Damping-off Disease Research Articles

A comprehensive review of integrated management strategies for damping-off disease in chili.

Damping-off disease in chili (Capsicum annum L.) cultivation is a significant global issue, severely affecting seeds, seedlings, and young plants, regardless of the location of cultivation, whether in greenhouses or open fields. Despite chili being a widely popular vegetable used in various cuisines globally, farmers face challenges in meeting the growing demand due to the extensive damage caused by this disease, ranging from 20 to 85%. The shelf life and quality of mature pods are also severely affected. Damping-off disease is mainly caused by soil-borne fungus from the Pythium species, with additional contributions from Phytophthora, Fusarium, and Rhizoctonia species. These pathogens' adaptability to diverse environmental conditions and resistance to synthetic fungicides make controlling damping-off on a commercial scale challenging. However, integrated disease management has shown promising results as a remedial approach. In this review, we discuss the current state of chili diseases, the nature of the pathogens causing damping-off, the epidemiology of the disease, and various control mechanisms. In this review, we broadly discuss the current state of chili diseases, the nature of the pathogens causing damping-off, the epidemiology of the disease, and various control mechanisms. Furthermore, we highlight the importance and efficacy of integrated disease management techniques, along with future prospects in unexplored areas, such as host-pathogen interaction and sustainable disease control measures. The information in this review aims to assist chili growers in understanding the epidemiology and management of damping-off in chili cultivation.

BARC Biostimulant 1, a novel Streptomyces rochei C3-based formulation for disease biocontrol and plant growth promotion

Pythium aphanidermatum is a very destructive plant pathogen causing damping-off disease of vegetable seedlings in nurseries. In addition, this plant pathogenic oomycete causes seed, stem and rhizome rot, as well as post-harvest diseases. Currently, the disease management relies heavily on high dosages of chemicals like metalaxyl and copper oxychloride biocides, which are not only expensive, but are hazardous to the ecosystem. In our quest for developing a disease management strategy that is economical and safe, we isolated a strain of an actinobacterium that is highly inhibitory to P. aphanidermatum, the major cause of damping-off disease. Based on morphology and 16S rRNA sequence analysis, we identified this isolate as Streptomyces rochei. Using an LC-MS/MS analysis, the inhibitory principle has been tentatively identified as (4 S)-4,5-dihydro-4-hydroxygeldanamycin.We developed a novel formulation “BARC Biostimulant 1” using split tamarind seeds as a substrate and talcum powder as a carrier and S. rochei as the active ingredient. In P. aphanidermatum-infested soil, seed treatment and drenching resulted in about 50 % improvement in germination in greenhouse assay and protected field experiments. Under open field conditions, the germination improved to the extent of 20 %. In addition to suppression of the disease, the formulation also improved plant growth parameters like weight and height of seedlings, and induced defense responses. We further undertook multi-location replicated field trials to evaluate this purely organic formulation as a biostimulant across four states of India. Seed treatment with BARC Biostimulant 1 at the rate of 5 g/ kg seeds enhanced germination of seedlings by 80 % and enhanced fresh weight by 105 % (average of four locations), indicating a good commercial potential of this formulation.

Sustainable management of peanut damping-off and root rot diseases caused by Rhizoctonia solani using environmentally friendly bio-formulations prepared from batch fermentation broth of chitinase-producing Streptomyces cellulosae.

Soil-borne plant diseases represent a severe problem that negatively impacts the production of food crops. Actinobacteria play a vital role in biocontrolling soil-borne fungi. The target of the present study is to test the antagonistic activity of chitinase-producing Streptomyces cellulosae Actino 48 (accession number, MT573878) against Rhizoctonia solani. Subsequently, maximization of Actino 48 production using different fermentation processes in a stirred tank bioreactor. Finally, preparation of bio-friendly formulations prepared from the culture broth of Actino 48 using talc powder (TP) and bentonite in a natural as well as nano forms as carriers. Meanwhile, investigating their activities in reducing the damping-off and root rot diseases of peanut plants, infected by R. solani under greenhouse conditions. Actino 48 was found to be the most significant antagonistic isolate strain at p ≤ 0.05 and showed the highest inhibition percentage of fungal mycelium growth, which reached 97%. The results of scanning electron microscope (SEM) images analysis showed a large reduction in R. solani mycelia mass. Additionally, many aberrations changes and fungal hypha damages were found. Batch fermentation No. 2, which was performed using agitation speed of 200rpm, achieved high chitinase activity of 0.1163 U mL- 1 min- 1 with a yield coefficient of 0.004 U mL- 1 min- 1 chitinase activity/g chitin. Nano-talc formulation of Actino 48 had more a significant effect compared to the other formulations in reducing percentages of damping-off and root rot diseases that equal to 19.05% and 4.76% with reduction percentages of 60% and 80%, respectively. The healthy survival percentage of peanut plants recorded 76.19%. Furthermore, the nano-talc formulation of Actino 48 was sufficient in increasing the dry weight of the peanut plants shoot, root systems, and the total number of peanut pods with increasing percentages of 47.62%, 55.62%, and 38.07%, respectively. The bio-friendly formulations of actinobacteria resulting from this investigation may play an active role in managing soil-borne diseases.

Persistence and Microbiome Modification in Rhizoctonia solani-Inoculated Rhizosphere Following Amendment with a Bacillus Biocontrol Agent

Bacterial biocontrol agents that antagonize soilborne pathogens are increasingly considered alternatives to chemical pesticides, but their in vivo efficacy is often inconsistent, restricting commercial use. The efficacy of a biocontrol agent can depend on rhizosphere competence and its interaction with native microbiomes, which can affect ecosystem functioning. This study investigated the capacity of a Bacillus cereus sensu lato biocontrol strain (S-25) to persist on roots and in the rhizosphere of cucumber and evaluated its impact on bacterial and fungal community composition in the rhizosphere in the absence and presence of Rhizoctonia solani, the causative agent of damping-off disease in young seedlings. Following amendment, S-25 abundance in the cucumber rhizosphere decreased by two orders of magnitude but remained relatively high for the duration of the experiment, in contrast to the root surface, where it was not detected. Amendment with S-25 significantly reduced the incidence of disease caused by R. solani without reducing the relative abundance of the fungal pathogen. Interestingly, R. solani did not substantially alter the rhizosphere microbial community, whereas S-25 reduced bacterial diversity and facilitated a shift in community composition, with increased relative abundance of Acidobacteriota and Actinomycetota, and reduced abundance of Pseudomonadota, Bacteroidota, and Verrucomicrobiota. Collectively, this study provides important insights into the mode of persistence of biocontrol agents and their effect on native microbiomes in the rhizosphere of pathogen-inoculated plants. It demonstrates that amendment can significantly alter local microbiomes and suggests that optimizing amendment regimes or selecting strains with higher rhizosphere competence can enhance future biocontrol agents.

Pathogenicity and management of damping-off disease caused by Fusarium equiseti in apple (Malus × domestica Borkh.)

In 2022, apple seedlings showed symptoms of damping off with more than 50% disease incidence. The causal organism was isolated from infected seedlings which showed a white-colored mycelium with yellow to pale brown pigmentation on PDA. Additionally, microscopic observation revealed macroconidia and abundant chlamydospores in the pure culture. Based on morphology, sequences of ITS, Tef 1 alpha, and LSU genes the identity of the fungus was confirmed as Fusarium equiseti. Koch's postulates were confirmed by inoculating wheat grains infected with an isolated fungus to healthy apple seedlings. After four weeks of incubation, inoculated seedlings showed damping-off symptoms.To the best of our knowledge, this is the first report of damping-off disease of apple seedlings caused by F. equiseti from India. In-vitro evaluation of eight fungicides and nine botanicals was done against the pathogen through the poison food technique. The result revealed that fungicides Propiconazole at 1 ml L−1, Propiconazole + Difenoconazole at 1 ml L−1, Fluopyram + Tebuconazole at 0.62 ml L−1 and botanicals Curcuma longa at 5–15 % and Allium sativum at 10–15 % exhibited more than 80% inhibition therefore selected for pot studies. In pot studies, drenching of Propiconazole at 1 ml L−1 and Fluopyram + Tebuconazole at 0.62 ml L−1 three times at 15-day intervals yielded 90 % seedling survival followed by Propiconazole + Difenoconazole (83.33 %) and C. longa (5%) crude extract (56.67%). Present findings suggest that drenching of Propiconazole at 1 ml L−1 and Fluopyram + Tebuconazole at 0.62 ml L−1 are effective treatments and recommended to nursery growers for the management of damping-off in apple seedlings.

Effect of Bio Control Agents on Controlling Root Rot and Damping-off Disease of Cucumber Seedlings Caused by Rhizoctonia solani

Root rot and seedlings damping-off disease caused by Rhizoctonia solani is the most damaging disease of cucumber. This disease causes reducing yield in cucumber. This study conducted laboratory and greenhouse conditions to find out the efficacy of biological control agents, Trichoderma harzianum, Bacillus subtilis, the chemical compound Bion, and fungicide revanol. The results of pathogenicity test of R. solani on cucumber seeds showed that R. solanihas led to a significant reduction in the percentage of germination and seed rot compared to the control treatment, which amounted to 100%. The results showed the ability of all control agents used in this study to reduce the incidence of the disease. The Bion (benzothiadiazole) treatment showed significant effect and outperformed the other treatments in increasing the activity of the peroxidase enzyme, which was recorded at 14,440 (unit. minute-1.g wet weight-1). It also achieved the highest significant increase in total phenolics 1.52 (mg -1 . gram wet weight -1). Biological control agent T. harzianum has outperformed on other treatments in causing an increase in the activity of the polyphenol oxidase enzyme, it has recorded 1811.7 (unit. minute - 1 .gram of wet weight - 1 leaf).

Role of Hydrogen Peroxide (H2O2) and Trichoderma koningii in Reducing Root Rot Disease of Tomato Causing by Fusarium solani

Two isolates of the pathogenic fungus Fusarium solani the causative of tomato root rot disease named Fs1 and Fs2 were isolated from tomato plants infected with root rot disease. Results showed that both examined isolates had significant effects on the percentage of seed germination of tomato and damping-off disease. Thus, isolate Fs1 was more effective than isolate Fs2, as it recorded a percentage of germination and damping-off 56.6 and 71.6% respectively, compared to the control treatment, which recorded 100 and 0% respectively. It was found that the use of hydrogen peroxide (H2O2) at concentrations of 50, 100 and 200 ppm had a significant effect on the fungal radial growth, dry weight (DW) and sporulation of F. solani. Antifungal activity of H2O2 appeared even at the lowest concentration (50 ppm), which inhibited radial growth to 49.33%, and decreased the dry weight to 498 mg, and the sporulation to 3.75×106 spores. Additionally, the results indicated significant inhibitory effects of hydrogen peroxide (H2O2) and the bioagent Trichoderma koningii on F. solani growth. It was noticed that H2O2 has compatible effects with T. koningii, where the antagonistic ability of T. koningii against F. solani increased when the concentration of H2O2 had increased. The results revealed that the treatment F. solani + H2O2 (200 ppm) + T. koningii significantly reduced the percentage of damping-off and plant survival to 9.40 and 5.39% respectively, in comparison with the control treatment and F. solani alone treatment, which reached 20.22, 14.48, 34.32 and 67.41% respectively.

Biological control of damping-off by Fusarium oxysporum and F. verticillioides on pine and oak seedlings using edible ectomycorrhizal fungi

The Mediterranean forest has an important ecological and economic role, being holm oak (Quercus ilex), Pyrenean oak (Quercus pyrenaica), umbrella pine (Pinus pinea) and Scot pine (Pinus sylvestris) some of its main tree species. The fungal damping-off disease caused by Fusarium seriously threatens the establishment of these forest species in nurseries and reforestation, requiring the search for environmentally friendly alternatives to control the disease. We have used different species of ectomycorrhizal fungi (EMF) as potential biological control agents (BCAs) effective against the disease: Lactarius sanguifluus, Tricholoma portentosum, Suillus luteus and Agaricus silvicola from Pinus-species, and Leccinum lepidum, Amanita rubescens and Xerocomus ferrugineus from Quercus-species. A direct in vitro confrontation was performed and conidial germination of Fusarium in contact with cell-free filtrates produced by EMF was studied. Le. lepidum was the most effective Quercus-fungus in vitro against F. oxysporum, reducing its growth up to 32 % and its conidial germination up to 87 %. S. luteus was the most effective Pinus-fungus in vitro against F. oxysporum and F. verticillioides, reducing in direct confrontation, reducing its growth up to 30 %. However, La. sanguifluus was the Pinus-fungus that inhibited conidial germination of both pathogens, up to 55 %. In planta trials were carried out with seeds of the four forest species growing on substrate colonized by Le. lepidum (in Q. ilex and Q. pyrenaica seeds, infected by F. oxysporum) or by La. sanguifluus (P. pinea and P. sylvestris seeds, infected by F. oxysporum or F. verticillioides). Only La. sanguifluus was effective in reducing disease caused by F. oxysporum (strain Fo4) on P. sylvestris seeds. Therefore, EMF may be a potential tool in the control of damping-off in forest species, requiring further research.

Studies on damping-off disease of chilli seedlings caused by Pythium aphanidermatum (Edson) Fitz.

Damping off disease of chilli seedlings, a serious disease caused by Pythium aphanidermatum (Edson) Fitz. occurs in field extensively. This pathogen causes severe loss to the production of tuber as the crop destroyed at the time of seedlings. In susceptible plants seedlings losses of 25 to 75% can occur. The cost of the some of the private bred seed is very high and hence this loss assumes ecocomic importance to farmers. The present paper deals with symptoms, pathogenecity, host range etc. studies of damping off disease off chilli seedlings.

Seed biopriming with antagonistic microbes and their defense activity against damping-off disease in solanaceous vegetable crops

Seed biopriming with antagonistic microbes and their defense activity against damping-off disease in solanaceous vegetable crops

ENCAPSULATION OF SOYBEAN SEEDS WITH Actinomycetes AS A BIOCONTROL AGENT AGAINST Sclerotium rolfsii Sacc

This study evaluates the effectiveness of Actinomycetes in encapsulating soybean seeds to control damping-off disease caused by Sclerotium rolfsii. With national soybean demand reaching 22 million tons per year and domestic production only 1 million tons, increasing production is essential. One major constraint is the attack of plant pathogens such as S. rolfsii, which can cause significant losses. Actinomycetes were isolated from the rhizosphere of weeds and tested for their antagonistic activity in vitro. Seed encapsulation using various carriers (kaolin, talc, and zeolite) was conducted to determine the most effective formula. In vivo tests showed that the Actinomycetes isolate PM2 exhibited the best antagonistic activity, with the zeolite formulation reducing pre-emergence damping-off disease incidence to 12.50% and post-emergence damping-off to 8.25%, compared to the positive control. These results indicate that the use of Actinomycetes in soybean seed encapsulation is an effective and sustainable method for controlling damping-off disease. Zeolite as a carrier proved to provide a supportive environment for antagonistic microbes, maintaining moisture and supplying necessary nutrients. This research reveals the great potential of Actinomycetes as a biocontrol agent in plant disease management strategies, which can significantly enhance soybean production and support national food security.

Improving Yield of Cotton Plant by Bacillus Species as Biocontrol Agents for Damping-off Disease

Improving Yield of Cotton Plant by Bacillus Species as Biocontrol Agents for Damping-off Disease

Pythium aphanidermatum causing seedling damping-off of Hylocereus megalanthus in China.

Hylocereus megalanthus (family Cactaceae), commonly known as bird's nest fruit (Yanwo fruit), was a new tropical plant cultivated commercially in south China because of its high nutritional content and sweet taste. In August 2023, damping-off disease of approximately 60% of seedlings was observed at a nursery in Zhanjiang, Guangdong Province (E110°17'46″ N21°9'2″). Stems of infected seedlings exhibited symptoms of water-soaked tissue which caused collapse at the base of the stem and sloughing of necrotic root cortex tissue was observed (Figure 1). White aerial mycelia were visible on the surface of the stem and soil at a high relative humidity. Diseased tissues about 0.5 cm2 were taken from the infected roots and stems, surface disinfected with 75% ethanol and 3% hydrogen peroxide solution, each for 1 min, subsequently rinsed in sterile water, and placed on potato dextrose agar (PDA). Plates were incubated at 25 to 28℃ in the dark for 3 days. Coenocytic hyphae grew from all infected roots and stems. Hyphal tip transfers were completed twice, and twelve isolates with the same morphological characteristics were obtained. The colony growth on PDA was ample. Main hyphae are up to 9.5 µm wide. Sporangia were terminal, inflated, branched or unbranched. Encysted zoospores were 7.5 µm in diameter. Oogonia were terminal, globose, smooth and of 16.8 to 27.4 µm (average 21.5 µm) diameter. Oospores were typically spherical, thick-walled, yellowish, 19.7 to 26.3 µm (average 21.1 µm) diameter, wall 1 to 2 µm thick. Antheridia were mostly intercalary, sometimes terminal, broadly sac-shaped, 15.0×19.0 µm (Figure 2). The morphological features were very similar to those of Pythium spp. (Toporek and Keinath 2021). For further identification, the LSU and ITS regions of isolate CCAS-YWGCD (stored in Agricultural Culture Collection of China, ACCC 35633) were amplified and sequenced with using primer pairs LROR/LR7 and ITS1/ITS4, respectively (Gao et al. 2017; White et al. 1990). The resulting sequences were deposited in GenBank (ITS: OR775664; LSU: OR775667). BLASTn results showed 100% sequence similarity with reference sequences of Pythium aphanidermatum (AY598622 for ITS and HQ665084 for LSU). Phylogenetic tree generated from maximum likelihood analysis based on combined LSU and ITS sequence data with MEGA 10.1.8, clustered the oomycete in P. aphanidermatum clade with 100% bootstrap support (Figure 3). Therefore, the oomycete was identified as P. aphanidermatum. To confirm Koch's postulates, six three-month-old seedlings of H. megalanthus (height about 15 cm) were transplanted to 15 cm pots. Six-mm-diameter mycelial plugs obtained from 7-day-old cultures at 25℃ in the dark were buried adjacent to the stem of three unwounded healthy seedlings. Another three seedlings inoculated with PDA agar served as controls. The plants were covered with plastic bags, kept at about 30℃, and watered regularly to keep the soil moisture content high. All inoculated seedlings exhibited symptoms of stems rot and damping-off, Symptoms did not develop on the control seedlings. P. aphanidermatum by morphological and molecular analysis was reisolated from the stems. P. aphanidermatum had been reported worldwide causing disease in many agricultural crops (Qi et al. 2021; Kim et al. 2020), but this is the first report causing damping-off of H. megalanthus seedling in China as well as worldwide, and this disease should be monitored in nursery seedlings.

Trichoderma atrobrunneum: In vitro analysis of exoenzyme activity and antagonistic potential against plant pathogen from agricultural fields in the Patna region, India

Background: Fungi and oomycetes continue to be the primary source of plant diseases, which cause major crop loss factors in agriculture. Trichoderma is a genus of ascomycete fungus that lives in soil and is known for its ecological significance as a bio-fungicide. Aim: The current study aimed to assess and contrast the antagonism and exoenzyme activity of Trichoderma isolates against Pythium sp., which causes damping-off and root rot diseases on tomato plants. Trichoderma spp. was isolated from rhizospheric soil of healthy plants in the agricultural fields of Patna, Bihar district, India. Methodology: The Trichoderma isolates were evaluated for their suitability as antagonists by in vitro dual culture and non-volatile assay. Results: The results showed that the isolated Trichoderma species were effectively reduced the growth of Pythium sp. in the dual culture assay and non-volatile metabolites (12.5%, 25% and 50% v/v concentration) assay. Trichoderma atrobrunneum effectively inhibited the mycelial growth of Pythium sp. both in the dual culture (81.48%) and non-volatile metabolite assay (71.37%). Followed by Trichoderma harzianum (79.01% and 58.82%), and Trichoderma asperellum (65.43% and 50.58%) respectively. Exoenzyme activities of the Trichoderma isolates were also investigated. The antagonistic Trichoderma atrobrunneum exhibited maximum activities of β-1,3-glucanase (41.39 U/ml) and chitinase (33.06 U/ml) in comparison to T. harzianum and T. asperellum. The capacity of antagonism is enhanced by the production of the enzyme. Based on the above results, it can be said that the non-volatile metabolites and the exoenzyme of the antagonist T. species act synergistically in inhibiting Pythium growth. Conclusion: The secretion of enzymes by Trichoderma species shows that they can be used in plant disease control as novel biocontrol agents as well as to produce enzymes in biotechnological processes.

Pythium-induced damping-off disease and its management in tomato (Solanum lycopersicum L.): A review

Abstract. Pythium-induced damping-off is a disease that causes the decay of germinating seeds and young seedlings of tomato, and it is one of the most significant yield constraints for farmers in both nurseries and fields. Conventional fungicides are widely used to manage this disease, leading to two major consequences. Excessive fungicide use not only endangers human health and raises environmental concerns but also promotes the emergence of pesticide-resistant microorganisms in the environment. Consequently, there is growing interest in developing long-term damping-off management strategies that minimize reliance on conventional pesticides. To facilitate decision-making, a better understanding of pathogen biology and disease epidemiology is required. The major findings of this review works are as follows: i) Pythium-induced damping-off is an emerging disease that affects tomatoes in nurseries and fields and causes economic loss; ii) Epidemiological factors identified as most favorable for disease development include high soil moisture (70% or higher), low light, and moderate soil temperatures around 25°C.; and iii) Considerable research efforts in recent years have focused on developing bio-control solutions for damping-off, showing promising future prospects. To ensure higher tomato production, researchers and growers should manage Pythium-induced damping off in their fields. This review serves as a useful guide for the management of this disease.

Identification and Characterization of Pythium deliense Causing Sugar Beet (Beta vulgaris) Root Rot in Grand Forks, North Dakota

Damping-off disease caused by multiple species of soilborne pathogens causes severe economic losses to sugar beet production. Thus, identifying the causal agent is important to formulating effective disease management. During a July 2021 disease survey in a sugar beet field at Grand Forks, North Dakota, we observed that approximately 15% of plants located in low areas of a commercial field showed wilting leaves that were pale green and slightly blighted in color, and the roots were dark brown to black, along with irregular necrotic lesions. The isolated pathogen had the characteristic morphology of Pythium deliense. The sequences of the internal transcribed spacer (ITS) region and the cytochrome c oxidase subunit 1 mitochondrial ( cox1) genes were 100% homologous to corresponding sequences in the NCBI database, which confirmed its P. deliense identity. Moreover, the ITS phylogeny confirmed its identity as P. deliense and its close relationship with P. aphanidermatum. A disease screening trial with four sugar beet varieties was done. Growers and breeders could benefit from accurate information about the sugar beet pathogen in a given field to formulate effective disease management practices.

Phytochemical analysis and antifungal efficiency of Origanum majorana extracts against some phytopathogenic fungi causing tomato damping-off diseases

Abstract Plant diseases represent one of the major problems causing yield loss of tomato crops, especially root rot and seedling damping-off diseases caused by some phytopathogenic fungi like Fusarium solani (Fs), F. oxysporum (Fo), and Macrophomina phaseolina (Mp) frequently detected in tomato either alone or in combination infection. The objective of the present study is to assess the antifungal activity of Origanum majorana extracts against the phytopathogenic fungi, Fs, Fo, and Mp, thereby avoiding controlling the disease with chemical fungicides. In this context, the acetonic extracts of O. majorana exhibited the highest antifungal activity against the tested phytopathogens. However, F. solani exhibited high resistance to Ridomil fungicide at the tested concentrations. A chemical analysis of the O. majorana acetonic extract was conducted to determine the main phytoactive constituents exhibiting fungicidal activity. In this regard, gas chromatography and mass spectrometry confirmed that 4-terpineol was the main phytoactive compound followed by γ-terpinolene exhibiting relative percentages of 24.36 and 8.26%, respectively. These results proved that the marjoram extract may contribute to the development of an alternative and natural fungicide to protect tomato crops from damping off and root rot diseases, avoiding the usage of chemical fungicides.

Evaluation of the Efficacy of Trichoderma species and their Fungal Toxins in the Eradication of Alternaria alternata Causing Seeds Decay and Damping-off Disease on Cotton in Iraq

This study aimed to isolate and identify the pathogens accompanying the rotting and death of cotton seeds and seedlings. Also, some Trichoderma spp. were assessed against the fungal pathogen associated with the disease. The results showed that one of the essential isolated fungi, Alternaria alternata, has demonstrated high virulence in attacking cotton seeds and seedlings and reducing germination and growth. This fungus was identified based on its morphological and molecular characteristics. The Trichoderma species applied have shown high efficiency in reducing infection rates and increasing cotton germination percentage. Every isolate of Trichoderma showed a high efficiency against the fungus A. alternata by providing the highest antagonistic ability, reaching 93.75%. The highest percentage of inhibition growth of the pathogen (86.11%) was achieved by Trichoderma koningiopsis, while the lowest percentage of inhibition growth of the pathogen was 66.65 % for Trichoderma reesei. However, the biological formula prepared from species Trichoderma viride, Trichoderma pseudokoningii, Trichoderma koningiopsis and Trichoderma reesei displayed the highest percentage of inhibition of 100% against the fungus A. alternata. Keywords. Alternaria alternata; Trichoderma spp.; Trichodermin; gliotoxin; Biological control.

First record of Fusarium brachygibbosum as a causal agent of seed decay and damping-off disease on cotton in Iraq and Control using some bioagents

The results of the isolation and identification of pathogens accompanying the symptomatic seeds and seedlings of cotton showed that the most common fungus was Fusarium brachygibbosum. Molecular identification of the studied fungus was performed using the universal primers: the results of the genetic analysis revealed the identities of the fungus as follows: a 100% identity for F. brachygibbosum that was deposited at the GenBank under accession number ON738702.1. This fungus has shown high pathogenicity against cotton seeds and seedlings by severely reducing their Germination and growth and treating cotton seeds with the biological factors of Trichoderma spp. It revealed a high efficiency in reducing disease incidence and increasing cotton germination percentage. Trichoderma viride showed the highest ability to increase seed germination to 94.44%. In comparison, the lowest ability reached 77.77 % in Trichoderma pseudokoningii and Trichoderma reesei—the results of extracting toxins from the filters of Trichoderma spp. The study's use of trichodermin and Gliotoxin showed the presence of trichodermin and Gliotoxin in large quantities. The percentage of toxin inhibition was significant against the growth of pathogenic fungi. The highest percentage of inhibition was 86.1% for the isolate Trichoderma koningiopsis, and the lowest percentage was 66.65% for the isolate Trichoderma reesei. As for the effect of isolates of resistant fungus on the Pathogen in the field, the highest germination rate was 100%, and the inhibition rate was 0.00% when using the biological preparation prepared from the isolates (T. viride, T. pseudokoningii, T. koningiopsis and T. reesei). Keywords: Fusarium brachygibbosum; Trichoderma spp.; Trichodermin; gliotoxin; Biological control.

Novel Bioformulations with Trichoderma lixii to Improve the Growth Dynamics and Biocontrol of the Cowpea Damping-Off Disease

Because agricultural wastes are abundant in biologically active substances, they can be used as a substitute source to produce highly valuable products while lowering pollution levels in the environment. Therefore, we aimed at determining the best agricultural wastes to increase the biomass production rate and the effectiveness of the biocontrol strain Trichoderma lixii SARS 111 in a solid-state fermentation system. The potential for its use in enhancing growth dynamics and controlling the Fusarium oxysporum NCAIM-F-00779-caused damping-off disease of cowpea plants grown in greenhouse conditions was also studied. Using a one-factor-at-a-time experiment, five cheap agricultural waste substrates (faba bean, cowpea, sweet potato, pumpkin, and cassava) were studied using the Plackett–Burman design (PBD) and the central composite design (CCD) to optimize the nutritional and growth conditions to maximize the production of Trichoderma conidia. The findings demonstrated that increasing Candida production quantitatively required the use of 3 g of sweet potato, 3 g of cassava, pH 6, 25 °C, and pre-treatment with dH2O. The shelf life and viability of T. lixii strain were measured as log10 CFU g−1 per substrate at room temperature (RT, 25 °C) at the beginning of month 0 and subsequently at 2-month intervals for 12 months. Data showed that the fungal counts increased with the use of 4 g of sweet potato + 2 g of cassava up to 7 months and then sharply decreased, lasting up to 12 months. Additionally, this bioformulation was applied to cowpea plants in a greenhouse experiment, where a significantly higher level of plant growth traits, photosynthetic pigments, antioxidant enzymes, and chemical content in the leaves, as well as lower incidence of the damping-off disease, were noted. Accordingly, it is possible to suggest 4 g of sweet potato and 2 g of cassava as a suitable bioformulation for the industrial-scale production of the T. lixii strain, which may be a potential biocontrol agent for preventing the cowpea damping-off disease caused by F. oxysporum and improving the growth dynamics.