Pod Abortion Research Articles

Assessing Seed Treatments to Control Sudden Death Syndrome Caused by Fusarium virguliforme and Seedling and Root Disease Caused by Rhizoctonia sp. on Mungbean (Vigna radiata)

There is growing interest in producing mungbean ( Vigna radiata L. Wilczek) in the United States, which is driven by increased consumer demand. Strategies are needed for United States farmers to take advantage of this high-value crop and its environmental sustainability. Recommendations for the management of mungbean seedling and root diseases are lacking. Preliminary research in central Iowa mungbean fields from 2019 to 2023 has shown that mungbean is particularly vulnerable to Fusarium virguliforme, the cause of soybean sudden death syndrome (SDS), and Rhizoctonia sp., the cause of damping-off, root decay, premature defoliation, and pod abortion. The purpose of this study was to screen a variety of fungicides as a seed treatment or a soil band application to control root rot in mungbean. We performed three field studies over 2 years using mungbean cultivars Berken and OK2000. Seed treatments Evergol Energy + fluopyram and Evergol Energy + pydiflumetofen showed the highest performance ( P < 0.05), with approximately 30% more healthy roots than nontreated controls. Other treatments exhibited about 20% more healthy roots than the nontreated control. Biotam in-furrow application showed the highest plant population for ‘OK2000’, but we observed no treatment differences in plant stand for ‘Berken’.

β-caryophyllene as an attractant for the cacao mirid bug, Helopeltis bakeri Poppius (Hemiptera: Miridae), and chemodiversity of its host plant volatiles

The cacao mirid bug, Helopeltis bakeri, is a major insect pest of cacao in the Philippines. It feeds on pods causing puncture wounds that become necrotic lesions and may lead eventually to pod abortion. There is currently no semiochemical-based system developed for the monitoring and control of H. bakeri. Here, we report a kairomone identified from host plants of H. bakeri as a potential attractant. Volatile components were extracted using solid-phase microextraction (100-µm polydimethylsiloxane) and analyzed by gas chromatography - mass spectrometry. Chemodiversity analysis considering compound richness, evenness, and disparity showed similar phytochemical diversity among the six host plants, suggesting that chemodiversity is a factor in the host selection behavior of H. bakeri. Comparison of volatiles revealed that β-caryophyllene was present in all host plants. Using a wind tunnel, an impregnated lure containing 90 µg β-caryophyllene showed the highest attraction to adult H. bakeri. The results show the potential of β-caryophyllene as attractant that can be used in the development of kairomone-based trapping systems for H. bakeri as part of a holistic integrated pest management system for cacao.

Epidemiology of soybean bud proliferation and seed pod abortion disease in Iran

Epidemiology of soybean bud proliferation and seed pod abortion disease in Iran

Effect of assimilate competition during early seed development on the pod and seed growth traits in soybean.

Although the seed remains small in size during the initial stage of seed development (the lag phase), several studies indicate that environment and assimilate supply level manipulations during the lag phase affect the final seed size. However, the manipulations were not only at the lag phase, making it difficult to understand the specific role of the lag phase in final seed size determination. It also remained unclear whether environmental cues are sensed by plants and regulate seed development or if it is simply the assimilate supply level, changed by the environment, that affects the subsequent seed development. We investigated soybean (Glycine max L. Merr.) seed phenotypes grown in a greenhouse using different source-sink manipulations (shading and removal of flowers and pods) during the lag phase. We show that assimilate supply is the key factor controlling flower and pod abortion and that the assimilate supply during the lag phase affects the subsequent potential seed growth rate during the seed filling phase. In response to low assimilate supply, plants adjust flower/pod abortion and lag phase duration to supply the minimum assimilate per pod/seed. Our results provide insight into the mechanisms whereby the lag phase is crucial for seed development and final seed size potential, essential parameters that determine yield.

Nitrogen and Nickel Foliar Application on Grain yield, Yield Components, and Quality of Soybean

ABSTRACT Foliar fertilization with nitrogen (N) and nickel (Ni) at the end of the vegetative stage can decrease the abortion of flowers and pods of the plants and increase the productivity and protein content of soybean. This study aimed to evaluate the effect of N and Ni foliar application on the yield components and oil and protein content in soybean. The experiment was performed in a completely randomized design with six treatments (control [only inoculation], urea, ammonium sulfate [AS], nickel chloride [NiCl2], NiCl2+ AS, and NiCl2+ urea) and five replicates. Foliar application with urea increased the soybean grain yield (GY) by 46%, whereas the NiCl2 foliar application or NiCl2+ urea and NiCl2+ AS applications decreased the GY, shoot dry weight (SDW), weight of pods per pot, root volume, and grain size. N (AS and urea) and NiCl2 foliar applications had no effect on the oil and protein content in the grains, and application of 60 g ha−1 of Ni (132.4 g of NiCl2) caused a toxic effect on the plants and negatively influenced the GY and quality of grains.

Can potassium fertilization alleviate the adverse effects of drought stress on soybean plants?

The adequate amounts of potassium (K) fertilizer application may play an essential role in the growth and tolerance of plants against the drought stress. In this study, the role of K in mitigating the adverse effects of drought stress on soybean plants [Glycine max (L.) Merrill.] was investigated in greenhouse conditions. Treatments were arranged in a randomized block design in a 2 × 3 factorial: two potassium fertilizer levels [40 mg K kg–1 (low) or 160 mg K kg–1 (high)] and three irrigation regimes [100% of pot capacity – PC (well watered control), 50% of PC (moderate stress) and 25% of PC (severe stress)] with four replicates. Leaf relative water content, cell membrane stability, plant growth, and morphophysiological indexes were recorded after 18 days of exposure to drought stress. The appropriate supply of potassium fertilizer improved leaf membrane stability and minimized the water loss from leaf tissue of soybean plants exposed to drought stress. The adverse effects of drought on leaf abscission and pod abortion rate could be mitigated by adequate K supply. The appropriate supply of potassium fertilizer alleviates the negative effects of drought stress and maintain shoot growth and the water status soybean plants, and therefore, the proper management of potassium fertilization may confer greater drought tolerance.

Cold Tolerance during the Reproductive Phase in Chickpea (Cicer arietinum L.) Is Associated with Superior Cold Acclimation Ability Involving Antioxidants and Cryoprotective Solutes in Anthers and Ovules.

Chickpea is sensitive to cold stress, especially at reproductive stage, resulting in flower and pod abortion that significantly reduces seed yield. In the present study, we evaluated (a) whether cold acclimation imparts reproductive cold tolerance in chickpea; (b) how genotypes with contrasting sensitivity respond to cold acclimation; and (c) the involvement of cryoprotective solutes and antioxidants in anthers and ovules in cold acclimation. Four chickpea genotypes with contrasting cold sensitivity (cold-tolerant: ICC 17258, ICC 16349; cold-sensitive: ICC 15567, GPF 2) were grown in an outdoor environment for 40 days in November (average maximum/minimum temperature 24.9/15.9 °C) before being subjected to cold stress (13/7 °C), with or without cold acclimation in a controlled environment of walk-in-growth chambers. The 42-d cold acclimation involved 7 d exposure at each temperature beginning with 23/15 °C, 21/13 °C, 20/12 °C, 20/10 °C, 18/8 °C, 15/8 °C (12 h/12 h day/night), prior to exposing the plants to cold stress (13/7 °C, 12 h/12 h day/night; 700 μmol m−2 s−1 light intensity; 65–70% relative humidity). Cold acclimation remarkably reduced low temperature-induced leaf damage (as membrane integrity, leaf water status, stomatal conductance, photosynthetic pigments, and chlorophyll fluorescence) under cold stress in all four genotypes. It only reduced anther and ovule damage in cold-tolerant genotypes due to improved antioxidative ability, measured as enzymatic (superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase) and non-enzymatic (ascorbate and reduced glutathione), solutes (particularly sucrose and γ-aminobutyric acid) leading to improving reproductive function and yield traits, whereas cold-sensitive genotypes were not responsive. The study concluded that cold tolerance in chickpea appears to be related to the better ability of anthers and ovules to acclimate, involving various antioxidants and cryoprotective solutes. This information will be useful in directing efforts toward increasing cold tolerance in chickpea.

Food Security Under The Era Of Climate Change Threat

Food Security Under The Era Of Climate Change Threat

Mycorrhizal Fungi and Potassium alleviating water stress imposed during different stages of growth in Phaseolus mungo

A pot experiment was conducted to evaluate the effect of Funneliformis mosseae, Acaulospora laevis and potassium (70ppm and 100ppm) on Phaseolus mungo imposed to water stress during three stages of growth. Water stress increased peroxidase activity and reduced nutrient uptake, nodulation and yield as compared to well watered plants. Our results revealed reproductive stage to be the worst stage to experience water stress as the flowers weathered away and reproductive growth shortened resulting in lesser no. of pods followed by pod formation stage during which pod abortion occurred and weight of the pods was negatively affected. Vegetative stage was found to be least affected by water stress. Treatment of plants with mycorrhizae and potassium improved antioxidant enzyme activities, nutrient uptake, nodulation and yield as compared to control. Since the plants stressed during the reproductive stage had minimum peroxidase activity, triple inoculation of plants with FAK2 resulted in maximum enhancement of peroxidase activity (0.882) among the different treatments. With the same treatment, shoot phosphorus (1.806) was found to be maximum during the pod formation stage. Root phosphorus (1.633), nodulation (23.6) and yield in terms of number (11.8) and weight of pods (6.84) were found to be maximum during vegetative stage with FAK2 followed by FAK1. Funneliformis mosseae proved to be an efficient alleviator of stress during all the stages as compared to Acaulospora laevis and either dose of potassium. Funneliformis mosseae along with K2 i.e. 100ppm was quite effective among double treatments.

Detection and molecular characterization of two genetically distinct phytoplasmas associated with mungbean seed pod abortion in Iran

New symptoms including aborted seed pods disease were observed on mungbean (Vigna radiata) plants in the most important growing areas in Iran that was similar to symptoms of phytoplasma disease previously reported from Australia. Thirty samples were collected from symptomatic and non-symptomatic plants, followed by PCR amplification, DNA sequencing, RFLP and phylogenetic analysis of 16S ribosomal RNA gene to detect and identify possible associated phytoplasmas. Results indicated that two different phytoplasmas, related to ‘Candidatus Phytoplasma trifolii’ and ‘Candidatus Phytoplasma aurantifolia’, were associated with different symptomatic plants samples from the same field, mixed infection was not observed in these samples. The sequence analysis results indicated that the nucleotide sequences from mungbean isolates 47 (MT674290), 7 (MT674291) and 32 (MT674292) had 98.8% sequence identity to ‘Candidatus Phytoplasma aurantifolia’ isolate TBBP-H1 (Acc. No: MN565885), while isolates 80 (MT674293) and 25 (MT674294) had 99.8% sequence identity similar to ‘Candidatus Phytoplasma trifolii’ (MF092789). In silico RFLP and phylogenetic analyse of mungbean seed pod abortion (MubSpa) phytoplasma indicated that the associated phytoplasmas belonged to phytoplasmas of subgroups 16SrVI-A and 16SrII-D. To the best of our knowledge, this is the first report of association ‘Ca. P. trifolii’ and ‘Ca. P. aurantifolia’ strains infecting mungbean plants in Iran.

Dynamics of abscission of reproductive structures in common bean access

Genotypes from the Andean and Mesoamerican gene pool can present contrasting behavior for reproductive structures fixation. The subject of this study was to determine the dynamics associated with the abscission of reproductive structures for common bean accesses from Andean and Mesoamerican gene pools in protected cultivation conditions. The experiment was carried out in a greenhouse, using seven common bean accesses from Embrapa Arroz e Feijão and the experimental design consisted of a randomized complete block design. The evaluations made were based on the number of days to begin flowering, flowering period, number of emitted flowers per plant, number of flower buds, flowers and pods aborted per plant, total number of pods per plant and number of seeds per plant.Certain characteristics were considered to be highly significant, such as the amount of days to begin flowering, the flowering period, percentage of aborted pods and number of harvested pods. The Mesoamerican accesses that presented greater abortion also produced more flowers, which suggests that abortion of reproductive structures can be a natural adjustment of the plant. Andean accessions with shorter reproductive period showed greater pod abortion. The dynamics of flower and pod abscission in the common bean proved to be widely variable depending on the different gene pools and genotypes evaluated and due to growth habit.

Detection and identification of a phytoplasma associated with rapeseedfasciation in Iran

During surveys in 2017 and 2018, a disease was observed in rapeseed fields in east of Iran. Affected plants exhibited extensive fasciation, formation of bunches of flowers, lack of leaves formation and seed pod abortion. The symptomatic rapeseed plants were analyzed for phytoplasma presence by nested PCR using phytoplasma universal primers and all tested symptomatic rapeseeds plants were positive for phytoplasma presence, while asymptomatic rapeseed plants were negative. Nested PCR positive samples were directly sequenced and in silico RFLP and phylogenetic analyses of PCR-amplified 16S rDNA sequences indicated the presence of a phytoplasma enclosed in the peanut witches’ broom broom group (16SrII). This is the first report of phytoplasma presence in rapeseed plants showing fasciation.

Co-Inoculation of Common Bean with Rhizobium and Azospirillum Enhance the Drought Tolerance

Plant growth-promoting rhizobacteria (PGPR) have been shown to reduce the negative effects of drought on numerous plant species, but these effects are unknown for common bean (Phaseolus vulgaris L.) crop. The study aimed to investigate the effects of inoculation with Rhizobium tropici, Azospirillum brasilense and the co-inoculation with both rhizobacteria on the nodulation, growth and tolerance of common bean plants to drought stress. Three water replenishment regimes [100% of pot capacity (non-stress control), 50% of pot capacity (moderate stress) and 25% of pot capacity (severe stress)] and four seed inoculation treatments: control (non-inoculated), inoculation with R. tropici, inoculation with A. brasilense; and co-inoculation with R. tropici and A. brasilense were studied in an experiment arranged in a 3 × 4 factorial scheme with four replicates. Relative water content (RWC), membrane stability index, nodulation, relative chlorophyll index, plant growth, and grain production were recorded. The inoculation of common bean plants with R. tropici and A. brasilense, and the co-inoculation improved leaf membrane stability and minimized the water loss from leaf tissue of plants under water stress conditions. Plants co-inoculated with R. tropici and A. brasilense had greater nodulation and relative chlorophyll index under severe drought stress. The inoculation with A. brasilense and the co-inoculation can attenuate the pod abortion rate of bean plants under moderate drought conditions but had no effect under severe stress conditions. Co-inoculation of A. brasilense and R. tropici alleviate the negative effects of water stress and maintain growth and grain yield of the common bean plants, and therefore, this management practice can be used by common bean farmers to enhance the plant tolerance to drought.

Cross-priming accentuates key biochemical and molecular indicators of defense and improves cold tolerance in chickpea (Cicer arietinum L.)

Cold environment favors long vegetative phase but also impose substantial loss by damaging reproductive functioning in chickpea. Field temperature below 10 °C is even more detrimental for reproductive development, enhances floral and pod abortion. In this study, contrasting chickpea varieties PDG3 and GPF2 were exposed to drought, recovered, and subsequently exposed to lethal cold stress ~ 4–5 °C with an aim to induce defense response against cold shock. Physiological, biochemical, and molecular signatures related to damage and defense, i.e., membrane damage, antioxidative enzymes, fatty acid desaturase (CaFAD2.1), and small HSPs (CaHSP18.5 and CaHSP22.7), were analyzed. Drought pretreatment/preconditioning maintained the membrane stability in the cold by managing malondialdehyde (MDA) content and lipoxygenase (LOX) activity. Improved mitochondrial functioning (TTC reduction), increased activity of catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) proved better cellular functioning during cold exposure. The expression and activity of superoxide dismutase (CaSOD) were down-regulated in both varieties, but CaCAT, CaAPX, CaGR, and CaFAD2.1 expressions were up-regulated in GPF2. Small heat shock protein CaHSP22.7 was also up-regulated in drought preconditioned PDG3 and GPF2 and after cold shock. Drought pretreatment/preconditioning significantly improved membrane damage during cold exposure, induced antioxidative system, and up-regulated FAD2. This study also pointed the possible role of CaHSP22.7 in cold tolerance and CaHSP18.5 in drought stress. The sensitive variety (GPF2) was positively responsive to preconditioning as this variety showed improvement in defense-related parameters; however, genotypic variations were observed in PDG3.

Reproductive development response to high daytime temperature in field pea

AbstractFlowering plants are highly sensitive to heat stress during reproductive phase, which covers development from floral initiation to seed maturity. The objectives of this study were to diagnose high temperature effects on pollen production and morphology, production of reactive oxygen species (ROS) in pollen grains and ovules in pea cultivar “CDC Golden.” This study also investigated timing and duration of heat exposure at specific developmental stages of floral buds, open flowers and early set pods on flower and pod abortion, seed development and seed yield in “CDC Golden” and a second cultivar “CDC Sage.” The experiments were conducted in growth chambers with two temperature regimes (24/18°C and 35/18°C day/night temperature for 4–14 days) during reproductive development. Heat stress reduced the number of pollen grains per anther, induced smaller pollen grains and increased ROS production in pollen grains, but it did not affect ROS accumulation in ovules and ovule number per ovary. Heat exposure when young floral buds were visible at the first reproductive node was more detrimental to flower retention, seed set, pod development and seed yield compared to heat exposure started later when flowers at the second reproductive node were fully open.

Can co-inoculation of Bradyrhizobium and Azospirillum alleviate adverse effects of drought stress on soybean (Glycine max L. Merrill.)?

Harnessing the beneficial potential of plant growth-promoting rhizobacteria may be an alternative strategy to improve plant tolerance to drought stress. The effect of inoculation with Bradyrhizobium japonicum and Azospirillum brasilense either alone or in combination on the plant growth and drought tolerance of soybean [Glycine max (L.) Merrill.] was investigated in this study in greenhouse conditions. Treatments were arranged in a randomized block design in a 3 × 4 factorial: three irrigation regimes [100% of pot capacity-PC (well-watered control), 50% of PC (moderate stress) and 25% of PC (severe stress)] and four inoculation treatments [control (non-inoculated), inoculation with B. japonicum, inoculation with A. brasilense, and co-inoculation with B. japonicum and A. brasilense]. Leaf relative water content, cell membrane stability, root nodulation, plant growth, and morphophysiological indexes were recorded. The inoculation of soybean plants with B. japonicum and A.brasilense either alone or in combination improved leaf membrane stability under drought stress conditions when compared to non-inoculated plants; however, this lower damage to cell membranes was not sufficient to maintain the leaf water content of the plant under drought stress. Plants co-inoculated with B. japonicum and A.brasilense improved the root nodulation under severe drought conditions. Inoculation of B. japonicum and A. brasilense either alone or in combination reduced the pod abortion rate under moderate drought stress, but had no effect under severe drought stress. In summary, the co-inoculation of A. brasilense and B. japonicum alleviate adverse effects limited by drought stress to the growth of soybeans.Author: Please check and confirm that the authors [Elijanara Raissa Silva, Carlos Eduardo Silva Oliveira, Alan Mario Zuffo, Eduardo Pradi Vendruscolo] and their initials have been correctly identified and amend if necessary.The authors were correctly identified.

Impact of Late‐Season Herbicide Applications on Winter Canola Yield and Seed Quality

Core Ideas The application of glyphosate during early reproductive growth resulted in significant declines in yield. Decreased yields with late‐season herbicides were associated with an increased number of aborted pods; however, this may not be the only factor contributing to the yield decline. Seed oil content followed the same general trend as grain yield, with decreased oil yields when glyphosate was applied during early reproductive growth. In canola (Brassica napus L.), control of grassy weeds can typically be achieved in the fall or spring with timely herbicide applications. However, environmental conditions can delay these applications into canola reproductive growth stages, which have an unknown effect on canola productivity. Therefore, a study was conducted to determine the impact of late‐season herbicide applications on canola grain yields and seed quality. The impact of three herbicides (glyphosate [N‐(phosphonomethyl)glycine], clethodim [(E)‐2‐[1‐[[3‐chloro‐2‐propenyl)oxy]imino]propyl]5=[2‐(ethylthio)propyl]‐2‐hydroxy‐2‐cyclohexen‐1‐one], and quizalofop‐P‐ethyl [Ethyl(R)‐2‐[4‐(6‐chloroquinoxalin‐2‐yloxy)‐phenoxy]propionate]) and three applications timings (bolting, early flower, and mid‐flower) were investigated on winter canola from 2015 through 2018 in Perkins and Stillwater, OK. Grain yields and pod abortion were collected at maturity. Subsamples of harvested seed were collected from each plot and used for oil analysis. When averaged across years, the application of glyphosate at bolting and early flower resulted in yield decreases of 531 and 488 kg ha–1 compared with the nontreated control. Yield following the application of clethodim at early flower resulted in a 185 kg ha–1 (2017) and 280 (2018) kg ha–1 decrease in yields compared with the control. Although yield decreases were observed following a few treatments, a significant increase in pod abortion was noted following many herbicide treatments, indicating that pod abortion was not the only factor contributing to yield declines. Decreases in oil content were only found following glyphosate applications at bolting and early flower. These results indicate that late‐season herbicide applications, especially glyphosate, should be avoided in winter canola.

Daily heliotropic movements assist gas exchange and productive responses in DREB1A soybean plants under drought stress in the greenhouse

Drought stress is one of the most severe environmental constraints on plant production. Under environmental pressures, complex daily heliotropic adjustments of leaflet angles in soybean can help to reduce transpiration losses by diminishing light interception (paraheliotropism), increase diurnal carbon gain in sparse canopies and reduce carbon gain in dense canopies by solar tracking (diaheliotropism). The plant materials studied were cultivar BR 16 and its genetically engineered isoline P58, ectopically overexpressing AtDREB1A, which is involved in abiotic stress responses. We aimed to follow the movements of central and lateral leaflets in vegetative stages V7-V10 and reproductive stages R4-R5, integrating the reversible morphogenetic changes into an estimate of daily plant photosynthesis using three-dimensional modeling, and to analyze the production parameters of BR 16 and P58. The patterns of daily movements of central leaflets of BR 16 in V7-V10 and R4-R5 were similar, expressing fewer diaheliotropic movements under drought stress than under non-limiting water conditions. Daily heliotropic patterns of lateral leaflets in V7-V10 and R4-R5 showed more diaheliotropic movements in drought-stressed P58 plants than in those grown under non-limiting water conditions. Leaf area in R4-R5 was generally higher in P58 than in BR 16. Drought significantly affected gas exchange and vegetative and reproductive architectural features. DREB1A could be involved in various responses to drought stress. Compared with the parental BR 16, P58 copes with drought through better compensation between diaheliotropic and paraheliotropic movements, finer tuning of water-use efficiency, a lower transpiration rate, higher leaf area and higher pod abortion to accomplish the maximum possible grain production under continued drought conditions.

The critical period for yield and quality determination in canola (Brassica napus L.)

Despite its global significance as an edible oil and biofuel, the critical period for yield determination in canola (edible oilseed rape – Brassica napus L.) has not been determined in the field. Field experiments were conducted at two contrasting sites in southern Australia where 100 °Cd shading periods (15% PAR transmitted) were applied from early vegetative growth until maturity to identify the developmental period when the crop was most sensitive to stress. Despite the significant difference between the two sites for yield in the unshaded control (450 g m−2 in New South Wales, and 340 g m−2 in South Australia), the critical period was consistent at both sites extending from 100 to 500 °Cd after the start of flowering (BBCH60), and centred 300 °Cd after BBCH60. Seed number (seed m−2) was reduced by an average of 48% in the critical period, generated in equal parts by reduced pod m−2 in the early part of the period, and reduced seed pod−1 in the latter part. Reduced seed number was partially compensated by an increase in seed size of 29%. These trends were similar on the branches and main stem. On the main stem, the timing of the critical period moved from earlier to later from lower to upper pods linked to the timing of their development. Seed oil content declined and protein content increased under shading in the critical period, while both oil and protein yield (kg m−2) were reduced by 40–50% and 30–40% respectively. The critical period is coincident with the greatest number of near-open buds and newly opened flowers, which are highly sensitive to assimilate supply for ovule development. Both pod abortion and restricted capacity for compensatory growth of surviving pods are consequences of assimilate restriction on developing ovules. Identification of the critical period provides a useful target for breeding and management strategies to maximize productivity.

First report of a ‘Candidatus Phytoplasma trifolii‘‐related strain associated with soybean bud proliferation and seed pod abortion in Iran

During a survey in 2016, soybean (Glycine max) plants in commercial fields in Mazandaran and Golestan provinces, Iran exhibited symptoms including bud proliferation and aborted seed pods, but showed no stunting or growth reduction (Fig. 1). Approximately 25% of plants were diseased. Leaf and pod samples were collected from five diseased plants from Golestan province and ten from Mazandarn province, and two asymptomatic plants were collected from a field without symptoms in Golestan province. Total genomic DNA was extracted using a CTAB-based method (Doyle & Doyle, 2). The DNA was used as template in direct PCR using the phytoplasma-universal primers P1/P7 (Ahrens & Seemuller, 1) designed to amplify the 16S ribosomal RNA gene, followed by nested PCR using the R16MF2/R16MR1 primers (Gundersen & Lee, 3). Reactions containing template DNA from all of the diseased plants yielded PCR products of the expected size (1,400 bp). All of the asymptomatic plants tested negative for phytoplasmas. Two isolates, one each from Golestan (SG7) and Mazandaran province (SG13), were sequenced directly using primers R16MF2/R16MR1 on both strands by Macrogen (Korea). The sequences of the two isolates were identical. Consensus nucleotide sequences of 1,250 bp were deposited in GenBank (Accession Nos. MG992479 and MG992480). A BLAST search revealed that the sequences shared 98% identity to rDNA of ‘Candidatus Phytoplasma trifolii’ (MF564268) associated with tomato disease in Turkey and ‘Ca. P. trifolii’ associated with a new disease in chilli pepper in Mexico. The new isolates (SG7 and SG13) associated with soybean bud proliferation and seed pod abortion (SBPSPA) disease have 98.24% sequence identity to the ‘Ca. P. trifolii’ reference strain (AY390261) and therefore represent a 'Ca. P. trifolii'-related strain. In a phylogenetic tree constructed using the neighbour joining algorithm, the SBPSPA phytoplasma obtained from soybean in Iran clustered with 'clover proliferation' group (16SrVI) strains. There are numerous reports of ‘Ca. P. trifolii’ in Iran, associated with cucumber and zucchini phyllody, salix proliferation and date yellows. There are reports of phytoplasmas in soybean including ‘Ca. P. asteris’ in the USA (Mollov et al., 5), and peanut witches' broom phytoplasma in Malawi and Mozambique (Lava et al., 4). To our knowledge, this is the first report of ‘Ca. P. trifolii’ in soybean worldwide.