Charcoal Rot Disease Research Articles

Associations between charcoal rot disease and grain yield in different sowing dates in spring maize (Zea mays L.)

Associations between charcoal rot disease and grain yield in different sowing dates in spring maize (Zea mays L.)

Secretome Analysis of Macrophomina phaseolina Identifies an Array of Putative Virulence Factors Responsible for Charcoal Rot Disease in Plants.

Macrophomina phaseolina is a global devastating necrotrophic fungal pathogen. It causes charcoal rot disease in more than 500 host plants including major food crops, pulse crops, fiber crops, and oil crops. Despite having the whole-genome sequence of M. phaseolina, understanding the M. phaseolina genome-based plant–pathogen interactions is limited in the absence of direct experimental proof of secretion. Thus, it is essential to understand the host–microbe interaction and the disease pathogenesis, which can ensure global agricultural crop production and security. An in silico–predicted secretome of M. phaseolina is unable to represent the actual secretome. We could identify 117 proteins present in the secretome of M. phaseolina using liquid chromatography–electrospray ionization–tandem mass spectrometry. Data are available via ProteomeXchange with identifier PXD032749. An array of putative virulence factors of M. phaseolina were identified in the present study using solid-state culture. Similar virulence factors have been reported in other plant pathogenic fungi also. Among the secretory fungal proteins with positive economic impacts, lignocellulolytic enzymes are of prime importance. Further, we validated our results by detecting the cell wall–degrading enzymes xylanase, endoglucanase, and amylase in the secretome of M. phaseolina. The present study may provide a better understanding about the necrotrophic fungi M. phaseolina, which modulate the host plant defense barriers using secretory proteins.

Histopathological changes in root and stem of mungbean exposed to Macrophomina phaseolina and dry biomass of Chenopodium quinoa.

Mungbean production is affected by a fungal pathogen Macrophomina phaseolina. A pot experiment was carried out to check the effect of quinoa (Chenopodium quinoa Willd.) dry biomass on the histopathological features of mungbean exposed to M. phaseolina. For this, 1%, 2% and 3% (wt/wt) of C. quinoa dry biomass was mixed in the soil inoculated with M. phaseolina. The highest disease incidence (36%) was recorded in the positive control (only M. phaseolina). Different treatments of quinoa dry mass reduced disease incidence to 4-7%. After 4 weeks of germination, stem and root sections were stained in phloroglucinol-HCl, ferric chloride and Lugol's iodine stains for the detection of lignin, polyphenols and starch granules, respectively, and studied under light microscope. Plants of positive control showed damaged cells, and heavy deposition of lignin, phenolics and starch granules as compared to plants of the negative control and those grown in the soil amended with different doses of dry biomass of quinoa. For better understanding, plant root and stem sections were studied under a scanning electron microscope. Plant sections from positive control exhibited the presence of M. phaseolina sclerotial bodies and hyphal growth, whereas in negative control normal cell structures were observed. However, C. quinoa amended stem and root sections revealed the presence of high gel deposition with normal cell structures and no pathogen establishment. This study concludes that application of C. quinoa is an effective and natural remedy to activate the resistance mechanism in plants and to combat the adverse effects of M. phaseolina. HIGHLIGHTS: Macrophomina phaseolina causes charcoal rot in mungbean. Chenopodium quinoa amendment significantly reduced incidence of charcoal rot disease. M. phaeolina increased concentrations of polyphenols, lignin and starch granules in mungbean.

Pigment Produced by Glycine-Stimulated Macrophomina Phaseolina Is a (−)-Botryodiplodin Reaction Product and the Basis for an In-Culture Assay for (−)-Botryodiplodin Production

An isolate of Macrophomina phaseolina from muskmelons (Cucumis melo) was reported by Dunlap and Bruton to produce red pigment(s) in melons and in culture in the presence of added glycine, alanine, leucine, or asparagine in the medium, but not with some other amino acids and nitrogen-containing compounds. We explored the generality and mechanism of this pigment production response using pathogenic M. phaseolina isolates from soybean plants expressing symptoms of charcoal rot disease. A survey of 42 M. phaseolina isolates growing on Czapek-Dox agar medium supplemented with glycine confirmed pigment production by 71% of isolates at the optimal glycine concentration (10 g/L). Studies in this laboratory have demonstrated that some pathogenic isolates of M. phaseolina produce the mycotoxin (−)-botryodiplodin, which has been reported to react with amino acids, proteins, and other amines to produce red pigments. Time course studies showed a significant positive correlation between pigment and (−)-botryodiplodin production by selected M. phaseolina isolates with maximum production at seven to eight days. Pigments produced in agar culture medium supplemented with glycine, beta-alanine, or other amines exhibited similar UV-vis adsorption spectra as did pigments produced by (±)-botryodiplodin reacting in the same agar medium. In a separate study of 39 M. phaseolina isolates, red pigment production (OD520) on 10 g/L glycine-supplemented Czapek-Dox agar medium correlated significantly with (−)-botryodiplodin production (LC/MS analysis of culture filtrates) in parallel cultures on un-supplemented medium. These results support pigment production on glycine-supplemented agar medium as a simple and inexpensive in-culture method for detecting (−)-botryodiplodin production by M. phaseolina isolates.

Pathogenic Interactions between Macrophomina phaseolina and Magnaporthiopsis maydis in Mutually Infected Cotton Sprouts

The soil fungus Macrophomina phaseolina, the charcoal rot disease agent, poses a major threat to cotton fields. In Israel, highly infected areas are also inhabited by the maize pathogen Magnaporthiopsis maydis. This study reveals the relationships between the two pathogens and their impact on cotton sprouts. Infecting the soil 14 days before sowing (DBS) with each pathogen or with M. phaseolina before M. maydis caused a strong inhibition (up to 50–65%) of the sprouts’ development and survival, accompanied by each pathogen’s high DNA levels in the plants. However, combined or sequence infection with M. maydis first led to two distinct scenarios. This pathogen acted as a beneficial protective endophyte in one experiment, leading to significantly high emergence and growth indices of the plants and a ca. 10-fold reduction in M. phaseolina DNA in the sprouts’ roots. In contrast, M. maydis showed strong virulence potential (with 43–69% growth and survival suppression) in the other experiment, proving its true nature as an opportunist. Interestingly, soil inoculation with M. phaseolina first, 14 DBS (but not at sowing), shielded the plants from M. maydis’ devastating impact. The results suggest that the two pathogens restrict each other, and this equilibrium may lead to a moderate disease burst.

Control of Fungal Diseases and Fruit Yield Improvement of Strawberry Using Bacillus velezensis CE 100.

Due to the increasing health and environmental risks associated with the use of fungicides in agriculture, alternatives—such as using plant growth-promoting bacteria (PGPB) to suppress phytopathogens—that simultaneously improve plant yield, are important. This study evaluated the biocontrol efficiency of Bacillus velezensis CE100 against Macrophomina phaseolina and Fusarium oxysporum f. sp. fragariae, the respective causal agents for charcoal rot and fusarium wilt diseases in strawberry, and its potential to enhance strawberry growth and fruit production. B. velezensis CE 100 produced fungal cell wall-degrading enzymes, chitinases, and β-1,3-glucanases; and inhibited the mycelial growth of M. phaseolina and F. oxysporum f. sp. fragariae by 64.7% and 55.2%, respectively. The mycelia of both phytopathogenic fungi showed severe swelling and rupturing of the hyphae compared to the smooth, normal growth in the control group. Moreover, B. velezensis CE100 produced up to 2.8 units/mL of indole-3-acetic acid (IAA) during incubation and enhanced root biomass in strawberries. Consequently, B. velezensis CE 100 not only increased the fruit yield of strawberries by controlling the fungal diseases but also through enhancing plant growth. The findings of this study indicate that B. velezensis CE100 could be a safe, ecofriendly biocontrol alternative to chemical fungicides in strawberry production.

Determination of the Antagonistic Effects of Some Rhizospheric Bacteria against Macrophomina phaseolina under In Vitro Conditions

Macrophomina phaseolina (Tassi) Goid. is a fungal pathogen causes charcoal rot disease (Sin: Rhizoctonia bataticola) and is responsible for significant yield losses in many plants. In our study, we aimed to evaluate the antagonistic ability of 39 different bacteria, isolated from the fields of sugar beet in 2019, against the pathogen Macrophomina phaseolina isolated from sugar beet, beans and chickpeas. Approximately 31% of the bacteria showed antibiosis effect against the pathogen. It was determined that the effectiveness level of Lelliottia amnigena, Bacillus atrophaeus, B.pumilus and B. cereus (7 isolates) was moderate to high against Macrophomina phaseolina. Bacillus atrophaeus (PTo15-1a) showed the highest efficacy of 80%, 72.94% and 82.35% against Macrophomina phaseolina of chickpea, bean and sugar beet respectively. Lelliottia amnigena (Pto 14-1b) was moderately effective (57.78%) against the chickpea isolate of the pathogen. It was observed that of the seven Bacillus cereus isolates used in the experiment, three isolates (Pto14-1a, Pto12-1b, Pto17-1b) were highly effective against the chickpea pathogen, two (Pto12-1b, Pto14-2b) against bean pathogen, and one (Pto15-1b) against sugar beet isolate. Results have shown varied level of antagonism by different test bacterial against different Macrophomina phaseolina isolates, while the highest level of antibiosis shown by Bacillus atrophaeus against all pathogenic isolates indicated that it can be a potential future bioagent in managing the disease.

Occurrence of Macrophomina phaseolina in Israel: Challenges for Disease Management and Crop Germplasm Enhancement.

Macrophomina phaseolina is a soil-borne fungal pathogen infecting many important crop plants. The fungus, which can survive on crop debris for a long period of time, causes charcoal rot disease by secreting a diverse array of cell-wall degrading enzymes and toxins. M. phaseolina thrives during periods of high temperatures and arid conditions, as typically occur in Israel and other countries with a Mediterranean climate. Crop losses due to charcoal rot can be expected to increase and spread to other countries in a warming global climate. Management of this pathogen is challenging, requiring an array of approaches for the various crop hosts. Approaches that have had some success in Israel include grafting of melons and watermelons on resistant squash rootstocks and soil application of fungicide to reduce disease incidence in melons, fumigation and alterations in planting date and mulching of strawberries, and alteration in irrigation regime of cotton. Elsewhere, these approaches, as well as soil amendments and addition of organisms that are antagonistic to M. phaseolina, have had success in some crop situations. Management through host resistance would be the most sustainable approach, but it requires identifying a resistant germplasm for each crop and introgressing the resistance into the leading cultivars. Resistance to charcoal rot is under complex genetic control in most crops, posing a great challenge for its introgression into elite germplasm. Moreover, fast, reliable methods of screening for resistance would have to be developed for each crop. The toothpick-inoculation method used by us holds great promise for selecting resistant germplasm for melons and possibly for sesame, but other methodologies have to be devised for each individual crop.

Secretome analysis identified extracellular superoxide dismutase and catalase of Macrophomina phaseolina.

Macrophomina phaseolina, a necrotrophic fungal pathogen is known to cause charcoal rot disease in food crops, pulse crops, oil crops and cotton and fibre crops. Necrotrophic fungi survive on dead plant tissue. It is well known that reactive oxygen species (ROS) are produced by the host plant during plant-pathogen interaction. However, it is still unclear how M. phaseolina can overcome the ROS-induced cellular damage. To mimic the invasion of M. phaseolina inside the plant cell wall, we developed solid substrate fermentation where M. phaseolina spore suspension was inoculated on a wheat bran bed and incubated for vegetative growth. To analyse the secretome of M. phaseolina after different day interval, its secretory material was collected and concentrated. Both superoxide dismutase (SOD) and catalase were detected in the secretome by zymogram. The presence of SOD and catalase was further confirmed by liquid chromatography based mass spectrometry. The physicochemical properties of M. phaseolina catalase in terms of stability towards pH, temperature, metal ions and chaotropic agent and inhibitors indicated its fitness at different environmental conditions. Apart from the production of catalase in SSF, the studies on this particular microorganism may also have significance in necrotrophic fungal pathogen and their susceptible host plant interaction.

Biocontrol of Macrophomina phaseolina (Tassi) Goid causing charcoal rot disease in Lycopersicon esculentum L. by using multi species bacterial consortia

Plant growth-promoting bacterial strains (LEP1-LEP31) were isolated from rhizosphere of Lycopersicon esculentum L. (Tomato) and screened for their plant growth promoting (PGP) activities. On the basis of morphological, physiological, biochemical, carbon source utilization and molecular characterization, these strains were identified as Pseudomonas sp., Azotobacter sp. and Bacillus sp. For antagonistic activities all the strains were subject to the chitinase activities by the development of clear halo around the inoculated bacterial spots when loaded on chitin (0.2%) supplemented mediumBased on pot and field trial results of individual strains and consortium application, it may be concluded that all the three strains i.e. Pseudomonas sp. LEP17, Azotobacter sp. strain LEP21 and Bacillus sp. strain LEP25 showed plant growth promoting effects. The growth promotion provided by these strains was apparently related to improve shoot and root development, which resulted in better nutrient uptake capability and suppression of plant pathogen. All these three strains were superior in this regard because they provided the best and most consistent effects on growth and yield of L. esculentum. All these strains Pseudomonas sp. LEP17, Azotobacter sp. strain LEP21, Bacillus sp. strain LEP25 and their consortium seems to be suitable for use as a plant growth promoting and improvement of growth and yield

Complete Genome Sequence Resource for the Endophytic Burkholderia sp. Strain MS389 Isolated from a Healthy Soybean Growing Adjacent to Charcoal Rot Disease Patch.

Burkholderia sp. strain MS389, an endophytic bacterium, was isolated from a healthy soybean plant growing adjacent to a patch of plants affected by charcoal rot disease, caused by the fungal pathogen Macrophomina phaseolina. Preliminary studies demonstrated that strain MS389 possesses antimicrobial activities against multiple plant pathogens. Burkholderia sp. strain MS389 was found to have three circular chromosomes of 3,563,380 bp, 3,002,449 bp, and 1,180,421 bp in size, respectively. The 7,746,250-bp genome, with 66.73% G+C content, harbors 6,756 protein coding genes in the predicted 6,985 genes. In total, 18 rRNAs, 68 tRNAs, and four ncRNAs were identified and 139 pseudogenes were annotated as well. The findings of this study will provide valuable data to explore the antimicrobial mechanisms of the endophytic bacterial strain.

Isolation and Identification of Some Biocontrol Fungi and Evaluation of Their Efficacy Against Charchol Rot Disease Caused by Macrophomina phaseolina on Mung Bean

This study aimed to isolate and identify Macrophomina phaseolina fungus which was the causal aget of Charcol rot disease on mung bean (Vigna radita Wilczek L) from Elgadisia Governorate in order to isolate, diagnose, and evaluate efficacy of biological control fungal agents isolalated from the rhizosphere of the host plant. The biocontrol agents T. koningii, C. globosum and A. carbonarius were effective in inhibiting the pathogenic fungus under laboratory and greenhouse conditions. Two isolates of M. phaseolina fungal pathogen were identified in most samples of infected mung bean. Pathogenicity tests showed the ability of M. phaseolina to attack the seeds and cause seed rot. Isolates 1 and 2 of the fungal pathogen reduced the seed germination rate to 71.56 and 63.75%, respectively, compared with 86.66% for the control. The results obtained indicated the presence of a significant difference between the two isolates in inducing seedlings damping-off which reached 40% and 30%, respectively, compared with 0% for the control. The disease severity of isolate 1 reached 75.3% and that of isolate 2 reached 63.6%. The inhibitory effect of the fungal antagonists T. koningii and C. globosum varied. A. carbonarius demonstrated level 3 of inhibition to the pathogenic fungus M. phaseolina, whereas C. globosum and T. koningii demostrated inhibitory levels of 2 and 1, respectively. Results obtained also indicated that treatments with antagonistic fungi T. koningii, C. globosum and A. carbonarius increased the growth parameters of the mung bean plant. The antagonistic fungus C. globosum increased the plant height, root fresh and dry weight and chlorophyll content compared with the control. Furthermore, the results showed that treatment with T. koningii increased the mung bean seed germination rate to 100% and decreased disease severity of mung bean charcoal rot disease to 45.88% as compared to 89.86% severity for the contol. Likewise, the other antagonistic fungi A. carbonarius and C. globosum also increased the mung bean seed germination , and decreased mung bean charcoal rot disease severity. Keywords : Charcoal rot disease, mung bean, Macrophomina phaseolina, T. koningii, C. globosum, A. carbonarius.

Sulfur Application Combined with Planomicrobium sp. Strain MSSA-10 and Farmyard Manure Biochar Helps in the Management of Charcoal Rot Disease in Sunflower (Helianthus annuus L.)

Sunflower (Helianthus annuus L.), a member of the Asteraceae, is one of the major oilseed crops around the world. Charcoal rot caused by Macrophomina phaseolina (Tassi) Goid is the most damaging disease of sunflowers globally. Fungicides are mostly used to control charcoal rot; however, these cause environmental pollution and pose adverse effects on the ecosystem. Therefore, ecofriendly management options are inevitable for the management of charcoal rot disease. Plant mineral nutrition, the use of plant growth-promoting rhizobacteria and biochar have recently been manipulated for the management of different plant diseases. However, the interactive effects of all these treatments have rarely been tested on charcoal rot suppression in sunflowers. This study assessed the influence of sulfur (0 and 2.25 mg/kg) combined with farmyard manure biochar (2%), NPK (20:20:20 mg/kg) and three different plant growth-promoting rhizobacteria (PGPR) strains on the charcoal rot suppression growth, yield, biochemistry and physiology of sunflower. The PGPR strains included in the study were Bacillus sp. strain MR-1/2 (regarded as PGPR1), Achromobacter sp. strain FB-14 (regarded as PGPR2) and Planomicrobium sp. strain MSSA-10 (regarded as PGPR3). The charcoal rot infestation was induced by inoculating the soil with M. phaseolina, and the impacts of the different treatments were studied on the disease infestation, growth, yield, biochemistry and physiology of sunflowers under 0 and 2.25-mg/kg S application. The results revealed that farmyard manure biochar and Planomicrobium sp. strain MSSA-10 in combination with 2.25-mg/kg S proved effective for the management of charcoal rot disease through regulating the antioxidant enzymes’ activities and strengthening the immune system of sunflower plants. The studied health markers (total chlorophyll content and carotenoids) and stress markers (total protein content, catalase and peroxidase) were significantly altered by the applied treatments under 0 and 2.25-mg/kg S applications. The findings of the experiment indicated that both farmyard manure biochar and Planomicrobium sp. strain MSSA-10, combined with 2.25-mg/kg S, could be used to enhance the crop yield and manage charcoal rot disease in sunflowers. Farmyard manure biochar and Planomicrobium sp. strain MSSA-10 are an easy-to-apply, cost-effective, ecofriendly and sustainable option for the management of charcoal rot disease in sunflowers.

Impact of technical trainings on socio-economic status and knowledge to farmers for the management YMV and charcoal rot diseases of soybean by antagonistic microorganism and chemical pesticides

On the basis of Socio Economic Status of farmers records, technical trainings to Farmers and knowing the constraints of farmers faced during last years, an experiment was conducted in the year 2017 and 2018 Kharif season with four soybean verieties namely JS 20-29, JS 97-52, RVS 2001-4 and JS20-69 in four replications with control plot. Personal contact with farmers indicated that majority of farmers (60%)came under small land holders categories having only 3.0 ha cultivated area whereas 13.33% farmer occupied > 10ha cultivated areas considered large land holding farmers. More than 57% young farmers having age below 35 years seriously engaged in agricultural work than old age (>50years) whose interest was 26.66% followed by middle age groups ( 35-50years). As for as educational level was concerned, 56% respondents were of medium category having education between 10 th to higher secondary. Nearly 29% respondents had high qualification (Graduate and above) level while14% were of low educational level. Majority of respondents (78%) was engaged in Agricultural enterprise followed by horticulture+ (14.64%) and dairy (6.66%). Incidence of both diseases was also varied from variety to variety of soybean. Highest incidence of yellow mosaic disease was found in RVS2001-4(8.79%) followed by JS20-29 (5.57%) and JS97-52 (2.32%) whereas no incidence was observed in JS 20-69. It was observed that YMV affected plant either unable to bear the flowers and fruits (pods) or very few pods appear but dried prematurely. Results revealed that RVS2001-4 affected maximum (14.15%) with charcoal rot infection than JS20- 29 in comparison to JS97-52 whereas minimum incidence was recorded in JS20-69. Control plot affected more severely than demonstration and it was due to none application of trichoderma in seed and soil treatment. Among the soybean entries JS 2069 gave more yield (17.39q/ha ) followed by RVS2001-4 (14.57q/ha) in compassion to JS20-29 and JS97-52).Timely application of bioagent and chemical pesticides for seed/soil treatment plus spray and change of knowledge through technical training to the farmers during crop period play an important role in managed the diseases and enhanced the soybean productivity. The ratio of yield increased was 15.73% to32.04% over control. A training was organized after harvested of the crop to know the major constraints and observed that 94.66 per cent respondents were face difficulties recording lack of knowledge for identification of beneficial and damager pests followed by unavailability of quality bio-pesticides (93.33%) such as trichoderma, NPV, Bavaria basiyana and bio-fertilizers (81.33%) at local level for pests and diseases management. Besides above problems, unavailability of trained labours (78.66%), quality seed (68% ), rate of wages and problems of storage were also the important and time needed constraints.

Pathogenic Variation and Molecular Characterization of Macrophomina phaseolina, the Cause of Sesame Charcoal Rot

Macrophomina phaseolina (Tassi) Goid is one of the most important soil-borne fungi that affects sesame and causes charcoal rot disease, with a great economic challenge to sesame growers worldwide. Pathogenic and molecular characterizations of eleven M. phaseolina isolates collected from different geographical regions in Egypt were carried out to determine the pathogenicity and genetic diversity. Pathogenicity tests showed a pathogenic variability among the isolates. The identification of M. phaseolina isolates was confirmed by a specific primer and analyzed for genetic diversity using random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) markers. The correlation between RAPD analysis of M. phaseolina isolates and their pathogenicity were estimated. Cluster analysis placed the isolates in two distinct clusters and exhibited clear correlation with their pathogenicity. Analysis of ISSR profiles revealed distinct genetic diversity among isolates and showed different clusters according to the geographical regions, in which close geographic origins tend to group nearly. The present study clearly demonstrated that M. phaseolina isolates which were obtained from different geographical regions were highly variable. RAPD and ISSR markers were suitable to reflect the genetic diversity among the studied isolates and could help in DNA finger printing which can be used in future breeding programs of sesame.

Sources of Resistance to Common Bacterial Blight and Charcoal Rot Disease for the Production of Mesoamerican Common Beans in the Southern United States.

The gene pool of Mesoamerican common beans (Phaseolus vulgaris L.) includes genotypes in the small-to-medium-size seeded dry beans, as well as some snap beans from hotter environments adapted to the Southeastern United States. However, the warm and humid climate of the Southeastern United States is conducive to diseases such as Common Bacterial Blight (CBB) and Charcoal Rot (CR). The pathogens for these two diseases can survive long periods in infested soil or on seeds and are difficult to control through pesticides. Hence, field-level resistance would be the best management strategy for these diseases. The goals of this study were (1) to evaluate field-level resistance from the various commercial classes and subgroups represented in the Mesoamerican gene pool as sources for breeding beans for the region and (2) to evaluate genome-wide marker × trait associations (GWAS) using genetic markers for the genotypes. A total of 300 genotypes from the Mesoamerican Diversity Panel (MDP) were evaluated for CBB and CR in field experiments for three years. CBB resistance was also tested with a field isolate in controlled greenhouse conditions. The analysis of variance revealed the presence of variability in the MDP for the evaluated traits. We also identified adapted common bean genotypes that could be used directly in Southeastern production or that could be good parents in breeding programs for CBB and CR resistance. The GWAS detected 14 significant Single-Nucleotide Polymorphism (SNP) markers associated with CBB resistance distributed on five chromosomes, namely Pv02, Pv04, Pv08, Pv10, and Pv11, but no loci for resistance to CR. A total of 89 candidate genes were identified in close vicinity (±100 kb) to the significant CBB markers, some of which could be directly or indirectly involved in plant defense to diseases. These results provide a basis to further understand the complex inheritance of CBB resistance in Mesoamerican common beans and show that this biotic stress is unrelated to CR resistance, which was evident during a drought period. Genotypes with good yield potential for the Southeastern U.S. growing conditions were found with resistant to infection by the two diseases, as well as adaptation to the hot and humid conditions punctuated by droughts found in this region.

Biosurfactant based formulation of Pseudomonas guariconensis LE3 with multifarious plant growth promoting traits controls charcoal rot disease in Helianthus annus.

Biosurfactants are environment compatible surface-active biomolecules with multifunctional properties which can be utilized in various industries. In this study a biosurfactant producing novel plant growth promoting isolate Pseudomonas guariconensis LE3 from the rhizosphere of Lycopersicon esculentum is presented as biostimulant and biocontrol agent. Biosurfactant extracted from culture was characterized to be mixture of various mono- and di-rhamnolipids with antagonistic activity against Macrophomina phaseolina, causal agent of charcoal rot in diverse crops. Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H NMR) analysis confirmed the rhamnolipid nature of biosurfactant. PCR analysis established the presence of genes involved in synthesis of antibiotics diacetylphloroglucinol, phenazine 1-carboxylic acid and pyocyanin, and lytic enzymes chitinase and endoglucanase suggesting biocontrol potential of the isolate. Plant growth promoting activities shown by LE3 were phosphate solubilization and production of siderophores, indole acetic acid (IAA), ammonia and 1-aminocyclopropane-1-carboxylate deaminase (ACCD). To assemble all the characteristics of LE3 various bioformuations were developed. Amendment of biosurfactant in bioformulation of LE3 cells improved the shelf life. Biosurfactant amended formulation of LE3 cells was most effective in biocontrol of charcoal rot disease of sunflower and growth promotion in field conditions. The root adhered soil mass of plantlets inoculated with LE3 plus biosurfactant was significantly higher over control. Biosurfactant amended formulation of LE3 cells caused maximum yield enhancement (80.80%) and biocontrol activity (75.45%), indicating that addition of biosurfactant improves the plant-bacterial interaction and soil properties leading to better control of disease and overall improvement of plant health and yield.

Deciphering the antagonistic effect of Streptomyces spp. and host-plant resistance induction against charcoal rot of sorghum.

The findings of this study suggest that the selected five strains of Streptomyces spp. could be used for biological control of charcoal rot disease in sorghum. Two strains each of Streptomyces albus (CAI-17 and KAI-27) and Streptomyces griseus (KAI-26 and MMA-32) and one strain of Streptomyces cavourensis (SAI-13) previously reported to have plant growth-promotion activity in chickpea, rice and sorghum were evaluated for their antagonistic potential against Macrophomina phaseolina, which causes charcoal rot in sorghum. The antagonistic potential of these strains against M. phaseolina was assessed through dual culture assay, metabolite production assay, blotter paper assay in greenhouse and field disease screens. In both dual culture and metabolite production assays, the selected strains significantly inhibited the growth of M. phaseolina (63-74%). In the blotter paper assay, all the five strains of Streptomyces spp. inhibited the pathogen (80-90%). When these five strains were tested for their antagonistic potential under the greenhouse (two times) and field (two seasons) conditions by toothpick method of inoculation, significant differences were observed for charcoal rot severity. Principal component analysis capturing 91.3% phenotypic variations, revealed that the shoot samples treated with both Streptomyces and the pathogen exhibited significantly enhanced antioxidant parameters including superoxide dismutase, catalase, ascorbate peroxidase, guaiacol peroxidase, glutathione reductase, phenylalanine ammonia-lyase, polyphenol oxidase, and total phenolic contents when compared to shoot samples treated with only M. phaseolina. Scanning electron microscope analysis revealed that the phloem and xylem tissues of the Streptomyces treated stem samples were intact compared to that of pathogen inoculated plants. This study indicated that the selected strains of Streptomyces spp. have the potential for biological control of charcoal rot disease in sorghum.

Protection of Strawberry Plants against Charcoal Rot Disease (Macrophomina phaseolina) Induced by Azospirillum brasilense

Some Plant Growth-Promoting Rhizobacteria (PGPR) can induce protection against pathogens, increasing plant tolerance to various diseases. This so-called biocontrol activity is replacing harmful practices in agriculture caused by the use of agrochemicals. Azospirillum brasilense is one of the PGPR already effectively used as a resistance inducer in several crops. The aim of this study was to evaluate the protective effect of PGPR A. brasilense strains isolated from strawberry and petunia plants (REC3, 2A1, 2A2, and 2E1) against the fungal pathogen Macrophomina phaseolina, which is the causal agent of the strawberry charcoal rot disease. In vitro antagonism assays and enzymatic tests on Petri dishes revealed no direct inhibition on M. phaseolina growth by any of the A. brasilense strains. However, strawberry plants treated with REC3 and 2A1 strains increased callose and lignin deposition and stomatal closure compared to untreated plants. In addition, treatments with either bacterial strains induced a defense response in strawberry plants against virulent isolates of M. phaseolina evidenced by an increased tolerance to the charcoal rot disease. These results suggest that A. brasilense REC3 and 2A1 strains can be used for the activation of innate immunity in strawberry plants as a strategy for managing charcoal rot in a sustainable and environmentally friendly way.

Integrated management of charcoal rot disease of soybean caused by Macrophomina phaseolina

An attempt was taken for the management of charcoal rot disease of soybean caused by Macrophomina phaseolina using the integration of bio-agent with fungicide and organic amendment. Before going to the field experiments, different in-vitro trials were conducted to select a virulent isolate of M. phaseolina, an effective antagonistic isolate of Trichoderma harzianum, suitable fungicide and organic amendment. Among the seven isolates of M. phaseolina, MSP-4 isolate was selected as the test pathogen by the pathogenicity test. On the contrary, among the eighty-seven isolates of T. harzianum, ISR-26 isolate showed the highest (81.85%) inhibition of radial growth of test pathogen. In the case of fungicidal evaluation trial, Provax 200WP was found the most effective fungicide at the moderate concentration (150 ppm) but the highest conc. of Conza 5%EC and Bavistin 50WP for inhibiting the radial growth of M. phaseolina isolate MSP-4. Additionally, in vitro trial of different organic amendments, mustard oil cake was found the most active organic amendment for reducing the growth (50.92%) and development of test pathogen at 3% concentration level. In the field trial, integrated use of T. harzianum with Provax 200WP and mustard oil cake under the treatment T9 was appeared the best treatment in reducing seedling mortality (80.47%), disease incidence (80.14%) as well as disease severity (88.55%) caused by the test pathogen. Moreover, treatment T9 was the best treatment not only for management of the soybean disease but also increased the significant quantity of yield (104.42%).