Tomato Growth Promotion Research Articles

Potential of a novel endophytic Bacillus velezensis in tomato growth promotion and protection against Verticillium wilt disease

Vascular wilts are one of the major threats to the growth and the productivity of crop plants. Repeated use of chemical fungicides to manage vascular wilt diseases are raising concerns. Other strategies including biocontrol using endophytic bacteria have been considered. To investigate the role of endophytic bacteria on Verticillium wilt, a novel bacterium C2, isolated from the crown tissue of tomato, was evaluated, in vitro and in vivo, against tomato wilt disease caused by Verticillium dahliae. C2 was identified by 16S rRNA gene sequencing as Bacillus velezensis. This strain exhibited, in vitro, significant antifungal activity against V. dahliae. This strain harbored genes involved in synthesis of lipopeptides (bacillomycin, fengycin and surfactin), polyketides (macrolactin, bacillaene and difficidin) and the dipeptide bacilysin. Moreover, GC–MS analysis of C2 showed the presence of volatile metabolites known by their antifungal activity, namely tetradecane, benzeneacetic acid, benzaldehyde, 1-decene and phenylethyl alcohol. Furthermore, the strain was able to produce lytic enzymes (protease, chitinase and β-glucanase), siderophore and indole-3-acetic acid and to solubilize inorganic phosphate. Result of in vivo experiments indicated that the application of C2 at 107 CFU/mL, reduced significantly the Verticillium wilt incidence in tomato plant by 70.43 ± 7.08%, compared to the untreated control. Besides protection, C2 improved markedly tomato plant growth which was evidenced by stem elongation and leaves number. The overall results of this study showed that B. velezensis C2 has a great potential to be commercialized as a biostimulant and biocontrol agent to manage effectively tomato Verticillium wilt disease.

Endophytic bacteria of desert cactus (Euphorbia trigonas Mill) confer drought tolerance and induce growth promotion in tomato (Solanum lycopersicum L.)

Endophytic bacteria isolated from cactus were characterized and assessed for their capability to induce drought tolerance and growth promotion in tomato. A total of 191-bacteria representing 13-genera and 18-species were isolated from wild cactus, Euphorbia trigonas. Bacillus (58), Lysinibacillus (36), Enterobacter (29), Stenotrophomonas (18), Lelliottia (12) and Pseudomonas (12) were the most represented genera. 16S rDNA sequence (>1400-bp) comparison placed the bacterial isolates with Bacillus xiamenensis; Bacillus megaterium; Bacillus cereus; Bacillus amyloliquefaciens; Bacillus velezensis; Brevibacillus brevis; Lysinibacillus fusiformis; Enterobacter cloacae; Lelliottia nimipressuralis; Proteus penneri; Sphingobacterium multivorum; Klebsiella pneumoniae; Pseudomonas putida; Pseudomonas aeruginosa; Stenotrophomonas maltophilia; Citrobacter freundii; Chryseobacterium indologenes and Paracoccus sp. Bacillus xiamenensis was identified for the first time as plant endophyte. Upon bacterization, the endophytes triggered germination and growth promotion in tomato as indicated by 118 % and 52 % more root-biomass under drought-free and drought-induced conditions, respectively. Bacillus amyloliquefaciens CBa_RA37 and B. megaterium RR10 displayed broad spectrum endophytism in tomato. Bacterization of tomato with cactus endophyte showed altered oxidative status, stomatal and photosystem II functioning, internal leaf temperature and relative water content suggestive of physiological de-stressing from moisture stress. Activity of oxidative stress enzymes such as guaiacol peroxidase and catalase was also indicative of endophyte assisted de-stressing of tomato. Re-irrigation on 20-days of drought infliction showed 86.9% recovery of B. amyloliquefaciens CBa_RA37 primed tomato when non-primed plantlets succumbed. The cactus endophytic bacterial strain B. amyloliquefaciens CBa_RA37 showed promise for low-cost, efficient and environmentally friendly bio-inoculant technology to mitigate drought in arid zones of Asian and African continents.

Effect of Bacillus subtilis on Meloidogyne javanica and on Tomato Growth Promotion

Objective: To evaluate under controlled conditions the effect of alternative liquid Bacillus subtilis isolate 34 formulation on Meloidogyne javanica and tomato growth promotion.
 Statistical Design: The design was completely randomized block with five treatments and eight replicates. The results were submitted to the analysis of variance and the averages compared by the Tukey test with 5% error probability. The statistical package used in the analysis of the data was the program "Sisvar"
 Location and Duration of the Experiment: The experiment was set up during the period from February 13, 2018 to April 20, 2018 in greenhouse located at the State University of Montes Claros, municipality of Janaúba, MG, Brazil.
 Methods: Treatments consisted of different times of application of bacteria in tomato seedlings: application of bacteria in the tube at eight and fifteen days after emergence; application of bacteria in the tube at eight and fifteen days after emergence and in pots at 25 and 35 days after transplanting; application of bacteria at 25 and 35 days after transplantation in the pot; Onix® commercial product (Bacillus methylotrophicus-UFPEDA20) and control. After 60 days of transplanting, the number of egg masses, number of galls, number of eggs, number of second-stage juveniles (J2) and reproduction factor, height, fresh and dry shoot mass and fresh root mass of tomato plants were evaluated.
 Results: There was a reduction in the number of J2, eggs pre root, and eggs per gram of root when the bacteria formulation was applied in the tube + pot and in pot only. The application of the bacteria in the tube + pot and in only pot only presents the highest increase of fresh and dry shoot mass and fresh root mass.
 Conclusion: The application of the liquid B. subtilis isolated 34 formulation to the soil in the pot and tube + pot reduced the reproduction of M. javanica and promoted greater tomato development.

Ability of endophytic fungi associated with Withania somnifera L. to control Fusarium Crown and Root Rot and to promote growth in tomato

Fusarium crown and root rot (FCRR), caused by Fusarium oxysporum f. sp. radicis-lycopersici (FORL), is a soilborne tomato disease of increased importance worldwide. In this study, Withania somnifera was used as a potential source of biological control and growth-promoting agents. Seven fungal isolates naturally associated with W. somnifera were able to colonize tomato seedlings. They were applied as conidial suspensions or a cell-free culture filtrate. All isolates enhanced treated tomato growth parameters by 21.5-90.3% over FORL-free control and by 27.6-93.5% over pathogen-inoculated control. All tested isolates significantly decreased by 28.5-86.4% disease severity over FORL-inoculated control. The highest disease suppression, by 86.4-92.8% over control and by 81.3-88.8% over hymexazol-treated control, was achieved by the I6 isolate. FORL radial growth was suppressed by 58.5-82.3% versus control when dual cultured with tested isolates and by 61.8-83.2% using their cell-free culture filtrates. The most active agent was identified as Fusarium sp. I6 (MG835371), which displayed chitinolytic, proteolytic, and amylase activities. This has been the first report on the potential use of fungi naturally associated with W. somnifera for FCRR suppression and for tomato growth promotion. Further investigations are required in regard to mechanisms of action involved in disease suppression and plant growth promotion.

Application effects of biogas slurry partly substituting for chemical fertilizer on autumn tomato production in winter-solar greenhouse

To explore the effects of biogas slurry coordinating chemical fertilizer on growth promotion of tomato, we used three kinds of typical biogas slurry as concentrated nutrient solution, respectively fermented from raw duck manure, pig manure, cow dung, while urea, monocalcium phosphate and potassium sulphate as auxiliary nutrition to balance the nutrient difference between different dilution ratios of biogas slurry. The results showed the biogas slurry partially substituting chemical fertilizer could significantly improve soil fertility, including available nitrogen, phospho-rus, and potassium. As for water soluble calcium, magnesium, iron, manganese and zinc in soil, biogas slurry application could activate their availability, with the magnitude of such effects depended on the fermentation level of raw materials and dilution ratio. Compared with chemical fertilizer, coordinating biogas liquid fertilizer significantly promoted the growth of tomato, with the yield increased by 55.9%-232.8% and the chemical fertilizer dosage decreased by 18.2%-85.0%. Furthermore, such effects became more prominent along with prolonged time. The fruit quality was significantly improved with the increases of lycopene, ascorbic acid and total sugar, and the decreases of acidity and nitrite concentration, and the decrease of NO2- by 35.6%-90.3%. In addition, the taste flavor of fruits was 7.0%-20.3% higher than that of chemical fertilizer treatment. The yield and quality of tomato took on nonlinear synchronization, and the relation between taste flavor and sugar/acid showed significantly positive correlation, which was affected by fertilizer type. Biogas slurry partly substituting chemical fertilizer could achieve the goals of high yield, high quality, environmental protection, efficient utilization of agricultural resources in tomato production.

Biocontrol of Root-Knot Nematode Meloidogyne incognita by Chitinolytic Trichoderma spp.

The inhibitory potential of chitinolytic Trichoderma spp. was assayed against Meloidogyne incognita in vitro and in vivo. Sixteen Trichoderma isolates were assayed for chitinase activity using basal solid medium supplemented with colloidal chitin. Isolates recorded high chitinolytic activity were identified morphologically as Trichoderma asperelloides, T. hamatum, T. harzianum and T. viride. The four species were quantitatively assayed for total and specific chitinase activity. T. asperelloides showed maximum chitinase activity (1.736 U/mL). In vitro studies revealed that egg hatching and second juveniles vitality of root-knot nematodes were significantly inhibited by chitinase-containing growth culture of the four selected chitinolytic Trichoderma species. However, the reduction effect was directly correlated with the concentration of fungal growth suspension. Under greenhouse conditions, three sequentially treatments of soil with homogenized culture suspension were studied. Trichoderma species significantly reduced the final nematode population by 97.81% and root galling by 92.81%. Moreover, all tested Trichoderma species obviously promoted tomato growth compared to untreated control. Significant positive correlation between the biocontrol efficacy of Trichoderma species against root-knot nematodes and their chitinolytic activity was confirmed. The most potential chitinolytic species, T. asperelloides, also recorded the highest biocontrol activity against M. incognita.

Soil Type-Dependent Interactions of P-Solubilizing Microorganisms with Organic and Inorganic Fertilizers Mediate Plant Growth Promotion in Tomato

The use of plant growth-promoting microorganisms (PGPMs) as bio-effectors (BEs) to improve the nutrient acquisition of crops has a long history. However, limited reproducibility of the expected effects still remains a major challenge for practical applications. Based on the hypothesis that the expression of PGPM effects depends on soil type and the properties of the applied fertilizers, in this study, the performance of selected microbial inoculants was investigated for two contrasting low-fertility soils supplied with different organic and inorganic fertilizers. Greenhouse experiments were conducted with tomato on an alkaline sandy loam of pH 7.8 and an acidic loamy sand of pH 5.6 with limited phosphate (P) availability. Municipal waste compost, with and without poultry manure (PM), rock phosphate (RP), stabilized ammonium, and mineral nitrogen, phosphorus and potassium (NPK) fertilization were tested as fertilizer variants. Selected strains of Bacillus amyloliquefaciens (Priest et al. 1987) Borriss et al. 2011 (FZB42) and Trichoderma harzianum Rifai (OMG16) with proven plant growth-promoting potential were used as inoculants. On both soils, P was identified as a major limiting nutrient. Microbial inoculation selectively increased the P utilization in the PM-compost variants by 116% and 56% on the alkaline and acidic soil, while RP utilization was increased by 24%. This was associated with significantly increased shoot biomass production by 37–42%. Plant growth promotion coincided with a corresponding stimulation of root growth, suggesting improved spatial acquisition of soluble soil P fractions, associated also with improved acquisition of nitrogen (N), potassium (K), magnesium (Mg), and calcium (Ca). There was no indication for mobilization of sparingly soluble Ca phosphates via rhizosphere acidification on the alkaline soil, and only mineral NPK fertilization reached a sufficient P status and maximum biomass production. However, on the moderately acidic soil, FZB42 significantly stimulated plant growth of the variants supplied with Ca–P in the form of RP + stabilized ammonium and PM compost, which was equivalent to NPK fertilization; however, the P nutritional status was sufficient only in the RP and NPK variants. The results suggest that successful application of microbial biofertilizers requires more targeted application strategies, considering the soil properties and compatible fertilizer combinations.

Molecular detection and management of tomato leaf curl virus with Pseudomonas fluorescens and chitosan

Tomato production is affected by various fungal, bacterial and viral diseases that attribute to considerable yield losses. Among all the diseases of tomato, Tomato Leaf Curl Virus (ToLCV) disease is cited to be the most devastating both in terms of quantitative and qualitative yield losses. Often, the loss reaches to the extent of 100% during summer throughout India. The virus associated with tomato leaf curl disease was detected by PCR using coat protein specific primers. The present investigations were carried out with potent Pseudomonas fluorescens isolates alone and along with elicitor molecule chitosan to determine its ability to control ToLCV in tomato. Different formulations of P. fluorescens and chitosan were evaluated for controlling ToLCV and growth promotion of tomato. It was found that the application of P. fluorescens isolates Pf1 and Pf2 @ 5kg/ha in combination with chitosan @ 5% reduces the severity of the ToLCV disease by 80 – 90 %. Application of chitosan and P. fluorescens alone caused 60 – 70% reduction in severity of ToLCV disease. Moreover, the plants inoculated with the chitosan based formulation of P. fluorescens isolates Pf1 and Pf2 recorded maximum plant height, fruit number and yield/plant over the control in potted condition. The results, thus, indicate that addition of chitosan has enhanced the biocontrol efficacy of P. fluorescens against ToLCV.

Antifungal and plant growth-promoting activities of Streptomyces roseoflavus strain NKZ-259

Biocontrol approach, using beneficial microorganisms, is becoming an important alternative to the use of chemical fungicides to control crop diseases. Therefore there is a need to found new effective biocontrol agents. Herein, a bacterial strain named NKZ-259 was isolated from soil samples obtained from Qilian Mountain, Qinghai, using the dilution plate method and streak plate technique. Strain NKZ-259 was identified as Streptomyces roseoflavus based on 16S rDNA sequencing, which displayed high antagonistic activity against six fungal pathogens tested. A greenhouse experiment showed that the use of NKZ-259 fermentation broth reduced the incidence of the tomato gray mold by 66.67%, and promoted the growth of tomato and pepper seedlings, with a significant increase in plant height, root length, and fresh weight compared to controls; the field experiment also showed the growth promotion of tomato and pepper seedlings by the use of NKZ-259 fermentation broth. Furthermore, indoleacetic acid (IAA) production was also detected in strain NKZ-259 using the Salkowski’s reagent method, and was important for its plant growth-promoting effects. The results suggest that NKZ-259 has potential for commercial application as a biofertilizer or biocontrol agent.

A Biocontrol Strain of Bacillus subtilis WXCDD105 Used to Control Tomato Botrytis cinerea and Cladosporium fulvum Cooke and Promote the Growth of Seedlings.

In this study, a strain named WXCDD105, which has strong antagonistic effects on Botrytis cinerea and Cladosporium fulvum Cooke, was screened out from the rhizosphere of healthy tomato plants. The tomato plants had inhibition diameter zones of 5.00 mm during the dual culture for four days. Based on the morphological and physiological characteristics, the 16S rDNA sequence, and the gyrB gene sequence analysis, the strain WXCDD105 was identified as Bacillus subtilis suBap. subtilis. The results of the mycelial growth test showed that the sterile filtrate of the strain WXCDD105 could significantly inhibit mycelial growth of Botrytis cinerea and Cladosporium fulvum Cooke. The inhibition rates were 95.28 and 94.44%, respectively. The potting experiment showed that the strain WXCDD105 made effective the control of tomato gray mold and tomato leaf mold. The control efficiencies were 74.70 and 72.07%. The antagonistic test results showed that the strain WXCDD105 had different degrees of inhibition on 10 kinds of plant pathogenic fungi and the average inhibition rates were more than 80%. We also found that the strain WXCDD105 stimulated both the seed germination and seedling growth of tomatoes. Using the fermentation liquid of WXCDD105 (108 cfu·mL−1) to treat the seeds, the germination rate and radicle length were increased. Under the treatment of the fermentation liquid of the strain WXCDD105 (106 cfu·mL−1), nearly all physiological indexes of tomato seedlings were significantly higher than that of the control groups. This could not only keep the nutritional quality of tomato fruits but also prevent them from rotting. This study provided us with an excellent strain for biological control of tomato gray mold, tomato leaf mold, and tomato growth promotion. This also laid the technical foundation for its application.

Stress tolerance and plant growth promotion potential of Enterobacter ludwigii PS1 isolated from Seabuckthorn rhizosphere

Abstract Plant growth promotion by microbial inoculants is affected by environmental factors. The study was therefore aimed at developing microbial inoculants for promoting tomato growth in regions experiencing temperature, pH and salt stressed conditions. Enterobacter ludwigii PS1 capable of solubilizing insoluble inorganic phosphate was isolated from Seabuckthorn rhizosphere growing in the Indian trans-Himalaya. PS1 showed ability to solubilize insoluble phosphate under different stress conditions viz. 4–44 °C temperature, 1–5% salt concentration and 4–12 pH range. The isolate exhibited multiple plant growth promoting traits viz. auxin (24.3 mg L−1), siderophore (79%) and hydrogen cyanide (0.21 O.D at 625 nm) production. Tomato seed bacterization resulted in 25% and 37% increase in shoot and root length. Inoculation of tomato seedling with PS1 promoted plant growth in pot trial experiments in trans-Himalayan (34°08′0.2″ N, 77°34′0.3″ E, 3340 m asl) condition. Increase in fruit yield was 15% in open and 27% in shade net condition. E. ludwigii PS1 with phosphate-solubilizing ability under stress conditions appears to be attractive for exploring its plant growth-promoting activities towards development of microbial inoculants in stressed regions.

English

Fusarium crown and root rot (FCRR) is a serious tomato disease in Tunisia which is difficult to control due to its soilborne nature and to the luck of genetic resistance. In the current study, native Solanum linnaeanum was explored as potential source of effective fungal agents for disease biocontrol. Eight fungal isolates, recovered from S. linnaeanum plants growing in the Tunisian Centre-East and shown able to colonize roots, crowns and stems of tomato (Solanum lycopersicum L.) seedlings, were tested for their ability to inhibit Fusarium oxysporum f. sp. radicis-lycopersici (FORL), the causal agent of this disease, and to promote plant growth. Tomato seedlings inoculated or not with FORL and treated using tested fungal isolates, exhibited significant increments in their growth parameters. Tested as conidial suspensions or cell-free culture filtrates, I74 and I92 isolates were the most active leading to 92.8% decrease in FCRR severity and 89.3 to 95.2% lowered vascular browning extent as compared to FORL-inoculated and untreated controls. These two isolates were microscopically and macroscopically described and identified using rDNA sequencing gene as being Penicillium crustosum I74 (MF188258) and Fusarium proliferatum I92 (MF188256). Pathogen mycelial growth was inhibited by 29.4 to 78.1% using their conidial suspensions and by 67.5 to 82% with their cell-free culture filtrates. P. crustosum I74 and F. proliferatum I92 showed chitinolytic, proteolytic and amylase activities. Only I92 isolate exhibited a lipolytic activity. Our study clearly demonstrated that I74 and I92 isolates were promising candidates for suppressing FCRR severity and promoting tomato growth. Further investigations are required for elucidating their mechanisms of action involved in disease suppression and plant growth promotion. Key words: Antifungal activity, associated fungi, Fusarium oxysporum f. sp. radicis-lycopersici, Solanum linnaeanum, tomato growth.

Trichoderma spp. isolates with potential of phosphate solubilization and growth promotion in cherry tomato1

ABSTRACT Trichoderma fungi are considered relevant plant growth promoters for increasing the efficiency in the use of nutrients, as well as acting as biological control agents. This study aimed to select Trichoderma spp. isolates with potential for phosphate solubilization and their application as growth promoters in interaction with homeophatic preparations, in cherry tomato. Among 16 Trichoderma spp. isolates obtained from soils of organic tomato growing areas tested in vitro, together with a commercial product (Trichodermil®), two of them showed the ability for indole-3-acetic acid production and phosphate solubilization. The Trichoderma “R” had the highest mycelial growth speed index and presented twice as much spores than the commercial product. An in vivo experiment was also conducted in a greenhouse, in order to observe the potential of Trichoderma spp. isolates and homeophatic preparations on the cherry tomato growth promotion, using a randomized block experimental design, in a 4 x 3 factorial arrangement, with three Trichoderma isolates and two homeopathic preparations (Phosphorus 6CH and Carbo vegetabilis 6CH) + treatment without homeopathic preparation. The leaf area and dry mass of leaves and roots were determined. It was possible to observe that the isolate “R”, identified as Trichoderma asperellum, was effective in the cherry tomato growth promotion, while the homeopathic preparations applied did not show any effect.

Role of Bacillus amyloliquefaciens Y1 in the control of Fusarium wilt disease and growth promotion of tomato

ABSTRACTThe objective of this study was to examine the effects of Bacillus amyloliquefaciens Y1 on the control of Fusarium wilt disease and subsequent improvement in the growth of tomato plants. The Y1 strain strongly inhibited Fusarium oxysporum f. sp. lycopersici in vitro and also produced indole-3-acetic acid (IAA) in both the presence and absence of tryptophan. Over 96% of tomato seeds germinated when treated with either water, tryptone soy broth, or Y1 cultures, whereas root (5.40 cm) and shoot (5.15 cm) lengths were greatest in tomato seedlings treated with Y1 cultures that lacked tryptophan. Three experimental treatments – Black White medium (BW), BW medium with a commercial fungicide (BW + F), and Y1 culture inoculated in BW medium (Y1) – were applied to control Fusarium wilt disease under in vivo conditions. Application of Y1 culture and BW + F led to significantly lower disease incidence than did BW; moreover, shoot length and fresh and dry weight of both roots and shoots were greater in plants treated with Y1 than in plants treated with either BW or BW + F. A similar trend was observed for chitinase and β-1,3-glucanase activities in roots and leaves of tomato plants in all treatment groups over most of the experimental period. Finally, the presence of Y1 in the rhizospheric soils of Y1-treated plants resulted in a significant reduction in the populations of other bacteria. The results of our study demonstrated the effectiveness of Y1 not only in the control of Fusarium wilt disease but also for the enhancement of plant growth in cultivated tomato.

Development of a new type of biological organic fertilizer and its effect on the growth promotion of tomato

The objective of this study was to improve the ability of sporulation production of Trichoderma guizhouense NJAU4742 under solid state fermentation by using rice straw and amino acids as resources, and the fermentation products were used as inoculants of the organic fertilizers adding with different ratios of amino acids solution to develop a new type of biological organic fertilizer. The results indicated that the optimal condition for sporulation by T. guizhouense NJAU4742 was soaking in 30 times diluted amino acid solution for one whole night, with initial pH 3.5, 75% of moisture content and 30% of corn powder, under which the sporulation reached to 2.40×1010 CFU·g-1. The fermentation products were inoculated at 2% into the mature organic fertilizer containing 20% of amino acids solution, and the sporulation and IAA content were 6.40×109 CFU·g-1 and 38.66 mg·kg-1, which were 1142.30 and 1.42 times higher than that of CK after 7 days, respectively. Pot experiment showed that biological organic fertilizer could significantly promote the growth of tomato, and the height of the tomato increased by 98.8% and 23.8%, respectively, compared with CK. The stem diameters of AT (amino acids + mature organic fertilizer + T. guizhouense NJAU4742) and AA (amino acids + mature organic fertilizer) were increased by 58.9% and 10.3%, respectively, compared with CK. As for the chlorophyll, leaf length and leaf width, the values also increased significantly. The highest spore content was obtained by using amino acids and rice straw as substrates under solid state fermentation (SSF), which overcame the difficulties of producing new type of biological organic fertilizer during the large scale industrial production. Biological organic fertilizer and amino acids organic fertilizer could significantly promote the growth of tomato compared with the chemical fertilizer, and had a good application prospect in intensive agriculture.

Suppressing Fusarium Crown and Root Rot infections and enhancing the growth of tomato plants by Lycium arabicum Schweinf. Ex Boiss. extracts

Leaf, stem and fruit extracts of a wild medicinal plant, Lycium arabicum, were assessed for their ability to promote tomato growth and to suppress Fusarium Crown and Root Rot (FCRR), a damaging tomato soilborne disease in Tunisia, caused by Fusarium oxysporum f. sp. radicis-lycopersici (FORL). Aqueous and organic extracts (at 1, 2, 3 and 4% (v/v)) were screened in vitro for their antifungal activity. Disease severity was decreased significantly 60days after inoculation. Leaf (LC2) and fruit (FC2) aqueous extracts used at 30% (w/v) were the most effective in inducing 84.6 and 61.5% reduction of leaf damage severity and 84.9 and 82.9% decrease in the vascular browning extent, respectively, as compared to FORL-inoculated and untreated control. A significant improvement in growth of treated and FORL-inoculated tomato plants cv. Rio Grande was found. LC2-based treatment was the most effective in increasing growth by 65–70% relative to control. Moreover, tested on FORL-free plants, all L. arabicum aqueous extracts had significantly enhanced growth compared to the control. Root length and aerial part height were improved by 46–60%, root and aerial part fresh weight were enhanced by 23–60.8% and 22.2–64.9%, respectively, and tomato stem diameter was increased by 19.1%. In vitro, the extracts antifungal activity, screened using the poisoned food technique, varied significantly depending on plant organs, concentrations tested and organic solvent used for extraction. All aqueous extracts inhibited FORL radial growth where percentage inhibition reached 33.5, 24.4 and 30.3%, as compared to control, by leaf, stem and fruit extracts at 4%, respectively. Butanolic leaf extract at 4%, was the most active, inducing 41.4% reduction in FORL mycelial growth. L. arabicum leaf aqueous extract was the most efficient for disease severity suppression and tomato growth promotion. Thus, this wild plant could be explored as a potential source of antifungal and biofertilizing compounds.

A novel split-pot bioassay to screen indole acetic acid producing rhizobacteria for the improvement of plant growth in tomato [Solanum lycopersicum L.

In the present study, we developed a split-pot bioassay to screen the indole acetic acid producing rhizobacteria to improve the adventitious root initiation and plant growth promotion in tomato. Based on the ability to produce IAA, 12 isolates were selected among which IRB1 and IRB2 were negative and other rhizobacteria showed a varied level of IAA production (0–84.7μg/ml) when grown in media supplemented with increasing concentration of L-tryptophan (0–500μg/ml). Results of split-pot bioassay revealed the capability of IAA producing bacteria to stimulate the growth of adventitious roots on tomato stem which was significantly (P≤0.05) higher than control and IAA negative bacterial treatments. Further enhanced growth of adventitious roots was in accordance with their IAA producing ability. The probability of obtaining consistent results with split-pot bioassay was analyzed by repeating the experiments ten times and subjecting the data to statistical analysis. The results obtained indicated that split-pot bioassay has significantly lesser variations between the individual experiments in comparison with regular bioassay. Further, randomly selected 31 rhizobacteria with unknown identity and characters from the rhizosphere of tomato plants were screened by employing the split-pot bioassay. Isolates UKR8, UKR19, UKR23 and UKR30 were found significant (P≤0.05) in increasing the number and length of adventitious roots and increase in root length, shoot length and fresh weight under greenhouse conditions when compared to regular bioassay. It was also recorded that these bacteria were found to produce IAA to various extent. A possible application of split-pot bioassay in screening IAA producing rhizobacteria and their further application in improving tomato plant growth is discussed in the present study.

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

ABSTRACTRhizoctonia 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.

Indole Acetic Acid Production and Growth-Promoting Activity of Methylobacterium extorquens MP1 and Methylobacterium zatmanii MS4 in Tomato

ABSTRACTPink-pigmented facultative methylotrophs (PPFMs) are prevalent aerobic bacteria colonizing the phyllosphere of various plant species. PPFMs have the ability to utilize plant-derived methanol as an energy substrate when plants are being colonized under stress. The study was undertaken to explore the metabolic potential of methylotrophs isolated from diverse sources and their role in growth and development of Tomato (Solanum lycopersicum L.) plants, because it is easily grown under laboratory conditions. PPFMs were isolated from the phyllosphere of Peach (Prunus persica L.) and Strawberry (Fragaria ananassa L.) by the leaf imprint method. The bacterial isolates MP1 and MS4 are rod shaped as confirmed by scanning electron microscopy (SEM) analysis. Methylotrophy of the isolates was authenticated by polymerase chain reaction (PCR) amplification of the highly conserved mxaF gene. The 16S rRNA gene sequences demonstrated that the isolates MP1 and MS4 were Methylobacterium extorquens and Methylobacterium zatmanii, respectively. High-performance thin-layer chromatographic analysis indicated production of indole acetic acid (IAA) by M. extorquens MP1 and M. zatmanii MS4. The amount of IAA produced was 10.353 and 8.473 μg·mL−1 for M. extorquens MP1 and M. zatmanii MS4, respectively. Tomato seed were treated with M. extorquens and M. zatmanii and had seed vigor indices (SVIs) of 1383.33 ± 90.26 and 1240.79 ± 244.09, respectively, compared to untreated control seed, which had an SVI of 1031.68 ± 83.96. Foliar application of M. extorquens MP1 and M. zatmanii MS4 augmented its impact on plant growth promotion in tomato compared to the control. The increased production of IAA and subsequent enhancement in growth-promoting traits indicates that methylotrophs from diverse plant species can be used to improve early plant development in tomato under controlled conditions.

Plant Growth Promoting Activity of Pink Pigmented Facultative Methylotroph - Methylobacterium extorquens MM2 on Lycopersicon esculentum L.

Pink pigmented facultative methylotrophs (PPFMs) are diversified group of microorganisms that promote plant growth by producing indole acetic acid (IAA) and cytokinins. The objective of the present study is to isolate and characterize methylotrophic bacteria from the phyllosphere of mustard plant (Brassica niagra) and to study their plant growth promotion in tomato (Lycopersicon esculentum L.). Bacteria were isolated from the phyllosphere and the conserved mxaF gene sequence was amplified. Production of IAA was determined by High Performance Thin Layer Chromatography (HPTLC) and further quantified by spectrophotometric analysis. Effect of seed bacterization with the bacterial isolate MM2 was studied for percentage seed germination, root & shoot length. Based on NCBI BLAST search of the mxaF sequence obtained, the bacterial isolate was identified as Methylobacterium extorquens MM2. The amount of IAA produced by M. extorquens MM2 was 6.16 μg/ml. M. extorquens MM2 significantly increased seed vigour index (SVI) in tomato plants. The SVI of the treated plant was 1462.56 ± 83.96 as compared to the control, 1019.94 ± 113.61. Foliar application of M. extorquens MM2 also contributed a substantial impact on growth of tomato plant. The bacterial isolate M. extorquens MM2 thus can be employed in the crops for sustainable agriculture.