Bio-primed Seeds Research Articles

Bacterial seed endophytes promote barley growth and inhibits Fusarium graminearum in vitro

ObjectivesSeeds host microbes that function in plant growth and phytopathogen resistance. The aim of the work was to investigate total bacterial community in malting barley seeds and whether their bacterial seed endophytes have dual functional roles in plant growth-promotion and inhibition of Fusarium graminearum, the causative agent of Fusarium head blight (FHB) in barley. We used culture dependent and culture independent methods.ResultsPhylogenetic classification of seed endophytic bacteria based on sequencing data identified B. subtilis, B. licheniformis and B. pumilis as predominant subgroups. Location driven divergence in bacterial endophytic communities was evident based on a clear separation of the samples from Crookston and other location samples. The bio-primed seeds using one hundred and seventy bacterial isolates showed that 3.5% (6/170) of the bacterial isolates conferred greater than 10% increase in both root length (RL) and shoot length (SL), while 19.4% (33/170) and 26.5% (45/170) showed RL and SL specific growth effects, respectively, relative to controls. Among the six bacterial isolates that increased RL and SL, five (#29, #63, #109, #124 and #126) also significantly inhibit the growth of F. graminearum based on in vitro assays. This study identified novel seed bacterial endophytes that could be further exploited for promoting growth during seedling establishment and as biocontrol for combating the devastating scab disease.

Biopriming using microbial consortia and biostimulants as a technique to increase seed quality of Solanum melongena L. by modifications in morphological and metabolic constituents

Brinjal (Solanum melongena L.) is a widely cultivated vegetable in tropical and subtropical regions. High-quality seeds are crucial for successful crop production, necessitating rapid and uniform field emergence. In the new wave of the Green Revolution, organic wastes were replaced by agrochemicals. This study was conducted from January to March 2024 to standardize biopriming techniques for brinjal using various organic inputs and microbial cultures to improve seed quality. Brinjal seeds cv. PLR 2 were treated with organic inputs (Panchagavya, Egg fermented extract, Fish fermented extract and effective microorganism solution) and liquid microbial cultures (Azospirillum and Pink Pigmented Facultative Methylotroph). The bioprimed seeds were assessed for their physiological attributes and anatomical and biochemical changes. Compared with the control, biopriming with 2% Fish fermented extract significantly improved the germination rate (19.4%), germination energy (40.9%), root length (44.4%), shoot length (24.4%) and seedling vigour index (68.1%). This increase was attributed to the nutritional and bioactive compounds in the fish by-products, which promoted root development and nutrient absorption. The biochemical parameters revealed increased ?-amylase activity, protein, and amino acid content in the bioprimed seeds. Gas Chromatography-Mass Spectrometry (GC-MS) analysis revealed beneficial root volatile compounds in the roots of treated seeds. An evaluation of the plant growth-promoting activities of the biopriming agents revealed the superiority of fish-fermented extract over other bioagents. Therefore, this method promotes sustainable agriculture and improved crop productivity, providing a scientific basis for biopriming as a viable alternative to conventional seed treatments.

Comparative Effect of Seed Coating and Biopriming of Bacillus aryabhattai Z-48 on Seedling Growth, Growth Promotion, and Suppression of Fusarium Wilt Disease of Tomato Plants.

Beneficial plant microbes can enhance the growth and quality of field crops. However, the benefits of microbes using cheap and efficient inoculation methods are still uncommon. Seed coating with biocontrol agents can reduce the amount of inocula along with having the potential for large-scale application. Hence, in this research work, the comparative potential of tomato seed coating and biopriming with Bacillus aryabhattai Z-48, harboring multiple plant-beneficial traits, to suppress Fusarium wilt disease along with its beneficial effect on seedling and plant growth promotion was analyzed. Among two bacterial strains, B. aryabhattai Z-48 was able to antagonize the mycelial growth of Fusarium oxysporum f.sp. lycopersici in vitro and its application as a seed coating superiorly benefited seedling traits like the germination percentage, vigor index, and seedling growth index along with a reduced germination time. The seed coating with B. aryabhattai Z-48 resulted in significant increases in the shoot length, root length, dry biomass, and total chlorophyll contents when compared with the bioprimed seeds with the same bacterial strain and non-inoculated control plants. The seed coating with B. aryabhattai Z-48 significantly reduced the disease index (>60%) compared with the pathogen control during pot trials. Additionally, the seed coating with B. aryabhattai Z-48 resulted in a significantly higher production of total phenolics, peroxidase, polyphenol oxidase, and phenylalanine ammonia lyase enzyme in tomato plants. The GC/MS-based non-targeted metabolic profiling indicated that the seed coating with B. aryabhattai Z-48 could cause large-scale metabolite perturbations in sugars, sugar alcohols, amino acids, and organic acids to increase the fitness of tomato plants against biotic stress. Our study indicates that a tomato seed coating with B. aryabhattai Z-48 can improve tomato growth and suppress Fusarium wilt disease effectively under conventional agricultural systems.

Seed Bio-priming of wheat with a novel bacterial strain to modulate drought stress in Daegu, South Korea.

Wheat is one of the major cereal crop grown food worldwide and, therefore, plays has a key role in alleviating the global hunger crisis. The effects of drought stress can reduces crop yields by up to 50% globally. The use of drought-tolerant bacteria for biopriming can improve crop yields by countering the negative effects of drought stress on crop plants. Seed biopriming can reinforce the cellular defense responses to stresses via the stress memory mechanism, that its activates the antioxidant system and induces phytohormone production. In the present study, bacterial strains were isolated from rhizospheric soil taken from around the Artemisia plant at Pohang Beach, located near Daegu, in the South Korea Republic of Korea. Seventy-three isolates were screened for their growth-promoting attributes and biochemical characteristics. Among them, the bacterial strain SH-8 was selected preferred based on its plant growth-promoting bacterial traits, which are as follows: abscisic acid (ABA) concentration = 1.08 ± 0.05 ng/mL, phosphate-solubilizing index = 4.14 ± 0.30, and sucrose production = 0.61 ± 0.13 mg/mL. The novel strain SH-8 demonstrated high tolerance oxidative stress. The antioxidant analysis also showed that SH-8 contained significantly higher levels of catalase (CAT), superoxide dismutase (SOD), and ascorbic peroxidase (APX). The present study also quantified and determined the effects of biopriming wheat (Triticum aestivum) seeds with the novel strain SH-8. SH-8 was highly effective in enhancing the drought tolerance of bioprimed seeds; their drought tolerance and germination potential (GP) were increased by up to 20% and 60%, respectively, compared with those in the control group. The lowest level of impact caused by drought stress and the highest germination potential, seed vigor index (SVI), and germination energy (GE) (90%, 2160, and 80%, respectively), were recorded for seeds bioprimed with with SH-8. These results show that SH-8 enhances drought stress tolerance by up to 20%. Our study suggests that the novel rhizospheric bacterium SH-8 (gene accession number OM535901) is a valuable biostimulant that improves drought stress tolerance in wheat plants and has the potential to be used as a biofertilizer under drought conditions.

Plant growth promotion and differential expression of defense genes in chilli pepper against Colletotrichum truncatum induced by Trichoderma asperellum and T. harzianum

BackgroundTrichoderma asperellum and T. harzianum were assessed in this study as a potential biological control against Colletotrichum truncatum. C. truncatum is a hemibiotrophic fungus that causes anthracnose disease in chilli thereby affecting plant growth and fruit yield. Scanning electron microscope (SEM) technique showed the beneficial interaction between chilli root-Trichoderma spp. inducing the plant growth promotion, mechanical barrier, and defense network under C. truncatum challenged conditions.MethodsSeeds bio-primed with T. asperellum, T. harzianum, and T. asperellum + T. harzianum promoted the plant growth parameters and strengthening of physical barrier via lignification on the wall of vascular tissues. Seed primed with bioagents were used for exploring the molecular mechanism of defense response in pepper against anthracnose to assess the temporal expression of six defense genes in the Surajmukhi variety of Capsicum annuum. QRT-PCR demonstrated induction of defense responsive genes in chilli pepper bioprimed with Trichoderma spp. such as plant defensin 1.2 (CaPDF1.2), superoxide dismutase (SOD), ascorbate peroxidase (APx), guaiacol peroxidase (GPx), pathogenesis related proteins PR-2 and PR-5.ResultsThe results showed that bioprimed seeds were assessed for T. asperellum, T. harzianum, and T. asperellum + T. harzianum-chilli root colonization interaction under in vivo conditions. The results of the scanning electron microscope revealed that T. asperellum, T. harzianum and T. asperellum + T. harzianum interact with chilli roots directly via the development of plant-Trichoderma interaction system. Seeds bio-primed with bioagents promoted the plant growth parameters, fresh and dry weight of shoot and root, plant height, leaf area index, number of leaves, stem diameter and strengthening of physical barrier via lignification on the wall of vascular tissues and expression of six defense related genes in pepper against anthracnose.ConclusionsApplication of T. asperellum and T. harzianum and in combination of treatments enhanced the plant growth. Further, as seeds bioprimed with T. asperellum, T. harzianum and in combination with treatment of T. asperellum + T. harzianum induced the strengthening of the cell wall by lignification and expression of six defense related genes CaPDF1.2, SOD, APx, GPx, PR-2 and PR-5 in pepper against C. truncatum. Our study contributed for better disease management through biopriming with T. asperellum, T. harzianum and T. asperellum + T. harzianum. The biopriming possess enormous potential to promote plant growth, modulate the physical barrier, and induced the defense related genes in chilli pepper against anthracnose.

Screening of Zinc Solubilizing Plant Growth Promoting Rhizobacteria (PGPR) as Potential Tool for Biofortification in Rice

Aims: Plant growth-promoting rhizobacteria enhance growth by making plant nutrients available to plants under a variety of growing conditions. The study was designed to screen zinc (Zn) solubilizing rhizobacteria and test their colonization ability in the rice rhizosphere.
 Place and Duration of Study: The experiments were conducted in the Department of Agricultural Chemistry, Bangladesh Agricultural University, Mymensingh-2202, from January 2019 to July 2019.
 Methodology: Initially, thirty-two previously isolated rhizobacteria were used for screening Zn solubilizing ability under a solid medium. Selected rhizobacteria from previous screening were used to quantify Zn solubilization in broth culture and evaluate their root colonization in rice using water agar media in a growth chamber. Early seedling growth was monitored for two weeks, and root-shoot lengths were recorded. Eleven of the tested rhizobacteria responded positively to ZnO-containing media.
 Results: The Zn solubilizing index (ZSI) of the positive isolates ranged between 1.08-2.25 after 5 days of incubation. Isolate MQ1 solubilized the highest Zn both in solid medium (ZSI=2.25) and culture broth (solubilized 220.20 ppm Zn). The colonization of bacteria in the root zone was also investigated via bio-primed rice seeds of Binadhan-20. Eight of 11 isolates (MQ1, MQ2, MQ3, MQ4, OSbr5, OSbr6, EC1, and MQL9) showed substantial colonization in the rhizosphere after two weeks. The germination percentage of bio-primed seeds was not increased over the control, however, in most cases, bio-priming boasted early seedling growth. The OSbr5, OSbr6, and MQ6 isolates were superior performers in case of root and shoot growth.
 Conclusion: The study identified some Zn solubilizing isolates, revealed their root colonizing ability, and observed early plant growth promotion. These isolates could be used as a potential tool for the Zn biofortification approach in rice.

Biopriming chilli seeds with Trichoderma asperellum: A study on biopolymer compatibility with seed and biocontrol agent for disease suppression

In this study, the biocontrol agent, Trichoderma asperellum, was bioprimed onto chilli seeds using several biopolymers (sodium alginate, carboxymethylcellulose, gum arabic, xanthan gum). T. asperellum showed >60 % growth inhibition towards Fusarium solani and Pythium ultimum, and is used subsequently for all tests. The compatibility of biopolymers to seed and T. asperellum, and the performance of the bioprimed seeds in tolerating disease is then assessed. Results showed that 1.5 % w:v sodium alginate (SA1.5) (imbibed for 1 h) has the highest compatibility with chilli seeds, with percentage of germination at 77.78 ± 4.44 %, seed vigour index at 320.79 ± 58.14 and germination rate at 1.27 ± 0.06. This treatment (SA1.5) also resulted in high coating efficacy, retaining 83.17 % of viable spores on chilli seeds and maintaining spore viability (4.08 ± 0.03 log spore/seed) after 24 h post-biopriming. SEM observations revealed high distribution of spores on chilli seeds with the use of SA1.5. With a treatment of just 102 spores/mL, the bioprimed seeds were able to suppress disease severity (DS) by F. solani in potted trials (27.33 ± 4.04 % DS). This is attributed to mycoparasitic properties of T. asperellum. Under F. solani infection, low proline level was recorded in bioprimed seedlings (0.94 ± 0.01 µmol/g fr. wt.) compared to non-bioprimed seedlings (5.05 ± 0.13 µmol/g fr. wt.), suggesting T. asperellum protected seedlings from pathogen. By contrast, the formulation of T. asperellum was less effective towards P. ultimum, as relatively high proline level (3.37 ± 0.05 µmol/g fr. wt.) and a lower total phenolic content (99.61 ± 4.29 mg GAE/100 g fr. wt.) were recorded. To conclude, our results revealed the compatibility of biopolymers, specifically sodium alginate with chilli seeds and T. asperellum, leading to enhanced efficacy in seed biopriming and seed tolerance to infection by F. solani.

Effects of seed biopriming with fungus Trichoderma harzianum on secondary metabolites production in cumin (Cuminum cyminum L.)

This study was aimed at investigating the effects of biopriming with a number of native isolates of Trichoderma harzianum on the germination and seed vigor indices of a native cumin (Cuminum cyminum L.) population. Also, the effects of extracellular enzymes produced by these isolates as elicitors on the production and accumulation of secondary metabolites in the seedlings obtained from bioprimed seeds were studied. Based on the results, all the T. harzianum isolates were able to produce the enzymes amylase, protease, cellulase, xylanase, chitinase, and lipase. The results also showed that the cumin seed biopriming significantly affected the germination and seed vigor indices and improved the quality and health of seeds and seedlings. In this study, the essential oil of seedlings obtained from the bioprimed seeds was extracted by water distillation and its chemical compounds were identified by GC and GC/MS. The results showed that the main compounds identified included β-pinene, ρ-cymene, limonene, γ-terpinene, terpinen-4-ol, α-terpineol, cuminaldehyde, and β-farnesene. Also, T. harzianum and the enzymes secreted by it as elicitors increased the expression of genes associated with the production and accumulation of secondary metabolites in cumin. This is the first report on the effects of seed biopriming with the native isolates of T. harzianum on the essential oil compounds of cumin seedlings. The findings of this research showed that the amount of extracellular enzymes secreted by the T. harzianum isolates is different and affects the production and accumulation of secondary metabolites in cumin.

Biopriming with Seaweed Extract and Microbial-Based Commercial Biostimulants Influences Seed Germination of Five Abelmoschus esculentus Genotypes.

Seed germination is a crucial step in plant propagation, as it controls seedling production, stand establishment and ultimately crop yield. Approaches that can promote seed germination of valuable crops remain of great interest globally. The current study evaluated the effect of biostimulant (Kelpak® and plant-growth-promoting rhizobacteria—PGPR) biopriming on the seed germination of five (VI037996, VI046567, VI055421, VI050956, and VI033796) Abelmoschus esculentus genotypes. The germination responses of the bio-primed seeds were measured using six parameters, including final germination percentage (FGP), mean germination time (MGT), germination index (GI), coefficient of velocity of germination (CVG), germination rate index (GRI), and time spread of germination (TSG). Biostimulant application significantly affected MGT (1.1–2.2 days), CVG (1.4–5.9), and TSG (1.2–3.0 days). Genotype also significantly influenced the TSG (1–3 days). Significant interaction effect of biostimulant treatment and genotype was evident on the FGP, GI, and GRI of the germinated seeds. The most noteworthy effect was demonstrated by Kelpak® (1:100) applied to genotype VI037996, with significantly improved FGP (82%), GI (238), and GRI (77%/day) when compared to the control. Overall, the current findings suggest the potential stimulatory effect of biostimulants (especially Kelpak®) on the germination of Abelmoschus esculentus seeds. However, this influence was strongly dependent on the type of genotype.

Seed biopriming with P- and K-solubilizing Enterobacter hormaechei sp. improves the early vegetative growth and the P and K uptake of okra (Abelmoschus esculentus) seedling.

Limited information is available that seed biopriming with plant growth-promoting Enterobacter spp. play a prominent role to enhance vegetative growth of plants. Contrary to Enterobacter cloacae, Enterobacter hormaechei is a less-studied counterpart despite its vast potential in plant growth-promotion mainly through the inorganic phosphorus (P) and potassium (K) solubilization abilities. To this end, 18 locally isolated bacterial pure cultures were screened and three strains showed high P- and K-solubilizing capabilities. Light microscopy, biochemical tests and 16S rRNA gene sequencing revealed that strains 15a1 and 40a were closely related to Enterobacter hormaechei while strain 38 was closely related to Enterobacter cloacae (Accession number: MN294583; MN294585; MN294584). All Enterobacter spp. shared common plant growth-promoting traits, namely nitrogen (N2) fixation, indole-3-acetic acid production and siderophore production. The strains 38 and 40a were able to produce gibberellic acid, while only strain 38 was able to secrete exopolysaccharide on agar. Under in vitro germination assay of okra (Abelmoschus esculentus) seeds, Enterobacter spp. significantly improved overall germination parameters and vigor index (19.6%) of seedlings. The efficacy of root colonization of Enterobacter spp. on the pre-treated seedling root tips was confirmed using Scanning Electron Microscopy (SEM). The pot experiment of bioprimed seeds of okra seedling showed significant improvement of the plant growth (> 28%) which corresponded to the increase of P and K uptakes (> 89%) as compared to the uninoculated control plants. The leaf surface area and the SPAD chlorophyll index of bioprimed plants were increased by up to 29% and 9% respectively. This report revealed that the under-explored species of P- and K-solubilizing Enterobacter hormaechei sp. with multiple plant beneficial traits presents a great potential sustainable approach for enhancement of soil fertility and P and K uptakes of plants.

Bacillus and Pseudomonas spp. strains induce a response in phenolic profile and enhance biosynthesis of antioxidant enzymes in Agrobacterium tumefaciens infected tomato plants

Some antagonistic bacteria contribute to the management of plant diseases by stimulating the host natural defense and/or by providing direct biocontrol of pathogens. The objective of this study was to evaluate the biocontrol performances and the ability to induce a systemic response to crown gall of four strains belonging to Bacillus and Pseudomonas genera. Evaluation of in vitro antagonistic ability showed that the four bacteria had a different spectrum of activity against the three tested strains of Agrobacterium tumefaciens. A delay in time of appearance and a significant reduction of the tumor size were observed in tomato plants obtained by bio-primed seeds and stem inoculated with A. tumefaciens. Seed priming with antagonistic strains stimulated some systemic defense mechanisms in tomato plants that can be related to the reduction of disease symptoms induced by A. tumefaciens. Both antagonists and A. tumefaciens strains induced variations in phenol content and peroxidase activity while polyphenol oxidase activity was mainly affected by the single A. tumefaciens strain. The response was different in relation to the various combinations of antagonist/pathogen, however Pseudomonas brassicacearum EPR3 strain was the most effective strain.

The integrated effect between phosphorus fertilizing levels and biological control on damping - off, root rot diseases and its reflection on an improving growth and fresh pods yield of priming and non-priming pea seeds

Two experiments were conducted in newly reclaimed soil for two successive winter seasons during 2014/2015 and 2015/2016 at El-Nobaria region, Beheira, Egypt on two peas cultivars, i. e. Little Marvel (LM) and Master B (MB). The purpose of this study is to improve the efficiency of biological seed treatments such as bio-priming and seed coating with T. harzianum in control of root rot disease and improve vegetative growth of pea plants under field conditions. In this investigation four levels of phosphorus were used, i.e. 0, 25, 50 and 75 kg P2O5 per fed. and combined with four biological seed treatments, i.e. untreated seeds (control); treated seeds with bio-priming, priming and coated by T. harzianum. Pea root rot disease incidence was recorded after 30 and 60 days of sowing. Results showed that the highest vegetative growth characters, total green pods yield and good quality were obtained by plants of Master P (MB) cultivar compared to Little Marvel (LM). The highest values of previous characters were recorded by plants which received 50 kg P2O5 / fed compared with other levels. Phosphorus fertilizer levels at 50 and 75 units/ fed were highly effective then 25 units/ feddan in decreasing the root rot % infection and reduction in the incidence of root rot of pea plants. Recommend by using pea seeds of cv. Master B in cultivation and using bio-primed seeds with bio-control agents like T. harzianum or T. viride or T. asperellum should be utilized for managing seed borne pathogens and fertilizing pea plants by adding mineral phosphorus fertilizer.

Effects of indigenous soil cyanobacteria on seed germination and seedling growth of arid species used in restoration

Cyanobacteria from biocrusts can enhance soil function and structure, a critical objective when restoring degraded dryland ecosystems. Large-scale restoration of biodiversity requires direct seeding of native plant species, and bio-priming seeds with cyanobacteria is a potential method of initiating enhanced soil functioning. The utility of cyanobacteria for improving soil is therefore dependent on whether target plant species remain unaffected during its application. Cyanobacteria from the genera Microcoleus and Nostoc were isolated from locally-sourced biocrust samples, and cultured under controlled conditions. A two-factor laboratory experiment was conducted including cyanobacteria and the culture growth medium (BG11) as factors. We bio-primed seeds of five species native to Western Australia, commonly used in dryland restoration, by soaking them in the cultures developed, and assessed germination and growth. We found significant positive effects of seeds bio-primed with cyanobacteria on germination and seedling growth of two species, Senna notabilis and Acacia hilliana, respectively. Importantly, no significant negative effects of cyanobacteria were found for any of the species studied. Few studies of cyanobacteria effects on regeneration of native species exist. We found that the potential benefits of applying indigenous bacteria via bio-priming seeds would not inhibit plant establishment, and indeed may be beneficial for some species used in dryland restoration.

Effect of Biopriming with Enterobacter Strains on Seed Germination and Seedling Growth of Tomato (Solanum lycopersicum L.) Under Osmotic Stress

A study was conducted to evaluate the effect of seed treatment with bacterial strains of Enterobacter spp. on seed germination and seedling growth of two tomato (Solanum lycopersicum L.) cultivars (cv. Arka Meghali and cv. Pusa Ruby). The cultivar Arka Meghali is recommended for rainfed conditions, while cv. Pusa Ruby is grown under irrigated conditions. Seeds were treated with osmotolerant plant growth promoting bacterial strains belonging to the genus Enterobacter (P-39, P-41 and P-46), for a period of 24 h and subsequently incubated at 25 °C under different mannitol induced osmotic stresses (0, −0.2, −0.4, −0.6, −0.8, −1.0 MPa). Seed treatment with bacterial strains influenced the germination and seedling vigour index of both cultivars as compared to the untreated and hydro-primed seeds, up to −0.6 MPa. The response of Enterobacter strains to water stress was better in cv. Pusa Ruby as compared to cv. Arka Meghali as indicated by higher germination percentage and germination rate. The seeds of both cultivars treated with Enterobacter P-39 performed better under osmotic stress (up to −0.6 MPa in cv. Arka Meghali and −0.8 MPa in cv. Pusa Ruby), indicating the significance of this strain as compared to other bacterial strains studied. The bioprimed seeds that failed to germinate at osmotic potentials beyond −0.4 MPa, when transferred to water (0 MPa), recorded improved germination and seedling vigour. These results indicated that the treatment of seeds with osmotolerant plant growth promoting bacterial strains improved the germination and enhanced seedling growth under osmotic stress conditions.

Field performance of bio-primed seeds to suppress Colletotrichum truncatum causing damping-off and seedling stand of soybean

The soybean is prone to be attacked by Colletotrichum truncatum at seed and seedling stages, resulting in pre- and post-emergence damping-off. The efficacy of bio-priming for the control of damping-off of soybean caused by C. truncatum and the final seedling stand using two fungal biocontrol agents (BCAs) Trichoderma harzianum and T. virens and one bacterial BCA Pseudomonas aeruginosa was evaluated under field conditions. Treatments consisted of chemo-primed with Benlate® as a positive control; bio-primed with P. aeruginosa; bio-primed with T. harzianum; bio-primed with T. virens; bio-primed with the mixture of T. virens and T. harzianum and the controls as hydro-primed and non-primed seeds. Trichoderma isolates used singly or as a mixture established on the seed surface with germinating hyphae, whereas the strain P. aeruginosa colonized profusely as determined by increased colony forming units (CFU) from 1.2 × 10 9 to 5.1 × 10 9 seed −1 after 12 h of bio-priming. All bio-priming treatments significantly reduced pre- and post-emergence damping-off relative to hydro- and non-primed seed controls. In general, bio-priming with P. aeruginosa was the most effective treatment for controlling pre and post-emergence damping-off, with reductions in disease incidence with increases ranging from 48.6% to 51.9% and 65.0% to 97.2%, respectively. Moreover, P. aeruginosa resulted in enhancement of seed germination and healthy seedling stand ranging from 32.4% to 60.0% and 56.0% to 73.9%, respectively. Bio-priming with T. harzianum reduced pre- and post-emergence damping-off by 42.8–46.8% and 35.0–85.1%, respectively. However, P. aeruginosa was generally comparable to T. harzianum and the fungicide Benlate®. The combination treatment of T. harzianum and T. virens produced compareable results to T. harzianum alone, and T. virens was the least effective of the bio-primed treatments. Bio-priming with P. aeruginosa or T. harzianum offered an effective biological seed treatment system and an alternative to the fungicide Benlate® for control of damping-off of soybean caused by C. truncatum of soybean.

Long-term activity of bio-priming seed treatment for biological control of faba bean root rot pathogens

The long-term activity of some antagonistic fungal and bacterial agents against the incidence of faba bean root rot incidence was evaluated when applied as a bio-priming seed treatment. The inhibitory effect of antagonistic fungi and bacteria against the linear growth of root rot pathogenic fungi was evaluated in vitro. The tested inhibitor factor in this study was the antagonistic agents applied as either growth culture discs or bio-primed faba bean seeds. The inhibitor effect of Trichoderma viride, T. harzianum, Bacillus subtilis and Pseudomonas fluorescens was significantly higher than T. hamatum and B. cereus, respectively. Similar results were also obtained when the antagonistic agents were applied as bio-primed seeds. Under greenhouse conditions, all the tested fresh and 2 months-stored, bio-primed faba bean seeds showed a highly significant effect causing complete reduction of root rot incidence at both pre — and post-emergence stages of plant growth compared with the control treatment. Stored seeds at 4 and 6 months showed a less protective effect against the incidence of disease. After 3 months of storage under field conditions, the antagonistic agents could protect seeds against infection by root rot pathogens at both pre- and post-emergence stages. However, after 6 months of storage, a lower protective effect was observed. No significance was observed between seeds primed only with adhesive agents and the untreated control. Promising applicable techniques could be suggested in light of the results obtained in the present study. The use of bio-primed seeds might be considered as a safe, cheap and easily applied biocontrol method against these soilborne plant pathogens.

FIELD PERFORMANCE OF BIO-PRIMING FOR PROTECTION OF sh2 SWEET CORN FROM PREEMERGENCE DAMPING-OFF CAUSED BY PYTHIUM ULTIMUM.

Shrunken-2 supersweet (sh2) sweet corn is susceptible to preemergence damping-off caused by Pythium ultimum, especially when planted into cold soil. Bio-priming, a seed treatment which combines the establishment of a bioprotectant on the seed with preplant seed hydration, was developed to protect seeds from damping-off.In a series of field experiments conducted in Montana's Bitterroot and Gallatin Valleys, bio-priming or seed bacterization with Pseudomonas fluorescens AB254 protected sweet corn from P. ultimum damping-off. Bio-priming corn seed with P. fluorescens AB254 was comparable to treatment with the fungicide metalaxyl in increasing seedling emergence. Seedlings from bio-primed seeds emerged from the soil more rapidly than from nontreated seeds and were larger at three weeks postplanting. Seeds of sh 2 and sugary enhancer (se) sweet corn, as well as that of several sh 2 cultivars, were protected from damping-off by bio-priming.