai ha-1), applied PRE, resulted in 71%, 85%, 82% and 90% GR waterhemp control, respectively. The same PRE herbicides, followed by glyphosate/dicamba (1800 g ae ha-1) POST, improved control to greater than 96%. This study concludes that a two-pass program of an effective soil applied residual herbicide followed by glyphosate/dicamba POST controlled GR waterhemp in glyphosate/dicamba-resistant soybean.

Linuron Biologically Effective Dose for Glyphosate-Resistant Giant Ragweed (<i>Ambrosia trifida</i>L.) Control in Soybean (<i>Glycine max</i>L.)

Glyphosate-resistant (GR) giant ragweed (Ambrosia trifida L.) was first identified in Canada in 2008 and has since been found throughout southwestern Ontario. Six field trials were conducted over a two-year period (2012, 2013) on Ontario farms with GR giant ragweed to evaluate the efficacy of linuron applied pre-plant (PP) in soybean (Glycine max (L.) Merr.). The dose required for 50%, 80%, and 95% GR giant ragweed control was 1238, 2959, and 6018 g·ai·ha-1 four weeks after application (WAA), respectively. The linuron dose needed for 50%, 80%, and 95% reduction in density was 1554, 3181, and 5643 g·ai·ha-1 and 1204, 2496, and 4452 g·ai·ha-1 for dry weight, respectively. Application of 7874 g·ai·ha-1 linuron was needed to obtain soybean yields that were 90% of the weed-free control;approximately 3.5 times the maximum field recommended dose. To achieve 95% and 98% yields, greater than 8640 g·ai·ha-1 linuron was required. Application of linuron plus glyphosate PP in soybean will help to control GR giant ragweed as well as reduce GR selection pressure.

Development of Transgenic Glyphosate-Resistant Rice with G6 Gene Encoding 5-Enolpyruvylshikimate-3-Phosphate Synthase

Glyphosate-resistant crops have been a huge economic success for genetic engineering. The creating of new glypbosateresistant plants would increase the available choices for planting and lower the price of genetically modified crop seeds. A novel G6 gene from Pseudomonas putida that encoded 5-enolpyruvylshikimate-3-phosphate synthase （EPSPS） was previously isolated. The G6 gene was transfected into rice via Agrobacterium-mediated transformation. The transgenic rice obtained was confirmed by PCR, Southern, and Western blots. The lab experiment and field trials further confirmed that the transgenic rice can survive glyphosate spraying at a dose of 8 g L^-1. In contrast, conventional rice was killed at a weed control glyphosate spray dose of 1 g L^-1. Altogether, the present study showed that the G6 gene works well in rice in vivo for glyphosate-resistance.

Control of Glyphosate-Resistant Giant Ragweed (Ambrosia trifida L.) with Isoxaflutole and Metribuzin Tankmix

Five field trials were conducted over a two-year period (2013, 2014) to determine the control of glyphosate-resistant (GR) giant ragweed with isoxaflutole (IFT) and metribuzin (MTZ) applied alone and in combination. Treatments were designed to assess the dose response of an IFT plus MTZ tank-mix as well as each chemical applied alone to classify the response using Flint’s adaptation of Colby’s equation. Two factor factorial experiments were performed in the growth room to ascertain the response of IFT versus glyphosate, IFT versus MTZ, and IFT plus MTZ versus glyphosate on single plants. Field experiments evaluated the control of GR giant ragweed with IFT plus MTZ in tank-mix in a 1:4 ratio. The rate of IFT plus MTZ for 80% control of GR giant ragweed at 4 and 8 weeks after application (WAA) was 518 (104 g a.i. ha-1 IFT + 414 g a.i. ha-1 MTZ) and 631 g a.i. ha-1 (126 g a.i. ha-1 IFT + 505 g a.i. ha-1 MTZ), respectively. A rate of 668 and 467 g a.i. ha-1 was required to reduce GR giant ragweed density and biomass by 80%, respectively. Field experiments evaluating the control of GR giant ragweed with tank-mixes of IFT plus MTZ, where glyphosate was a constant tank-mix partner, were mostly synergistic. However, the low tank-mix rate (52.5 + 210 g a.i. ha-1) had an additive response for GR giant ragweed biomass reduction. When tested in the greenhouse and growth room, glyphosate susceptible (GS) giant ragweed showed some antagonism with glyphosate and isoxaflutole tank-mixes at rates less than commercial field rates. GR giant ragweed showed an additive response across all treatments in the growth room. Greenhouse experiments evaluating IFT versus MTZ and IFT plus MTZ versus glyphosate revealed all tank-mix treatments to be synergistic at 2 WAA.

Glyphosate-Resistant Giant Ragweed(Ambrosia trifida L.)in Ontario:Dose Response and Control with Postemergence Herbicides

Giant ragweed (Ambrosia trifida L.) is competitive with agronomic crops and can cause significant yield losses. Rapid adoption of glyphosate-resistant (GR) crops and a concomitant increase in the reliance on glyphosate for weed management has led to the evolution of GR giant ragweed in Ontario, Canada. Field studies were conducted to evaluate the level of resistance in giant ragweed biotypes from Ontario, and to evaluate the effectiveness of various postemer-gence (POST) herbicides in soybean (Glycine max L.). The effective dose (ED) to provide 50%, 80% and 95% giant ragweed control was up to 1658, 9991 and >43200 g?a.e.?ha–1 4 weeks after application (WAA), respectively. For effective control, growers would need to apply glyphosate 18 times greater than the recommended field application dose. Glyphosate applied at the recommended field dose of 900 g?a.e.?ha–1 provided up to 57% control and resulted in soybean yield equivalent to the weedy check. Cloransulam-methyl applied POST provided up to 99% control, reduced giant ragweed density 98%, reduced giant ragweed shoot dry weight 99% and resulted in soybean yield equivalent to the weedfree check. Chlorimuron-ethyl, fomesafen, imazethapyr and imazethapyr plus bentazon applied alone or with glyphosate did not provide adequate control of GR giant ragweed. Based on these results, some GR giant ragweed biotypes from Ontario have evolved a high level of resistance to glyphosate. Cloransulam-methyl applied POST was the only herbicide that provided adequate control and suggests that additional weed management tactics will need to be implemented in order to effectively manage GR giant ragweed.

Efficacy of POST glyphosate applications in combination with other POST herbicides in glyphosate-resistant corn (Zea mays L.)

The use of glyphosate-resistant corn has facilitated a shift from a reliance on preemergence residual herbicides to postemergence (POST) herbicides, and in some cases exclusively glyphosate. Glyphosate is a non-selective herbicide that is relatively slow-acting, which may allow weeds to continue to compete with corn after application and potentially decrease crop yield. The addition of several POST corn herbicides, with some residual control, to an early-season glyphosate application was examined to determine if the tankmix combination would improve the speed of weed control compared to glyphosate applied alone. Seven field trials were conducted over three years (2009, 2010 and 2011) near Ridgetown and Exeter, Ontario. The control of common ragweed was improved 3 days after application (DAA) with three POST glyphosate tankmixes compared to glyphosate alone. However control was still less than 55%. Depending on the weed species examined, at 28 DAA two of the glyphosate tankmix treatments tested provided better common ragweed, common lambsquarters, or green foxtail control than glyphosate alone. Treatments providing better weed control at 28 DAA also typically decreased weed density compared to glyphosate alone.

Preplant and Postemergence Control of Glyphosate-Resistant Giant Ragweed in Corn

Glyphosate-resistant (GR) giant ragweed has recently been identified in southwestern Ontario and has the potential to be a significant problem for regional corn producers. Eight field trials [four with preplant (PP) and four with postemergence (POST) herbicides] were conducted from 2013 to 2014 on various Ontario farms infested with GR giant ragweed to determine the efficacy of PP and POST tank-mixes in corn. Glyphosate tank-mixed with atrazine, dicamba, dicamba/atrazine, mesotrione plus atrazine, flumetsulam, isoxaflutole plus atrazine, saflufenacil/dimethenamid-P, S-metolachlor/atrazine and rimsulfuron applied PP provided up to 54%, 95%, 93%, 95%, 40%, 89%, 91%, 50% and 93% control of GR giant ragweed and reduced dry weight 69%, 100%, 99%, 100%, 30%, 92%, 98%, 66% and 99%, respectively. POST application of glyphosate alone and tank-mixed with 2,4-D ester, atrazine, dicamba, dicamba/diflufenzopyr, dicamba/atrazine, bromoxynil plus atrazine, prosulfuron plus dicamba, mesotrione plus atrazine, topramezone plus atrazine, tembotrione/thiencarbazone-methyl and glufosinate provided up to 31%, 84%, 39%, 94%, 89%, 86%, 83%, 78%, 72%, 43%, 63% and 58% GR giant ragweed and reduced dry weight 55%, 99%, 72%, 99%, 99%, 98%, 96%, 96%, 93%, 89%, 91% and 95%, respectively. In general, PP control of GR giant ragweed was greater than POST applied herbicides evaluated. Based on these results, glyphosate tank-mixes containing dicamba or mesotrione plus atrazine applied PP, and dicamba applied POST will provide the most consistent control of GR giant ragweed in corn.

GmSTF accumulation mediated by DELLA protein GmRGAs contributes to coordinating light and gibberellin signaling to reduce plant height in soybean

Plant height influences plant architecture,lodging resistance,and yield performance.It is modulated by gibberellic acid(GA)metabolism and signaling.DELLA proteins,acting as central repressors of GA signaling,integrate various environmental and hormonal signals to regulate plant growth and development in Arabidopsis.We examined the role of two DELLA proteins,GmRGAa and GmRGAb,in soybean plant height control.Knockout of these proteins led to longer internodes and increased plant height,primarily by increasing cell elongation.GmRGAs functioned under different light conditions,including red,blue,and far-red light,to repress plant height.Interaction studies revealed that GmRGAs interacted with the blue light receptor GmCRY1b.Consistent with this,GmCRY1b partially regulated plant height via GmRGAs.Additionally,DELLA proteins were found to stabilize the protein GmSTF1/2,a key positive regulator of photomorphogenesis.This stabilization led to increased transcription of GmGA2ox-7b and subsequent reduction in plant height.This study enhances our understanding of DELLA-mediated plant height control,offering Gmrgaab mutants for soybean structure and yield optimization.

Identification and fine mapping of qSW2 for leaf slow wilting in soybean

Drought is one of the abiotic stresses limiting the production of soybean(Glycine max).Elucidation of the genetic and molecular basis of the slow-wilting(SW)trait of this crop offers the prospect of its genetic improvement.A panel of 188 accessions and a set of recombinant inbred lines produced from a cross between cultivars Liaodou 14 and Liaodou 21 were used to identify quantitative-trait loci(QTL)associated with SW.Plants were genotyped by Specific-locus amplified fragment sequencing and seedling leaf wilting was assessed under three water-stress treatments.A genome-wide association study identified 26 SW-associated single-nucleotide polymorphisms(SNPs),including three located in a 248-kb linkage-disequilibrium(LD)block on chromosome 2.Linkage mapping revealed a major-effect QTL,qSW2,associated with all three treatments and adjacent to the LD block.Fine mapping in a BC_(2)F_(3) population derived from a backcross between Liaodou 21 and R26 confined qSW2 to a 60-kb interval.Gene expression and sequence variation analysis identified the gene Glyma.02 g218100,encoding an auxin transcription factor,as a candidate gene for qSW2.Our results will contribute significantly to improving drought-resistant soybean cultivars by providing genetic information and resources.

Emulsifying property,antioxidant activity,and bitterness of soybean protein isolate hydrolysate obtained by Corolase PP under high hydrostatic pressure

Enzymatic hydrolysis of proteins can enhance their emulsifying properties and antioxidant activities.However,the problem related to the hydrolysis of proteins was the generation of the bitter taste.Recently,high hydrostatic pressure(HHP)treatment has attracted much interest and has been used in several studies on protein modification.Hence,the study aimed to investigate the effects of enzymatic hydrolysis by Corolase PP under different pressure treatments(0.1,100,200,and 300 MPa for 1-5 h at 50℃)on the emulsifying property,antioxidant activity,and bitterness of soybean protein isolate hydrolysate(SPIH).As observed,the hydrolysate obtained at 200 MPa for 4 h had the highest emulsifying activity index(47.49 m^(2)/g)and emulsifying stability index(92.98%),and it had higher antioxidant activities(44.77%DPPH free radical scavenging activity,31.12%superoxide anion radical scavenging activity,and 61.50%copper ion chelating activity).At the same time,the enhancement of emulsion stability was related to the increase of zeta potential and the decrease of mean particle size.In addition,the hydrolysate obtained at 200 MPa for 4 h had a lower bitterness value and showed better palatability.This study has a broad application prospect in developing food ingredients and healthy foods.

Glyphosate-Resistant Common Ragweed Control in Corn with Postemergence Herbicides

Four field trials were conducted on a farm infested with glyphosate-resistant (GR) common ragweed during 2016 and 2017 to evaluate various postemergence (POST) herbicides for the control of GR common ragweed in GR corn. Dicamba at 600 g·a.i.·ha-1, dicamba/diflufenzopyr at 200 g·a.i.·ha-1, dicamba/atrazine at 1500 g·a.i.·ha-1, topramezone + atrazine at 12.5 + 500 g·a.i.·ha-1, bromoxynil + atrazine at 280 + 1500 g·a.i.·ha-1, glufosinate at 500 g·a.i.·ha-1 and 2,4-D ester at 560 g·a.i.·ha-1 provided 58% to 85% control at 4 WAA and 49% to 88% control at 8 WAA. Other herbicides evaluated controlled GR common ragweed 9% to 41%. Common ragweed density was reduced 97%, 95%, 95% and 87% and shoot dry weight was reduced 93%, 95%, 94% and 90% with bromoxynil + atrazine, dicamba, glufosinate and topramezone + atrazine applied POST in GR corn, respectively. Results show that dicamba, bromoxynil + atrazine, topramezone + atrazine and glufosinate applied POST are the most efficacious herbicides among the herbicides evaluated for the control of GR common ragweed in GR corn.

Susceptible and Glyphosate-Resistant Palmer Amaranth (<i>Amaranthus palmeri</i>) Response to Glyphosate Using C¹⁴as a Tracer: Retention, Uptake, and Translocation

The foliar retention, absorption, translocation, and diffusion of glyphosate in glyphosate resistant-(R) and susceptible (S)-Palmer amaranth populations from seed collected in Georgia in 2007 were examined. The R population of Palmer amaranth had an elevated copy number of the EPSPS gene conferring the mechanism of resistance. When applications of 14C-glyphosate to a single leaf followed entire plant treatment with glyphosate, the distribution percentages were similar for R and S for the above and below treated leaves when harvested at 1, 6, 12, 24, and 48 hours after treatment (HAT). There were initially no differences between R and S at 1 HAT with an average of 8% absorption for both biotypes. However, data indicated that glyphosate absorption increased for R-Palmer amaranth reaching 41% within 6 HAT and was significantly different (P = 0.01) from the 28% absorbed by S-Palmer amaranth. Glyphosate resistant and susceptible Palmer amaranth averaged 44% 14C-glyphosate absorption by 24 HAT. There were no differences for 14C-glyphosate Bq/mg of plant tissue between R and S for the above the treated leaf and below the treated leaf portions of plants at 1, 6, 12, 24, or 48 HAT. However, root accumulation of 14C-glyphosate in plant tissue was significantly greater by 12 HAT for the roots of R (1.21 Bq/mg) than for S (0.51 Bq/mg). The treated leaf of the R-Palmer amaranth plants exhibited greater translocation of 14C-glyphosate in Bq/mg of tissue than the susceptible over time, indicating no detrimental effect or cost of fitness due to EPSPS gene amplification. Additionally, there were no differences in glyphosate retention in leaf discs assays between R and S biotypes. In spite of an average of 6.5 Bq efflux out of R and S leaf discs after 15 minute, only 0.4 Bq was retained after 150 minutes. Glyphosate was not retained over time in the leaf discs for R and S, and there were no biotype differences within bathing times. However, the rate of efflux (the slope of the curves) was greater for the R biotype. These data support the reported gene amplification non-target site glyphosate resistance mechanism in Palmer amaranth.

Influence of late emerging weeds in glyphosate-resistant corn

Fifteen field trials were conducted from 2009 to 2011 in Ontario, Canada and Michigan, USA to determine how long glyphosate-resistant corn needs to be kept weed-free after emergence to prevent yield loss. Data were separated into two environments based on when yield loss first occurred after glyphosate application. In Environment 1 (4/15 sites) yield was not reduced when corn was kept weed-free until the 4-leaf stage. However, in Environment 2 (11/15 sites) there was no yield loss when corn was kept weed-free up to the 2-leaf stage. The most prominent weeds were velvetleaf, redroot pigweed, common ragweed, common lambsquarters and foxtail species. While later emerging weeds did not necessarily impact corn yield, weeds emerging after the 2- and 4-leaf corn stage likely produced seed that was added to the soil seed bank. Weeds emerging after 6-, 8-, and 10-leaf corn growth stages were small (low biomass/seedlings) and most likely did not reach reproductive maturity. Based on this research, corn must be maintained weed-free up to the 4-leaf stage. Any weeds emerging after that did not influence corn yield.

CRISPR/CasRx-mediated resistance to Soybean mosaic virus in soybean

Soybean mosaic virus(SMV),an RNA virus,is the most common and destructive pathogenic virus in soybean fields.The newly developed CRISPR/Cas immune system has provided a novel strategy for improving plant resistance to viruses;hence,this study aimed to engineer SMV resistance in soybean using this system.Specifically,multiple sgRNAs were designed to target positive-and/or negative-sense strands of the SMV HC-Pro gene.Subsequently,the corresponding CRISPR/CasRx vectors were constructed and transformed into soybeans.After inoculation with SMV,39.02%,35.77%,and 18.70%of T_(1)plants were confirmed to be highly resistant(HR),resistant(R),and mildly resistant(MR)to SMV,respectively,whereas only 6.50%were identified as susceptible(S).Additionally,qRT-PCR and DAS-ELISA showed that,both at 15 and 30 d post-inoculation(dpi),SMV accumulation significantly decreased or was even undetectable in HR and R plants,followed by MR and S plants.Additionally,the expression level of the CasRx gene varied in almost all T_(1)plants with different resistance level,both at 15 and 30 dpi.Furthermore,when SMV resistance was evaluated in the T_(2)generation,the results were similar to those recorded for the T_(1)generation.These findings provide new insights into the application of the CRISPR/CasRx system for soybean improvement and offer a promising alternative strategy for breeding for resistance to biotic stress that will contribute to the development of SMV-immune soybean germplasm to accelerate progress towards greater soybean crop productivity.

Assessing the Efficacy of Wheat-Soybean Based Intercropping System at Different Plant Densities in Bambili, Cameroon

Wheat is one of the most important cereals in the world, serving as a staple for millions globally. In the wake of the geopolitical crisis between Russia and Ukraine, it has become incumbent for many countries to invest in wheat production. Improving cropping systems for wheat production is paramount. Intercropping cereals with legumes has tremendous advantages. Therefore, this study was designed to optimize wheat production by intercropping it with soybean at different densities. Between March and August 2023, a randomized complete block design trial was conducted in Bambili, North West of Cameroon with treatments T1 (wheat monocrop at 200,000 plants ha−1), T2 (soybean monocrop at 250,000 plants ha−1), T3 (200,000 wheat and 125,000 soybean ha−1), T4 (100,000 wheat and 250,000 soybean ha−1), T5 (200,000 wheat and 250,000 soybean ha−1) and T6 (100,000 wheat and 125,000 soybean ha−1). Results revealed that growth parameters of wheat were not significantly influenced by monocrop or intercrop. The yield of wheat was significantly higher in the monocrop than the intercrop treatments, with slight variation amongst the intercrop treatments. Soybean yield was higher in the monocrop than in the intercrop, with no variations amongst the intercrop treatments. Only the land equivalence ratio (LER) for T5 was greater than 1.0. The competitive ratio for T5 was 0.54 for wheat and 1.90 for soybean, comparatively lower than the other monocrop treatments. Intercropping wheat and soybean at 200,000:250,000 ratio is recommended.

Identification of Rhizobia Isolated from Nodules of Mexican Commercial Soybean Varieties

Rhizobia, crucial for nitrogen fixation in leguminous plants, play a vital role in soybean cultivation. This study, conducted in Mexico, a major soybean importer, aimed to identify bacteria from nodules of five soybean varieties in high-production regions. Multilocus sequence analysis (MLSA) was employed for enhanced species resolution. The study identified six Bradyrhizobium species: Bradyrhizobium japonicum USDA 110, Bradyrhizobium japonicum USDA 6, Bradyrhizobium elkanii USDA 76, Bradyrhizobium neotropicale, Bradyrhizobium lablabi, and Bradyrhizobium icense. Bradyrhizobium japonicum USDA 110 predominated in the soils, displaying symbiotic preference for the Huasteca 400 variety. However, phylogenetic analysis didn't reveal a clear association between strains, soil, and soybean variety. This research sheds light on the diversity of rhizobia in Mexican soybean cultivation, contributing to the understanding of symbiotic relationships in soybean production systems.

Mapping and identification of QTLs for seed fatty acids in soybean(Glycine max L.)

Soybean is one of the most important sources of vegetable oil.The oil content and fatty acid ratio have attracted significant attention due to their impacts on the shelf-life of soybean oil products and consumer health.In this study,a high-density genetic map derived from Guizao 1 and Brazil 13 was used to analyze the quantitative trait loci of palmitic acid(PA),stearic acid(SA),oleic acid(OA),linoleic acid(LA),linolenic acid(LNA),and oil content(OC).A total of 54 stable QTLs were detected in the genetic map linkage analysis,which shared six bin intervals.Among them,the bin interval on chromosome 13(bin106-bin118 and bin123-bin125)was found to include stable QTLs in multiple environments that were linked to OA,LA,and LNA.Eight differentially expressed genes(DEGs)within these QTL intervals were determined as candidate genes according to the combination of parental resequencing,bioinformatics and RNA sequencing data.All these results are conducive to breeding soybean with the ideal fatty acid ratio for food,and provide the genetic basis for mining genes related to the fatty acid and oil content traits in soybean.