Characterization of plant growth-promoting traits of Penicillium species against the effects of high soil salinity and root disease

This study investigated the plant growth promotion and stress mitigation effects of Penicillium species RDA01, NICS01, and DFC01 on sesame (Sesamum indicum L.) plants. The fungal isolates NICS01 and DFC01 significantly enhanced shoot length, root length, and fresh and dry seedling weight, due to the secretion of various concentrations of amino acids (Asp, Thr, Ser, Asn, Glu, Gly, Ala, Val, Met, Ile, Leu, Tyr, Phe, Lys, His, Try, and Arg). Penicillium sp. NICS01 increased the amount of chlorophylls, proteins, amino acids, and lignans in the sesame plants more so than in controls. Sesame plant growth was stunted by high soil salinity, and application of the three fungal isolates increased plant survival. The RDA01 and NICS01 strains significantly increased shoot length and fresh and dry seedling weights under salt stress conditions. In addition, an in vitro study of the Penicillium spp. revealed their antagonistic activity toward the pathogenic fungi Fusarium spp. Fusarium spp. reduce shoot length; co-inoculation with the NICS01 or DFC01 isolates significantly increased shoot length in infected plants. Our results suggest that exogenous application of the Penicillium sp. NICS01 can act as a biofertilizer and a biocontrol agent to improve plant growth and enhance plant survival against salt stress and Fusarium infection.     

Effect of liquid seaweed extracts on growth of tomato seedlings (Solanum lycopersicum L.)

Seaweed extracts are used as nutrient supplements, biostimulants, or biofertilizers in agriculture and horticulture to increase plant growth and yield. In this study, we examined the effect of liquid seaweed extracts (LSEs) made from Ulva lactuca, Caulerpa sertularioides, Padina gymnospora, and Sargassum liebmannii as biostimulants on the germination and growth of tomato (Solanum lycopersicum) under laboratory and greenhouse conditions using foliar and soil drench applications of LSEs. We assessed LSEs at different concentrations (0.2, 0.4, and 1.0 %) on germination parameters (percentage, index, mean time, energy, and seedling vigor index) and growth parameters (plumule length, radical length, shoot length, root length, fresh weight, and dry weight) of tomato seedlings. Our results indicate that seeds treated with LSEs of U. lactuca and P. gymnospora at lower concentrations (0.2 %) showed enhanced germination (better response in germination rate associated with lower mean germination time, high germination index and germination energy, and consequently greater seedling vigor and greater plumule and radicle length). Application as a soil drench was found to be more effective in influencing the height of the plant (up to 79 cm) than the foliar spray application (75 cm). Plants receiving LSEs of U. lactuca and P. gymnospora showed increased shoot length, root length, and weight. Furthermore, U. lactuca and P. gymnospora were found to be more successful and better candidates for developing effective biostimulants to improve the growth of tomato plants. This study provides important information on the identification and utilization of Mexican seaweed resources for agriculture and is the first study to report on the uses of these seaweeds as a source of liquid extracts as biostimulants in agriculture.     

Effect of Seed Treatment with Rhizobium leguminosarum on Pythium Damping-off, Seedling Height, Root Nodulation, Root Biomass, Shoot Biomass, and Seed Yield of Pea and Lentil

Field experiments were conducted in 2004 and 2005 to determine the effects of seed treatment with Rhizobium leguminosarum bv. viceae on damping‐off, seedling height, root nodule mass, root biomass, shoot biomass and seed yield of pea and lentil in a field naturally infested with Pythium spp. Compared with the untreated controls, treatment of pea seeds with R. leguminosarum bv. viceae strains R12, R20 or R21 significantly (P < 0.05) reduced incidence of damping‐off, promoted seedling growth and increased root nodule mass, root biomass and shoot biomass. Seed treatments with R12 or R21 also resulted in a significant (P < 0.05) increase in seed yield of pea. The strain R21 was most effective among the four strains of R. leguminosarum bv. viceae tested in peas. Although, the level of disease control by strain R21 was similar to seed treatment with the fungicide Thiram^TM, R21 was more effective in enhancing root nodule production and promoting plant growth. For lentil, treatment of seeds with R. leguminosarum bv. viceae strains R12 or R21 significantly (P < 0.05) reduced incidence of damping‐off compared with the untreated control. All of the four strains of R. leguminosarum bv. viceae tested increased lentil seedling height, root nodule mass and shoot biomass, and all except R20 increased root biomass. Seed yield was higher for the treatments of R12 and R21. The strain R12 was most effective among the four strains of R. leguminosarum bv. viceae tested in lentil. Although, strain R12 was as effective as Thiram^TM for control of damping‐off of lentil, it was more effective than Thiram^TM for the production of root nodules and promotion of plant growth. The study concludes that seed treatment with R. leguminosarum bv. viceae is effective in control of Pythium damping‐off of pea and lentil and that the efficacy of control is strain specific, strain R21 for control of the disease on pea and strain R12 for control of the disease on lentil.     

Chilli rhizosphere fungus Aspergillus spp. PPA1 promotes vegetative growth of cucumber (Cucumis sativus) plants upon root colonisation

A rhizosphere fungus was isolated from roots of chilli plants and identified as Aspergillus spp. PPA1. The fungus was tested for its ability to promote the growth of cucumber plants in a pot experiment. Cucumber seeds were sown in sterilised field soil amended with wheat grain inoculum (WGI) of PPA 1 at the rate of 0.5, 1 and 1.5% w/w, and plants were grown for 21 days in a net house. The treatment with PPA1 significantly increased shoot length, shoot fresh weight, shoot dry weight, root length, root fresh weight, root dry weight, plant length, leaf area and leaf chlorophyll content of cucumber plants compared to non-treated control. The growth promotion rate increased with the increasing concentration of inoculum of PPA1 applied to the soil. The fungus was re-isolated from the roots of cucumber plants at higher frequencies. These results suggest that Aspergillus spp. PPA1 is a root colonising plant-growth promoting fungus for cucumber.     

Growth promotion effect of Fusarium spp. PPF1 from bermudagrass (Cynodon dactylon) rhizosphere on Indian spinach (Basella alba) seedlings are linked to root colonisation

A rhizosphere fungus was isolated from roots of bermudagrass (Cynodon dactylon) and identified as Fusarium spp. PPF1. A pot experiment was conducted to test its ability to promote the vegetative growth of Indian spinach seedlings (Basella alba). Indian spinach seeds were sown in sterilised field soil amended with wheat grain inoculum of PPF1 at the rate of 0.5 and 1.0% w/w, and plants were grown for 21?days in a net house. Significantly, higher germination percentage and vigour index were observed due to application of PPF1 in the potting soil. Treatment with PPF1 also significantly increased shoot length, shoot fresh weight, shoot dry weight, root length, root fresh weight, root dry weight, leaf area and leaf chlorophyll content of cucumber plants compared to non-treated control. The growth promotion rate increased with the increasing concentration of inoculum of PPF1 applied to the soil. The fungus was re-isolated from the roots of cucumber plants at higher frequencies, while a positive co-relation was found between the root colonisation ability and the plant growth enhancement by the isolate. These results suggest that growth promotion effect of Fusarium spp. PPF1 on Indian spinach (B. alba) are linked to root colonisation ability of the fungus.     

ACC-deaminase and/or nitrogen-fixing rhizobacteria and growth response of tomato (Lycopersicon pimpinellfolium Mill.)

The study aimed to identify and select important plant growth-promoting rhizobacteria (PGPR) and examine the response of tomato growth upon inoculation. Inoculation with rhizobacterial isolates increased all the measured physical, chemical, and enzymatic growth parameters compared to control. However, the TAN1 isolate had the highest effect, and significantly (P < 0.05) increased the root length (8.25-fold), root fresh (8.36-fold) and dry (12.6-fold) weight, shoot length (6.92-fold), shoot fresh (7.18-fold) and dry (6.90-fold) weight, number of leaves (11.0-fold), chlorophyll a (6.25-fold), chlorophyll b (10.7-fold), carotenoid contents (8.80-fold), seedlings fresh (9.0-fold) and dry (8.71-fold) weight, plant macronutrient uptake, i.e. N (7.7- and 8.9-fold), P (10.5- and 11.4-fold), K (7.8- and 8.8-fold), Ca (12.7- and 8.2-fold), and Mg (12.6- and 9-fold) in shoot and root, plant micronutrient uptake, i.e. Zn (6.6-, 10.2-), Cu (9.3-, and 10.3-fold), Fe (7.7- and 10.7-fold), and Mn (4.7- and 5.7-fold) in shoot and root and plant antioxidant enzymes, i.e. glutathione S-transferase (10.7-fold), peroxidase (8.1-fold), and catalase (10.5-fold). Our results concluded that inoculation of agricultural crops with rhizobacteria is a very useful approach to increase the plant growth. The rhizobacteria having both 1-aminocyclopropane-1-carboxylate (ACC) deaminase and nitrogen-fixing activity are more effective than rhizobacteria possessing either ACC-deaminase or nitrogen-fixing activity alone for growth promotion of crops.     

Growth of canola (Brassica napus) in the presence of plant growth-promoting bacteria and either copper or polycyclic aromatic hydrocarbons

Growth of canola (Brassica napus) seeds treated with plant growth-promoting bacteria in copper-contaminated and polycyclic aromatic hydrocarbon (PAH)-contaminated soils was monitored. Pseudomonas asplenii AC, isolated from PAH-contaminated soil, was transformed to express a bacterial gene encoding 1-aminocyclopropane-1-carboxylate (ACC) deaminase, and both native and transformed bacteria were tested for growth promotion. Inoculation of seeds, grown in the presence of copper or creosote, with either native or transformed P. asplenii AC significantly increased root and shoot biomass. Native and transformed P. asplenii AC and transformed P. asplenii AC encapsulated in alginate were equally effective at promoting plant growth in copper-contaminated soils. In creosote-contaminated soils the native bacterium was the least effective, and the transformed encapsulated bacterium was the most effective in growth promotion.     

Molecular characterization of plant growth promoting rhizobacteria that enhance peroxidase and phenylalanine ammonia-lyase activities in chile (<Emphasis Type="Italic">Capsicum annuum</Emphasis> L.) and tomato (<Emphasis Type="Italic">Lycopersicon esculentum</Emphasis> Mill.)

Pythium and Phytophthora species are associated with damping-off diseases in vegetable nurseries and reduce seedling stand and yield. In this study, bacterial isolates were selected on the basis of in vitro antagonism potential to inhibit mycelial growth of damping-off pathogens along with plant growth properties for field assessment in wet and winter seasons. We demonstrate efficacy of bacterial isolates to protect chile and tomato plants under natural vegetable nursery and artificially created pathogen-infested (Pythium and Phytophthora spp.) nursery conditions. After 21 days of sowing, chile and tomato plants were harvested and analysed for peroxidase and phenylalanine ammonia-lyase activities. Pseudomonas sp. strains FQP PB-3, FQA PB-3 and GRP₃ were most effective in increasing shoot length (P > 0.05%) in both artificial and natural field sites. For example, Pseudomonas sp. FQA PB-3 treatment increased shoot length by 40% in the artificial Pythium 4746 infested nursery site in chile plants in the wet season. The bacterial treatments significantly increased the activity of peroxidase and phenylalanine ammonia-lyase in chile and tomato plant tissues, which are well known as indicators of an active lignification process. Thus, we conclude that treatment with potential bacterial plant growth promoting agents help plants against pathogen invasion by modulating plant peroxidase and phenylalanine ammonia-lyase activities.     

Development of formulations based on Streptomyces rochei strain PTL2 spores for biocontrol of Rhizoctonia solani damping-off of tomato seedlings

Rhizoctonia solani is one of the most problematic soil-borne pathogenic fungi for several crop cultures worldwide. This study highlights the effectiveness of high-antagonistic Streptomyces rochei strain PTL2, isolated from root tissues of Panicum turgidum, in controlling the R. solani damping-off and growth promotion of tomato (cv. Marmande) seedlings. The isolate PTL2 was characterised for in vitro biocontrol and plant growth-promoting traits. It exhibited remarkable positive results in all trials, including production of hydrogen cyanide, siderophores, 1-aminocyclopropane-1-carboxylate deaminase and phytohormones, chitinolytic activity and inorganic phosphate solubilisation. PTL2 spores were formulated as wettable talcum powder, sodium alginate pellets and sodium alginate-clay pellets. Their abilities in the biocontrol of R. solani and plant growth promotion were investigated in autoclaved and non-autoclaved soils. Talcum powder and sodium alginate pellets significantly reduced the damping-off severity index compared to a positive control. The talcum powder exhibited the highest protective activity, reducing the disease incidence from 89.3% to 14.1%, whereas chemical seed treatment with Thiram^® provided a disease incidence of 16.7%. Furthermore, the talc-based powder formulation resulted in greatest increases in the root length, shoot length and dry weight of seedlings. The interesting biocontrol potential and growth enhancement of tomato seedlings open up promising perspectives for the possible application of talcum powder formulation based on PTL2 spores in crop improvement.     

Der Besatz von Beta-Rüubensaatgut rait Wurzelbranderregern und der Einfluß von Umweltfaktoren auf das Auftreten des samenbüurtigen Wurzelbrandes

The root knot nematode Meloidogyne incognita was controlled more effectively when P. lilacinus and G. mosseae were applied together in a pot experiment than either was applied alone. Inoculation of tomato plant with G. mosseae did not markedly increase the growth of plant infected with M. incognita. Inoculation of plant with G. mosseae and P. lilacinus together or alone resulted in a similar shoot and plant height. The highest root development was achieved when mycorrhizal plant were inoculated with P. lilacinus to combat root knot nematode. Inoculation of tomato plant with P. lilacinus suppressed galls/root system and eggs/egg masses, compared to seedling inoculated with M. incognita alone. The mycorrhizal colonization was not affected by inoculation of P. lilacinus.     

番茄根内促生放线菌的分离鉴定及其促生效果

【背景】植物体内普遍存在一定数量的内生放线菌,对植物的生长发育具有促生作用。【目的】从番茄根内分离、筛选并鉴定出能够有效促进植物生长发育的内生放线菌,为生物菌肥的开发奠定基础。【方法】采用组织研磨培养法和放线菌分离培养基对番茄根内放线菌进行分离,利用Salkowski比色法、钼锑抗比色法和CAS平板检测法进一步筛选出具有较强促生特性的菌株,通过番茄和黄瓜苗期盆栽试验验证其促生效果。结合形态、生理生化以及16S r RNA基因序列相似性和系统发育分析,对菌株进行鉴定。【结果】分离筛选出一株吲哚乙酸(Indole-3-acetic acid,IAA)产量达25.56 mg/L的内生放线菌NEAU-D1,能够产生铁载体并且对多种难溶性磷酸盐具有良好溶解效果,通过16S r RNA基因序列分析,该菌株属链霉菌属。番茄和黄瓜苗期盆栽试验结果表明,接种该菌株的番茄幼苗其根长、株高、植株鲜重和干重较对照分别显著增加了9%、23%、47%和92%,而接种该菌株的黄瓜幼苗根长、株高、植株鲜重和干重较对照分别显著增加了43%、47%、134%和58%。【结论】链霉菌NEAU-D1可以作为潜在的促生菌资源用于设施蔬菜多功能生物菌肥的研发。     

Isolation of micropropagated strawberry endophytic bacteria and assessment of their potential for plant growth promotion

Twenty endophytic bacteria were isolated from the meristematic tissues of three varieties of strawberry cultivated in vitro, and further identified, by FAME profile, into the genera Bacillus and Sphingopyxis. The strains were also characterized according to indole acetic acid production, phosphate solubilization and potential for plant growth promotion. Results showed that 15 strains produced high levels of IAA and all 20 showed potential for solubilizing inorganic phosphate. Plant growth promotion evaluated under greenhouse conditions revealed the ability of the strains to enhance the root number, length and dry weight and also the leaf number, petiole length and dry weight of the aerial portion. Seven Bacillus spp. strains promoted root development and one strain of Sphingopyxis sp. promoted the development of plant shoots. The plant growth promotion showed to be correlated to IAA production and phosphate solubilization. The data also suggested that bacterial effects could potentially be harnessed to promote plant growth during seedling acclimatization in strawberry.     

Mitigation of growth retardation effect of plant defense activator,acibenzolar-<Emphasis Type="Italic">S</Emphasis>-methyl,in amaranthus plants by plant growth-promoting rhizobacteria

Four rhizobacterial strains and acibenzolar-S-methyl (ASM), a chemical activator, which suppressed foliar blight of amaranthus (Amaranthus tricolor L.) caused by Rhizoctonia solani Kühn were evaluated for their effect on plant growth. The experiments were performed both under sterile and non-sterile soil conditions, in the presence or absence of the pathogen. In all cases, plants treated with ASM showed significant reduction in growth, as determined by shoot length, and shoot and root dry weight when compared to other treatments. The growth retardation effect of ASM was more profound with respect to shoot length. Reduction in shoot length was least when plants were treated with a combination of the chemical activator and Pseudomonas putida 89B61 under non-sterile soil conditions in the absence of the pathogen. Both under sterile and non-sterile soil conditions, in the presence of the pathogen, reduction in shoot length due to application of ASM was diminished significantly when plants were treated with rhizobacterial strain Pseudomonas fluorescens PN026R. Combined use of plant growth-promoting rhizobacteria (PGPR) and ASM was found to be beneficial as the growth retardation effect of the plant defense activator was reduced by the growth-promoting ability of the rhizobacteria.     

田菁根际促生菌的筛选及其促生耐盐效果

【目的】为探究盐生植物田菁及其根际功能微生物改良盐碱地的效果,本研究从黄河三角洲盐碱区田菁根际土壤中分离促生菌,并明确其耐盐促生效果。【方法】采用选择培养方法从田菁根际土壤中分离固氮菌、解磷菌以及解钾菌,并进行16S rRNA分子生物学鉴定。之后对菌株的耐盐及促生特性进行测定,筛选性状优良菌株进行玉米促生作用研究。【结果】共分离得到105株根际促生菌,其中N102兼具多种促生特性且耐盐性达15%。田菁种子发芽试验表明,N102可显著提高田菁发芽率(47%,P0.05)、芽长(48.5%,P0.05)和根长(60%,P0.05);玉米盆栽试验结果表明,N102对盐胁迫下玉米的株高、根长、叶绿素含量、地上部干重以及根干重具有显著的促进作用。经系统发育分析,N102与Enterobacter soli ATCC BAA-2102 (NR117547)序列相似度为99.30%,鉴定属于Enterobacter属。【结论】菌株N102具有多种植物促生耐盐特性,具有开发成有效促进盐碱地作物生长的微生物肥的良好前景。     

Azospirillum sp. Promotes Root Hair Development in Tomato Plants through a Mechanism that Involves Ethylene

Tomato seeds were inoculated with the plant growth–promoting rhizobacteria Azospirillum brasilense FT326, and changes in parameters associated with plant growth were evaluated 15 days after inoculation. Azospirilla were localized on roots and within xylematic tissue. An increase in shoot and root fresh weight, main root hair length, and root surface indicated that inoculation with A. brasilense FT 326 resulted in plant growth improvement. The levels of indole-3-acetic acid (IAA) and ethylene, two of the phytohormones related to plant growth, were higher in inoculated plants. Exogenously supplied ethylene mimicked the effect of inoculation, and the addition of an inhibitor of its synthesis or of its physiological activity completely blocked A. brasilense growth promotion. Based on our results, we propose that the process of growth promotion triggered by A. brasilense inoculation involves a signaling pathway that has ethylene as a central, positive regulator.     

Root growth dynamics of Aleppo pine (Pinus halepensis Mill.) seedlings in relation to shoot elongation, plant size and tissue nitrogen concentration

Large and high nitrogen (N) concentration seedlings frequently have higher survival and growth in Mediterranean forest plantations than seedlings with the opposite traits, which has been linked to the production of deeper and larger root systems in the former type of seedlings. This study assessed the influence of seedling size and N concentration on root growth dynamics and its relation to shoot elongation in Aleppo pine (Pinus halepensis Mill.) seedlings. We cultivated seedlings that differed in size and tissue N concentration that were subsequently transplanted into transparent methacrylate tubes in the field. The number of roots, root depth, and the root and shoot elongation rate (length increase per unit time) were periodically measured for 10 weeks. At the end of the study, we also measured the twig water potential (ψ) and the mass of plant organs. New root mass at the end of the study increased with seedling size, which was linked to the production of a greater number of new roots of lower specific length rather than to higher elongation rate of individual roots. Neither plant size nor N concentration affected root depth. New root mass per leaf mass unit, shoot elongation rate, and pre-dawn ψ were reduced with reduction in seedling size, while mid-day ψ and the root relative growth rate were not affected by seedling size. N concentration had an additive effect on plant size on root growth but its overall effect was less important than seedling size. Shoot and roots had an antagonistic elongation pattern through time in small seedlings, indicating that the growth of both organs depressed each other and that they competed for the same resources. Antagonism between shoot and root elongation decreased with plant size, disappearing in large and medium seedlings, and it was independent of seedling N concentration. We conclude that root and shoot growth but not rooting depth increased with plant size and tissue N concentration in Aleppo pine seedlings. Since production of new roots is critical for the establishment of planted seedlings, higher absolute root growth in large seedlings may increase their transplanting performance relative to small seedlings. The lack of antagonism between root and shoot growth in large seedlings suggests that these plants can provide resources to sustain simultaneous growth of both organs.     

Effect of an AM fungal consortium and Pseudomonas on the growth and nutrient uptake of Eucalyptus hybrid

 Eucalyptus is an important tree species used for afforestation of large tracts of marginal and wastelands. Eucalyptus-arbuscular mycorrhizal fungal (AMF) interactions in seedling establishment and growth promotion have been inadequately dealt with. Efforts were made to assess the role of AMF-pseudomonad (PRS9, plant growth promotory fluorescent Pseudomonas) interactions in growth promotion and nursery establishment of E. hybrid. Seedlings were subjected to six different treatments: (i) uninoculated control, (ii) 400 AM spores, (iii) 800 AMF spores, (iv) PRS9 (v) 400 AMF spores + PRS9, (vi) 800 AMF spores + PRS9, with the different P regimes of 10, 20 and 30 ppm. Root length, shoot length, root and shoot fresh and dry weights were maximal at 400 AMF spores and 20 ppm soil P. Shoot P content was maximal at 800 AMF spores followed by 400 AMF spores and 400 AMF spores + PRS9. In general, plant growth was greater at 20 ppm P. Root P content increased significantly with 400 AMF spores followed by 800 at 20 ppm P. Independent of soil P levels, the quality index of mycorrhizal treatments without PRS9 was significantly higher than the treatments including PRS9 or PRS9 alone. Mycorrhizal inoculation efficiency was superior at 10 ppm P irrespective of the treatment. AM alone (400 spores) significantly improved the inoculation efficiency. PRS9 in association with AM fungi inhibited growth promotion and nutrient uptake Accepted: 8 September 1999     

Disease suppression and crop improvement in moong beans (<Emphasis Type="Italic">Vigna radiata</Emphasis>) through <Emphasis Type="Italic">Pseudomonas</Emphasis> and <Emphasis Type="Italic">Burkholderia</Emphasis> strains isolated from semi arid region of Rajasthan,India

Pseudomonas fluorescens BAM-4, Burkholderia cepacia BAM-6 and B. cepacia BAM-12 isolated from the rhizosphere of moong bean (Vigna radiata L.) showed significant growth-inhibitory activity against a range of phytopathogenic fungi. Light and scanning electron microscopic (SEM) studies showed morphological abnormalities such as fragmentation, swelling, perforation and lysis of hyphae of pathogens by Pseudomonas and Burkholderia. Two of the strains (BAM-4 and BAM-6) produced siderophore in CAS agar plates, whereas all three strains produced chitinase. Bacterization of seeds of moong bean with pseudomonads has been reported as a potential method for enhancing plant growth and yield, and for providing protection against Macrophomina phaseolina. Seed bacterization with these plant growth-promoting rhizobacteria (PGPR) showed a significant increase in seed germination, shoot length, shoot fresh and dry weight, root length, root fresh and dry weight, leaf area and rhizosphere colonization. Yield parameters such as pods, number of seeds, and grain yield per plant also enhanced significantly in comparison to control. The disease suppression and plant growth enhancement along with the positive rhizosphere colonization by these strains indicate their possible use as PGPR/biocontrol agents against charcoal rot.     

Tomato growth and resistance promotion by Enterobacter hormaechei subsp. steigerwaltii EB8D

Fusarium wilt is an economically important disease of tomato crop (Solanum lycopersicum L). Plant growth-promoting rhizobacteria (PGPR) represent an alternative to improve plant growth and yield as well as to act as agent of biocontrol. In this study, antagonistic effects of four selected isolates (EB8D, EB20J, EB24L and EB26M) were evaluated against Fusarium oxysporum f.sp. radicis lycopersici (FORL) as potential biocontrol agents in vitro and in vivo. After 30?days of culture, dry weight, length of stem and root were significantly (p?≤?.05) higher compared with the non-inoculated control. Compared with the control plate (inoculated only with pathogen), EB8D had showed efficient antagonism against FORL (48.88%). The different strains have been screened for siderophore production, solubilisation of mineral phosphates, synthesis of indolic acetic acid (IAA) to show the plant growth-promoting potential. The experimental groups were compared with a control group that did not receive any treatment by FORL, and EB8D was the best isolate in terms of growth promotion with an improvement of 73.85% of the stem length, 110.86% of the root length and 118.85% of the dry weight comparing with the non-treated controls. Compared with a control group treated by FORL, biocontrol activity has shown that EB8D strain improved the stem length with 111.85%, the root length with 118.85% and the dry weight with 452.38%. 16S rRNA analysis has confirmed that this strain belongs to the genus Enterobacter and has high similarity with Enterobacter hormaechei subsp. steigerwaltii (99.71%). EB8D has a significant strong protective potential against FORL and lead to better tomato growth and might have biotechnological potential for controlling fusarium wilt in tomato plants.     

Biopriming of maize seeds with plant growth-promoting bacteria isolated from the earthworm Aporrectodea molleri: effect on seed germination and seedling growth

Earthworms have become a potential source of multi-beneficial bacteria and effective bioinoculants. Seed biopriming is an efficient inoculation method to apply bacteria prior to sowing, which enhances the chances of bacterial candidates to colonize the rhizosphere and/or establish a liaison with the plant. In this study, we evaluated plant growth-promoting traits of bacterial strains isolated from the earthworm’s Aporrectodea molleri chloragogenous tissue. In addition, we investigated their prospective use as biopriming agents to enhance Zea mays germination and seedling growth. Results were subjected to principal component analysis for potential correlations between the studied parameters. The bacterial strains displayed different in vitro plant growth-promoting characteristics and were efficient when applied in vivo as they significantly increased maize germination rate (26–78%), root elongation (67–84%), seedlings fresh weight and dry weight. Aeromonas encheleia TC22 was the most significant strain to influence germination due to its high ability to produce indole-3-acetic acid, and along with Pseudomonas azotoformans TC1, they were the most proficient at enhancing seedling root elongation and biomass, which was significantly correlated with their in vitro plant growth-promoting traits. Our findings indicate that isolates TC22 and TC1 are potent bio-primers for maize seeds and should be tested further for their use as biopriming inoculants.