Soybean Stem Research Articles

Effectiveness of Elephant Grass (Pennisetum purpureum) Green Fertilizer on the Growth of Soybean Plants (Glycine max L. Merrill)

Soybeans (Glycine max L. Merrill) After rice and corn, it is the third most important food commodity and occupies a strategic position in the country's food policy, It plays a very important role in the nutrition of the Indonesian population. The aim of this study was to investigate the effects of soybean plant (Glycine Max). The aim of this study is to investigate the effects of green manure Pennisetum purpureum on plant growth (Merrill). The study was conducted in Batu Melengangan Village, Langkat Regency, using an experimental method involving 2 treatments, namely P0 (without green fertilizers) and P1 (200 grams of green elephant grass fertilizer), and a completely randomized, non-evidence-based design (CRD). In analyzing the data from this study, the SPSS program used parametric tests, i.e. Anova and Duncan tests, and nonparametric tests, i.e. KRUSKAL-Wallis and Mann-Whitney tests. The results of the study show that there was effectiveness of elephant grass green fertilizer (Pennisetum purpureum) on the growth of soybean stem height with an average of 36.25 cm, number of soybean leaves with an average of 46,775 pieces, the age at which soybean flowers emerged with an average of 36.6 days, and the age at which soybeans emerge is an average of 43.2 days. The most effective green manure treatment for the growth of soybean plants (Glycine max L. Merrill) was in treatment P1 (200 gr grass green manure).

QTL Mapping and Candidate Gene Mining for Stem Diameter Using Genetic Basis of Cultivated Soybean and Wild Soybean

Soybean (Glycine max) is a vital food crop, serving as a major source of high-quality protein for human and animal consumption. Stem diameter is one of the primary determinants of the stem lodging resistance of a given plant, but there has been relatively little research to date focused on genes associated with this trait. To address this gap in the literature, 207 chromosome segment substitution lines (CSSLs) were generated in the present study through the crossing and backcrossing of the improved Suinong14 and the wild ZYD00006 soybean varieties. These CSSLs were then used for the mapping of quantitative trait loci (QTLs) associated with stem diameter in two-year field planting materials, leading to the identification of nine QTLs. Whole genome resequencing, RNA-seq, and qPCR were then used to evaluate candidate genes associated with stem diameter within these QTL intervals, ultimately leading to the selection of Glyma.04G004100 as a stem diameter-related gene. Subsequent qPCR analyses revealed that Glyma.04g004100 was upregulated in soybean plants with larger stem diameters, and haplotype analyses yielded results consistent with these stem diameter data in the population used to conduct this study. In summary, a series of QTLs associated with stem diameter were identified in the present study, resulting in the establishment of Glyma.04g004100 as a stem diameter-related gene. Together, these results offer a theoretical foundation for the future molecular-assisted breeding of lodging-resistant soybean varieties, and future functional research focused on Glyma.04g004100 may elucidate the molecular mechanisms and key signaling networks involved in soybean stem development.

Pengaruh Kombinasi Populasi Tumpangsari Kedelai-Singkong pada Pertumbuhan dan Hasil Benih Tanaman Kedelai dan Hasil Umbi Singkong

Intercropping soybeans with cassava can become one solution to increase the production of soybean in Indonesia. This research aimed to determine the most optimal population combination of soybean-cassava intercropping for the growth and yield of soybean seeds, cassava tuber yield, and land use efficiency (LUE).. The research was carried out on the farm land of the Main Seed Center in Sekincau District, West Lampung Regency, Lampung Province, Indonesia at -5°02’27” South and 104°18’16” East at elevation of 1173.1 meter from sea level and at the Seed and Plant Breeding Laboratory Faculty of Agriculture University of Lampung during June 2022 - February 2023. The four treatments of population combination of soybean-cassava intercropping were applied in a completely randomized block design (CRBD) and replicated five times in five blocks. The four population combination treatments of soybean-cassava intercropping were a) 100% soybean and 0% cassava (monoculture) (p₁), b) 67% soybean and 97% cassava (p₂), c) 67% soybean and 89% cassava (p₃), and d) 50% soybeans and 97% cassava (p₄). The growth and the seed yield per soybean stem of monoculture did not differ to those of the soybean-cassava intercropping, but the soybean seed yield per plot area of the intercropping was lower than those of monoculture. Its mainly due to the soybean population of the intercropping was lower compared to monoculture. All population combinations in soybean-cassava intercropping were effective in supporting the growth and yield of soybean seeds, but the population combination of 50% soybean and 97% cassava (p₄) was also effective in supporting cassava tuber yield, and had the highest land use efficiency among other population combinations. Key words: flowering age, plant height, seed weight, tuber weight of cassava

Effects of narrow-wide row planting patterns on canopy photosynthetic characteristics, bending resistance and yield of soybean in maize‒soybean intercropping systems

With the improvements in mechanization levels, it is difficult for the traditional intercropping planting patterns to meet the needs of mechanization. In the traditional maize‒soybean intercropping, maize has a shading effect on soybean, which leads to a decrease in soybean photosynthetic capacity and stem bend resistance, resulting in severe lodging, which greatly affects soybean yield. In this study, we investigated the effects of three intercropping ratios (four rows of maize and four rows of soybean; four rows of maize and six rows of soybean; six rows of maize and six rows of soybean) and two planting patterns (narrow-wide row planting pattern of 80–50 cm and uniform-ridges planting pattern of 65 cm) on soybean canopy photosynthesis, stem bending resistance, cellulose, hemicellulose, lignin and related enzyme activities. Compared with the uniform-ridge planting pattern, the narrow-wide row planting pattern significantly increased the LAI, PAR, light transmittance and compound yield by 6.06%, 2.49%, 5.68% and 5.95%, respectively. The stem bending resistance and cellulose, hemicellulose, lignin and PAL, TAL and CAD activities were also significantly increased. Compared with those under the uniform-ridge planting pattern, these values increased by 7.74%, 3.04%, 8.42%, 9.76%, 7.39%, 10.54% and 8.73% respectively. Under the three intercropping ratios, the stem bending resistance, cellulose, hemicellulose, lignin content and PAL, TAL, and CAD activities in the M4S6 treatment were significantly greater than those in the M4S4 and M6S6 treatments. Compared with the M4S4 treatment, these variables increased by 12.05%, 11.09%, 21.56%, 11.91%, 18.46%, 16.1%, and 16.84%, respectively, and compared with the M6S6 treatment, they increased by 2.06%, 2.53%, 2.78%, 2.98%, 8.81%, 4.59%, and 4.36%, respectively. The D-M4S6 treatment significantly improved the lodging resistance of soybean and weakened the negative impact of intercropping on soybean yield. Therefore, based on the planting pattern of narrow-wide row maize‒soybean intercropping planting pattern, four rows of maize and six rows of soybean were more effective at improving the lodging resistance of soybean in the semiarid region of western China.

Distribution of Charcoal Rot of Soybean, its Influencing Factors and Pathogenic Variabilities in Different Regions of Madhya Pradesh

Background: Macrophomina phaseolina (Tassi) Goid is a necrotrophic soil-inhabiting fungus that causes disease in several economic plants worldwide and has now become a serious threat to soybean cultivation in central India. Methods: The random surveys were done during 2018 and 2019 to determine the present status of charcoal rot (M. phaseolina) in key soybean growing districts of Madhya Pradesh. Sixteen isolates of pathogen were characterized based on morpho-cultural and pathogenic variability by using cut stem inoculation techniques at J.N.K.V.V., Jabalpur. Result: Charcoal rot was prevalent in all surveyed sixteen districts of Madhya Pradesh. Out of six, Kymore plateau and Satpura hills (44.5%), Satpura plateau (42.5%), Central Narmada Valley (42.0%) and Vindhyan plateau agroclimatic zones (35.0%) were identified as favouable zones for charcoal rot. Malwa plateau (16.25%) and Northern hill region (24.5%) had low incidences of charcoal rot. Among varieties, JS 95-60, JS 93-05 and JS 20-29 were highly affected, whereas, JS 20-34, JS 20-98 and JS 20-69 were least affected. Incidence of charcoal rot was comparatively higher in the fields that had Maize-Chickpea (26.32%), Maize-Wheat, Soybean- Pea and Soybean - Chickpea cropping patterns in the previous year and lowest in Rice-Chickpea (12.00%) and Rice - Wheat (12.45%) cropping patterns. The incidence of charcoal rot was partially higher in the fields with light soil (21.3%) than in heavy soil (19.0%). Isolates investigation revealed that isolates from Jabalpur, Hoshangabad, Chhindwara and Sagar were fast-growing variables and highly aggressive in developing necrotic lesions on the cut stem of soybean. This investigation could be instrumental in forewarning sensitive areas of charcoal rot, varietal options and crop rotation to be followed to minimize the incidence of charcoal rot. Moreover, identified variable aggressive isolates could be utilized in genotype resistance screening programs.

Resistance mechanism of Phomopsis longicolla to fludioxonil is associated with modifications in PlOS1, PlOS4 and PlOS5

Phomopsis longicolla, a causal agent of soybean root rot, stem blight, seed decay, pod and stem canker, which seriously affects the yield and quality of soybean production worldwide. The phenylpyrrole fungicide fludioxonil exhibits a broad spectrum and high activity against phytopathogenic fungi. In this study, the baseline sensitivity of 100 P. longicolla isolates collected from the main soybean production areas of China to fludioxonil were determined. The result showed that the EC50 values of all the P. longicolla isolates ranged from 0.013 to 0.035 μg/ml. Furthermore, 12 fludioxonil-resistance (FluR) mutants of P. longicolla were generated from 6 fludioxonil-sensitive (FluS) isolates. and the resistance factors (RF) of 12 FluR mutants were >3500. Sequence alignment showed that multiple mutation types were found in PlOS1, PlOS4 or/and PlOS5 of FluR mutants. All the FluR mutants exhibited fitness penalty in mycelial growth, conidiation, virulence and osmo-adaptation. Under fludioxonil or NaCl treatment condition, the glycerol accumulation was significantly increased in FluS isolates, but was slightly increased in FluR mutants, and the phosphorylation level of most FluR mutants was significantly decreased when compared to the FluS isolates. Additionally, positive cross-resistance was observed between fludioxonil and procymidone but not fludioxonil and pydiflumetofen, pyraclostrobin or fluazinam. This is first reported that the baseline sensitivity of P. longicolla to fludioxonil, as well as the biological and molecular characterizations of P. longicolla FluR mutants to fludioxonil. These results can provide scientific directions for controlling soybean diseases caused by P. longicolla using fludioxonil.

Genome-Wide Association Study on Candidate Genes Associated with Soybean Stem Pubescence and Hilum Colors

The colorations of stem pubescence and hilum are crucial criteria for discerning diverse soybean germplasms, governed by multiple genes that substantially influence the seed’s outward appearance quality and the resistance to abiotic stresses. This comprehensive study delved into the stem pubescence and hilum color traits across a natural population of 264 accessions during 2021 and 2022. The phenotypes of these two traits within our population were analyzed for the investigation of population genetics and evaluation of germplasm resources in the future. Numerous noteworthy SNPs associated with both traits were detected through a genome-wide association study (GWAS), with the most significant signals for 2021 and 2022 localized on chromosome 6. Seven candidate genes regulating stem pubescence color and four genes influencing hilum color were identified by analyzing the expression patterns, cold stress responses, and regulatory pathways of genes within the LD decay distance of SNPs. This study not only underscores the applicability of GWAS in unraveling the genetic basis of quality traits, but also contributes novel genetic reservoirs and research paradigms to the explorations of the soybean plant and seed color. These results provide foundational insights into the breeding improvement of seeds’ outward appearance quality and a comprehensive evaluation of soybean germplasm.

First Report of Foliar Nematode (Aphelenchoides pseudobesseyi) on Soybean in Colombia

Soybean (Glycine max L.) is produced in over 70,000 ha in the Altillanura Region, eastern Colombia (Agronet 2023). From 2018 to 2020, foliar symptoms like green stem and foliar retention of soybean, which in Brazil can cause up to 100% soybean yield losses (Meyer et al. 2017), were observed in soybean fields in Colombia. During 2020, samples from symptomatic plants in reproductive stages (R1-R8) were collected from different commercial soybean fields in the Altillanura Region. Over 200 samples were processed, using an incubation method described in Coyne et al. (2014). Nematodes were recovered from photosynthetic leaf tissues and enlarged nodes/buds with population densities ranging from 13 to 132 and 36 to 936 nematodes/10g, respectively. Adult females were morphologically and molecularly characterized as Aphelenchoides pseudobesseyi (Oliveira et al. 2019; Subbotin et al. 2020). Female body length (n = 20) ranged from 653.3 to 806.3 μm (mean = 723 μm ± 52.7), stylet length from 11.0 to 12.3 μm (11.8 μm ± 0.3), body diameter from 14.8 to 17.9 μm (16.3 μm ± 1.1), post-uterine sac length from 38.7 to 51.9 μm (44.6 μm ± 5.1), vulva to anus from 145.5 to 223.2 μm (172.2 μm ± 22.4), and 26% of the vulva-anus distance. Genomic DNA was extracted (QIAGEN DNeasy® Blood & Tissue kit) from a pool of nematodes. The D2A/D3B (Tenente et al. 2004) primers were used to amplify and sequence the D2/D3 expansion region of the 28S rRNA gene. PCR product (~759 bp) was purified, sequenced, deposited in GenBank (OQ930285), and compared to previously deposited sequences (e.g., KX356756, KY510840, KY510839, KY510841, KT692694, KY510842, MH187565) by means of the BLAST algorithm. Similarly, 988F and 18SR-Burs (De Jesus et al. 2016) primers were used to amplify and sequence the near full-length 18S RNA gene (SSU). PCR product was purified, sequenced, deposited in GenBank (OQ954344), and compared to previously deposited sequences (e.g., KT454962, KT943534, KT943535, KY510835, KY510836, KY510837, KY510838, MH187565). Phylogenetic Bayesian analysis (Ronquist et al. 2012) of the of the D2/D3 and 18S regions placed this nematode from Colombia in the A. pseudobesseyi clade (PP = 100). To fulfill a modified Koch’s postulates, the A. pseudobesseyi population described above was used in a greenhouse assay. In total, 120 soybean plants (cv. Flor Blanca) were infected with 200 A. pseudobesseyi (females + males)/plant. Briefly, at cotyledon stage (VC), 50 µl aliquot containing 50 A. pseudobesseyi was delivered onto each cotyledon and unifoliolate leaves (200 nematodes/plant). Sterile water was delivered to 80 plants which served as control. Plants were kept in the greenhouse at approximately 25°C and covered with clear plastic bag for 72 h to maintain over 90% relative humidity. After 15, 30, 45, and 60 days, soybean plants (n = 20) were processed, A. pseudobesseyi quantified, and the average reproduction factor (final population/initial population) was 0.1, 2.9, 14.0, and 1.8, respectively. Infected plants showed symptoms of blistering leaves with malformation (midrib vein twist), and A. pseudobesseyi was not observed in control plants. To our knowledge, this is the first report of A. pseudobesseyi parasitizing soybean buds and leaves in Colombia. Soybean is an important commodity for the Altillanura Region, and it is important to monitor the risk posed by this nematode. Furthermore, a better understanding of the nematode-host interaction and epidemiology in Colombia soybean producing regions is needed.

First record of Soybean Stem Fly Melanagromyza sojae (Zehntner, 1901) (Diptera, Agromyzidae) in Uruguay confirmed by DNA barcoding

Colloquially known as Soybean Stem Fly, Melanagromyza sojae (Zehntner, 1901) (Diptera, Agromyzidae) is an oligophagous pest of plants in the family Fabaceae, including Uruguay’s biggest commodity crop, Soybean (Glycine max (L.) Merr.). To our knowledge, this is the first scientific record of M. sojae in Uruguay, and we confirm its identity through using DNA barcoding. Characteristic damage to host plants and immature stages of M. sojae were confirmed in Dolores and Colonia, Uruguay.

QTL mapping and genomic selection of stem and branch diameter in soybean (Glycine max L.).

Soybean stem diameter (SD) and branch diameter (BD) are closely related traits, and genetic clarification of SD and BD is crucial for soybean breeding. SD and BD were genetically analyzed by a population of 363 RIL derived from the cross between Zhongdou41 (ZD41) and ZYD02878 using restricted two-stage multi-locus genome-wide association, inclusive composite interval mapping, and three-variance component multi-locus random SNP effect mixed linear modeling. Then candidate genes of major QTLs were selected and genetic selection model of SD and BD were constructed respectively. The results showed that SD and BD were significantly correlated (r = 0.74, P < 0.001). A total of 93 and 84 unique quantitative trait loci (QTL) were detected for SD and BD, respectively by three different methods. There were two and ten major QTLs for SD and BD, respectively, with phenotypic variance explained (PVE) by more than 10%. Within these loci, seven genes involved in the regulation of phytohormones (IAA and GA) and cell proliferation and showing extensive expression of shoot apical meristematic genes were selected as candidate genes. Genomic selection (GS) analysis showed that the trait-associated markers identified in this study reached 0.47-0.73 in terms of prediction accuracy, which was enhanced by 6.56-23.69% compared with genome-wide markers. These results clarify the genetic basis of SD and BD, which laid solid foundation in regulation gene cloning, and GS models constructed could be potentially applied in future breeding programs.

Rapid and sensitive detection of two fungal pathogens in soybeans using the recombinase polymerase amplification/CRISPR-Cas12a method for potential on-site disease diagnosis.

Diaporthe aspalathi and Diaporthe caulivora are two of the fungal pathogens causing soybean stem canker (SSC) in soybean, which is one of the most widespread diseases in soybean growing regions and can cause 100% loss of yield. Current methods for the detection of fungal pathogens, including morphological identification and molecular detection, are mostly limited by the need for professional laboratories and staff. To develop a detection method for potential on-site diagnosis for two of the fungal pathogens causing SSC, we designed a rapid assay combining recombinase polymerase amplification (RPA) and CRISPR-Cas12a-based diagnostics to specifically detect D. aspalathi and D. caulivora. The translation elongation factor 1-alpha gene was employed as the target gene to evaluate the specificity and sensitivity of this assay. The RPA/CRISPR-Cas12a system has excellent specificity to distinguish D. aspalathi and D. caulivora from closely related species. The sensitivities of RPA/CRISPR-Cas12a-based fluorescence detection and lateral flow assay for D. aspalathi and D. caulivora are 14.5 copies and 24.6 copies, respectively. This assay can detect hyphae in inoculated soybean stems at 12 days after inoculation and has a recovery as high as 86% for hyphae-spiked soybean seed powder. The total time from DNA extraction to detection was not more than 60 min. The method developed for rapid detection of plant pathogens includes DNA extraction with magnetic beads or rapid DNA extraction, isothermal nucleic acid amplification at 39 °C, CRISPR-Cas12a cleavage reaction at 37 °C, and lateral flow assay or endpoint fluorescence visualization at room temperature. The RPA and CRISPR-Cas12a reagents can be preloaded in the microcentrifuge tube to simplify the procedures in the field. Both RPA and CRISPR-Cas12a reaction can be realized on a portable incubator, and the results are visualized using lateral flow strips or portable flashlight. This method requires minimal equipment and operator training, and has promising applications for rapid on-site disease screening, port inspection, or controlling fungal pathogen transmission in crop. © 2023 Society of Chemical Industry.

Identification and mapping of a recessive allele, dt3, specifying semideterminate stem growth habit in soybean

Key messageA locus, dt3, modulating semideterminancy in soybean, was discovered by a combination of genome-wide association studies and linkage mapping with multiple distinct biparental populations.Stem growth habit is a key architectural trait in many plants that contributes to plant productivity and environmental adaptation. In soybean, stem growth habit is classified as indeterminate, semideterminate, or determinate, of which semideterminacy is often considered as a counterpart of the “Green Revolution” trait in cereals that significantly increased grain yields. It has been demonstrated that semideterminacy in soybean is modulated by epistatic interaction between two loci, Dt1 on chromosome 19 and Dt2 on chromosome 18, with the latter as a negative regulator of the former. Here, we report the discovery of a third locus, Dt3, modulating soybean stem growth habit, which was delineated to a ~ 196-kb region on chromosome 10 by a combination of allelic and haplotypic analysis of the Dt1 and Dt2 loci in the USDA soybean Germplasm Collection, genome-wide association studies with three subsets of the collection, and linkage mapping with four biparental populations derived from crosses between one of two elite indeterminate cultivars and each of four semideterminate varieties possessing neither Dt2 nor dt1. These four semideterminate varieties are recessive mutants (i.e., dt3/dt3) in the Dt1/Dt1;dt2/dt2 background. As the semideterminacy modulated by the Dt2 allele has unfavorable pleotropic effects such as sensitivity to drought stress, dt3 may be an ideal alternative for use to develop semideterminate cultivars that are more resilient to such an environmental stress. This study enhances our understanding of the genetic factors underlying semideterminacy and enables more accurate marker-assisted selection for stem growth habit in soybean breeding.

Damage Assessment of Melanagromyza sojae (Diptera: Agromyzidae) on Soybean in Brazil

Soybean stem fly, Melanagromyza sojae Zehntner (Diptera: Agromyzidae), is an important soybean (Glycine max) pest in Eastern Asia that has recently colonized South America. The region colonized by M. sojae includes Brazil and several other major soybean growing countries. Management strategies for this pest remain largely undeveloped due to lack of information regarding its potential to injury soybeans. The objective of this study was to quantify soybean yield reduction caused by M. sojae injury. One experiment was carried out during two summer crop seasons (2020 and 2021) at Santa Maria, RS state, Brazil. Soybean was planted during late-season to ensure that high pressure of M. sojae adults were present in the fields. The number of seeds, 1,000-seed weight, seed yield and number of pods were quantified for the lower, middle and upper canopy, and plant height was compared to the amount of stem injured to determine percentage of injured stem. Each 1% of injured stem in the lower, middle and upper canopy segments significantly reduced the number of seeds per plant, 1,000-seed weight, and yield. Across all canopy segments, yield reduction reached 0.9 g per plant for every 1% of injured stem. Treatments where insecticide applications started during the vegetative phase presented the lowest damage by M. sojae. These data suggest that M. sojae is an economically important herbivore of soybeans under Brazilian growing conditions and highlight the need to develop efficient and sustainable management strategies for this pest.

Current understanding of the Diaporthe/Phomopsis complex causing soybean stem canker: A focus on molecular aspects of the interaction

AbstractSoybean stem canker (SSC) is an important disease caused by different Diaporthe spp., including D. aspalathi, D. caulivora and D. longicolla, that leads to soybean (Glycine max) yield losses around the world. Most studies have been focused on the morphological characterization and molecular identification of Diaporthe spp. present in SSC lesions. Several soybean resistance loci to Diaporthe spp. causing SSC have been identified, although the molecular identities of the resistance genes are at present unknown. In this review, we summarize the current knowledge on SSC disease, the molecular characterization of Diaporthe spp. and their evolutionary relationships. We highlight how recent genomic and transcriptomic information is allowing significant progress in our understanding of the molecular components and mechanisms underlying Diaporthe infection strategies as well as soybean disease resistance. The information generated, combined with available resources enabling functional genomics, will contribute to the development of breeding strategies for disease resistance, leading to a more sustainable agriculture.

Comparative analysis of soybean transcriptional profiles reveals defense mechanisms involved in resistance against Diaporthe caulivora

Soybean stem canker (SSC) caused by the fungal pathogen Diaporthe caulivora is an important disease affecting soybean production worldwide. However, limited information related to the molecular mechanisms underlying soybean resistance to Diaporthe species is available. In the present work, we analyzed the defense responses to D. caulivora in the soybean genotypes Williams and Génesis 5601. The results showed that compared to Williams, Génesis 5601 is more resistant to fungal infection evidenced by significantly smaller lesion length, reduced disease severity and pathogen biomass. Transcriptional profiling was performed in untreated plants and in D. caulivora-inoculated and control-treated tissues at 8 and 48 h post inoculation (hpi). In total, 2.322 and 1.855 genes were differentially expressed in Génesis 5601 and Williams, respectively. Interestingly, Génesis 5601 exhibited a significantly higher number of upregulated genes compared to Williams at 8 hpi, 1.028 versus 434 genes. Resistance to D. caulivora was associated with defense activation through transcriptional reprogramming mediating perception of the pathogen by receptors, biosynthesis of phenylpropanoids, hormone signaling, small heat shock proteins and pathogenesis related (PR) genes. These findings provide novel insights into soybean defense mechanisms leading to host resistance against D. caulivora, and generate a foundation for the development of resistant SSC varieties within soybean breeding programs.

A Phytophthora receptor-like kinase regulates oospore development and can activate pattern-triggered plant immunity

Plant cell-surface leucine-rich repeat receptor-like kinases (LRR-RLKs) and receptor-like proteins (LRR-RLPs) form dynamic complexes to receive a variety of extracellular signals. LRR-RLKs are also widespread in oomycete pathogens, whereas it remains enigmatic whether plant and oomycete LRR-RLKs could mediate cell-to-cell communications between pathogen and host. Here, we report that an LRR-RLK from the soybean root and stem rot pathogen Phytophthora sojae, PsRLK6, can activate typical pattern-triggered immunity in host soybean and nonhost tomato and Nicotiana benthamiana plants. PsRLK6 homologs are conserved in oomycetes and also exhibit immunity-inducing activity. A small region (LRR5-6) in the extracellular domain of PsRLK6 is sufficient to activate BAK1- and SOBIR1-dependent immune responses, suggesting that PsRLK6 is likely recognized by a plant LRR-RLP. Moreover, PsRLK6 is shown to be up-regulated during oospore maturation and essential for the oospore development of P. sojae. Our data provide a novel type of microbe-associated molecular pattern that functions in the sexual reproduction of oomycete, and a scenario in which a pathogen LRR-RLK could be sensed by a plant LRR-RLP to mount plant immunity.

A Shift in Pathotype Diversity and Complexity of Phytophthora sojae in Brazil.

Soybean root and stem rot caused by the oomycete Phytophthora sojae is a destructive disease worldwide that can affect plants at any growth stage. The use of resistant cultivars is the most effective method of controlling the disease. Therefore, monitoring changes in the population of P. sojae regarding the dynamics of avirulence genes capable of overcoming resistance genes (Rps) is important to reduce yield losses and to enhance the effectiveness of the Rps genes. Forty isolates of P. sojae sampled from a region of high incidence of soybean root and stem rot in Brazil were characterized using 14 soybean differentials, and 28 pathotypes were identified. Compared with a study conducted a decade ago, there was a major shift in pathotype diversity and complexity toward both higher numbers of different pathotypes and of avirulence genes in a given individual in the current population of P. sojae. Breeding programs aiming at developing soybean cultivars with resistance to root and stem rot should consider the high variability in the population of P. sojae and seek for strategic deployment of genes and germplasm.

Susceptibility of the Most Popular Soybean Cultivars in South-East Europe to Macrophomina phaseolina (Tassi) Goid.

Oxidative stress in soybean seedlings and the length of the soybean stem lesions infected with the fungus Macrophomina phaseolina (Tassi) Goid were evaluated to determine the most tolerant soybean cultivar to this pathogen. The level of superoxide anion radical (O2•-) production, the activity of the antioxidant enzyme superoxide-dismutase (SOD), and the intensity of lipid peroxidation (LP) were measured in four soybean cultivars: Favorit, Atlas, Victoria, and Rubin. Results showed that O2•- radical production and SOD activity were the most elevated in the cv. Favorit inoculated with M. phaseolina, while the level of lipid peroxidation intensity was the lowest compared to the control. This indicates that the soybean cv. Favorit has managed to prevent infection with M. phaseolina. Furthermore, higher O2•- radical production and lower SOD enzyme activity were measured in cv. Victoria, with enhanced lipid peroxidation. This means that the cv. Victoria was infected with M. phaseolina, and was the most sensitive. None of the tested oxidative stress parameters showed a significant difference in the cvs. Atlas and Rubin compared to the control. Furthermore, the highest lesion length was measured in the cv. Victoria, followed by cv. Favorit, while the lowest lesion length was measured in the cv. Atlas followed by the cv. Rubin; and thus, the cv. Atlas followed by the cv. Rubin, were the most tolerant soybean cultivars to this pathogen.

Phyto-oxylipin mediated plant immune response to colonization and infection in the soybean-Phytophthora sojae pathosystem.

Food security is a major challenge to sustainably supply food to meet the demands of the ever-growing global population. Crop loss due to pathogens is a major concern to overcoming this global food security challenge. Soybean root and stem rot caused by Phytophthora sojae results in approximately 20B $US crop loss annually. Phyto-oxylipins are metabolites biosynthesized in the plants by oxidative transformation of polyunsaturated fatty acids through an array of diverging metabolic pathways and play an important role in plant development and defense against pathogen colonization and infection. Lipid mediated plant immunity is a very attractive target for developing long term resistance in many plants' disease pathosystem. However, little is known about the phyto-oxylipin's role in the successful strategies used by tolerant soybean cultivar to mitigate Phytophthora sojae infection. We used scanning electron microscopy to observe the alterations in root morphology and a targeted lipidomics approach using high resolution accurate mass tandem mass spectrometry to assess phyto-oxylipin anabolism at 48h, 72h and 96h post infection. We observed the presence of biogenic crystals and reinforced epidermal walls in the tolerant cultivar suggesting a mechanism for disease tolerance when compared with susceptible cultivar. Similarly, the unequivocally unique biomarkers implicated in oxylipin mediated plant immunity [10(E),12(Z)-13S-hydroxy-9(Z),11(E),15(Z)-octadecatrienoic acid, (Z)-12,13-dihydroxyoctadec-9-enoic acid, (9Z,11E)-13-Oxo-9,11-octadecadienoic acid, 15(Z)-9-oxo-octadecatrienoic acid, 10(E),12(E)-9-hydroperoxyoctadeca-10,12-dienoic acid, 12-oxophytodienoic acid and (12Z,15Z)-9, 10-dihydroxyoctadeca-12,15-dienoic acid] generated from intact oxidized lipid precursors were upregulated in tolerant soybean cultivar while downregulated in infected susceptible cultivar relative to non-inoculated controls at 48h, 72h and 96h post infection by Phytophthora sojae, suggesting that these molecules may be a critical component of the defense strategies used in tolerant cultivar against Phytophthora sojae infection. Interestingly, microbial originated oxylipins, 12S-hydroperoxy-5(Z),8(Z),10(E),14(Z)-eicosatetraenoic acid and (4Z,7Z,10Z,13Z)-15-[3-[(Z)-pent-2-enyl]oxiran-2-yl]pentadeca-4,7,10,13-tetraenoic acid were upregulated only in infected susceptible cultivar but downregulated in infected tolerant cultivar. These microbial originated oxylipins are capable of modulating plant immune response to enhance virulence. This study demonstrated novel evidence for phyto-oxylipin metabolism in soybean cultivars during pathogen colonization and infection using the Phytophthora sojae-soybean pathosystem. This evidence may have potential applications in further elucidation and resolution of the role of phyto-oxylipin anabolism in soybean tolerance to Phytophthora sojae colonization and infection.

Optimum nitrogen improved stem breaking resistance of intercropped soybean by modifying the stem anatomical structure and lignin metabolism

Excessive use of nitrogen fertilizers enhanced the stem lodging, leading to serious threats to environmental sustainability. As the maize-soybean intercropping system is eco-friendly, however, soybean micro-climate hinders soybean growth and caused lodging. Since the relationship between nitrogen and lodging resistance under the intercropping system is not widely studied. Therefore, a pot experiment was conducted with the application of different nitrogen concentrations referring to low nitrogen (LN) = 0 mg/kg, optimum nitrogen (OpN) = 100 mg/kg, and high nitrogen (HN) = 300 mg/kg. To evaluate the optimum nitrogen fertilization under the maize-soybean intercropping system, two soybean cultivars were selected Tianlong 1 (TL-1), (lodging resistant) and Chuandou 16 (CD-16), (lodging susceptible). The results revealed that under the intercropping system, the OpN concentration significantly improved the lodging resistance of soybean cultivars by reducing the plant height of TL-1 and CD-16 by 4 and 28% as compared to LN, respectively. Following OpN, the lodging resistance index for CD-16 was also increased by 67% and 59% under the respective cropping systems. In addition, we found that OpN concentration prompted the lignin biosynthesis by stimulating the enzymatic activities of lignin biosynthetic enzymes (PAL, 4CL, CAD, and POD), which was reflected at the transcriptional levels (GmPAL, GmPOD, GmCAD, Gm4CL), too. Henceforth, we proposed that optimum nitrogen fertilization boosts soybean stem lodging resistance by modulating the lignin metabolism in the maize-soybean intercropping system.