Search

Abstract Background Postharvest diseases cause a wide loss to tomato fruits during handling and storing from harvest to consumers. Fungicides are mainly used to control postharvest diseases. Biological control is the eco-friendly substitute strategy used for postharvest diseases management as which becoming promise worldwide. Six bacterial bioagent (i.e., Bacillus subtilis, B. amyloliquefaciens, Pseudomonas resinovorans, P. alcaligenes, P. putida and P. stutzeri) were tested to suppress both Geotrichum candidum and Alternaria alternata causal agents of tomato fruit rots during storage. Results In vitro, most of bioagents significantly reduced mycelial growth rate of G. candidum. Both of B. subtilis and P. stutzeri were the most superior bacterial bioagents with values 67.03 and 72.2%, respectively. In addition, B. subtilis and B. amyloliquefaciens resulted in the most superior over all antagonists against A. alternata. The lowest percent of disease incidence and severity of G. candidum were obtained by B. subtilis and P. stutzeri. The maximum reduction percent of it on tomato fruits was recorded by applying B. subtilis and P. stutzeri with values (90 and 87%) and (91, 89%) in both seasons, respectively. Also, the highest reduction of A. alternata was obtained by using B. subtilis, which resulted in 85 and 84% in both seasons, respectively. The application of bioagents against both pathogens was significantly improved fruit quality aspects (weight loss, vitamin C, TSS and acidity %) during storage period compared to infected control fruits. Conclusion The findings revealed that both of B. subtilis and P. stutzeri could be potential biological control agents against most postharvest pathogens of tomato fruits. This might be an alternative control strategy instead of fungicides which service the sustainable and organic farming.

Abstract Background Yellow (stripe) rust, caused by Puccinia striiformis f. sp. tritici (Pst), is an economic disease of wheat. Growth-promoting fungi (GPF) such as Trichoderma asperellum and Penicillium simplicissimum have been investigated for their potential to control yellow rust and their involvement in gene expression of four PR proteins for all-stage resistance. Results Wheat plants (cv. Sids-12) treated individually with each of the biocontrol agents, P. simplicissimum and T. asperellum, at 24 and 48 hpi showed a resistance response (infection type = 2) to yellow rust, compared to the non-treated plants, which showed highly susceptible response (infection type = 9). Both biocontrol agents induced resistance against yellow rust on wheat plants, exhibiting a moderate resistance (10 MR) and reduced the colony size of Pst (0.6 mm2). Moreover, P. simplicissimum and T. asperellum increased (P ≤ 0.05) the grain yields of wheat plants infected with Pst. Scanning electron microscope (SEM) of yellow rust infected wheat leaves treated with P. simplicissimum and T. asperellum at 24 and 48 hpi showed hyperparasitism on Pst urediniospores and inhibition of the spore germination. Expressions of pathogenesis-related (PR) protein genes, PR1, PR2, PR3 and PR4 were higher in wheat plants treated with both biocontrol agents than the non-treated checks. Conclusion P. simplicissimum and T. asperellum exhibited biocontrol potential against yellow rust disease caused by P. striiformis f. sp. tritici (Pst) on wheat plants. It was found that wheat defence mechanism against Pst was activated by a high expression of PR protein genes induced by both biocontrol agents.

Abstract Background Bhendi or okra (Abelmoschus esculentus) is an important crop widely cultivated in the Indian subcontinent. The production of okra in tropical regions is constrained by several abiotic and biotic factors. Among biotic stresses, yellow vein mosaic disease (YVMD), transmitted by the whitefly (Bemisia tabaci Genn.), causes significant production losses. Results Leaves showing symptoms of YVMD were collected from okra plants in the district of Mardan, Pakistan, from which the total nucleic acid was extracted. It was found that the viral genome was 2739 bp in the length and had seven conserved open reading frames, comparable to those of monopartite begomovirus species from the Old World. Nucleotide sequence comparison revealed that the genome has 97.7% identity with bhendi yellow vein mosaic virus (BYVMV). Additionally, alpha- and betasatellite DNA components were amplified and sequenced. The alpha- and betasatellite DNA sequences were 1367 and 1346 nt in length, respectively. Sequence analysis revealed that the alpha- and betasatellite sequences shared 97.9 and 98.7% similarity with cotton leaf curl Multan alphasatellite DNA (CLCuMuA) and croton yellow vein mosaic betasatellite DNA (CroYVMB), respectively. Conclusions Based on the prevailing classification system, the isolate was identified as a variant of BYVMV, CLCuMuA, and CroYVB. Alphasatellite presence in the begomovirus betasatellite complex detected in the present study indicated a recent mobilization into the viral complex infecting okra in this region. The study findings may facilitate the design of new management strategies to protect this valuable crop against begomovirus infection.

Abstract Background Tomato mosaic virus (ToMV) is a dangerous disease of tomato (Lycopersicon esculentum) that reduces dramatically the yield. To reduce ToMV infection, microalgal isolates were utilized. Microalgal species (Chlorella vulgaris, Anabaena oryzae, Spirulina platensis, Nostoc linckia and Dunaliella salina) were shown to be responsible for the stimulation of tomato resistance against ToMV. Results Initial signs of discoloration and mosaic in ToMV-inoculated plants were detected and identified on inoculated leaves at 6 and 12 dpi in control and treated plants, respectively, suggesting that microalgae may inhibit ToMV growth. Treatment with microalgae resulted in a significant decrease in symptoms (up to 63% reduction in disease severity) and negative ELISA readings, indicating that the microalgae induced resistance in tomato against ToMV infection. The isolates also enhanced the activity of pathogenesis-related enzymes (PPO and POX reaching to 0.033 and 0.054 in D. salina, respectively), as well as tomato growth characters in comparison with the control. Microalgal treatments demonstrated that the salicylic acid (SA) and jasmonic acid (JA) pathways were involved in tomato plant defense responses. The relative gene expressions of PR1 and phenylalanine ammonia lyase (PAL), which are involved in the SA and JA pathways, respectively, were improved in treated plants compared to the control. Conclusion The findings indicated that algal-induced ToMV resistance was mediated via several defense pathways in tomato. The antiviral mechanism was described, which provides a light on the potential of algae in plant viral disease management.

Abstract Background Powdery mildew was found in most of the sunflower fields in Egypt, causing severe yellowing of the blade, petiole, stem and calyx, as well as a considerable defoliation during the summer season of 2018. Out of the fungal mycelium from infected leaves, collected from sunflower fields in the four Egyptian Governorates (Kafr El-Sheikh, Gharbia, Giza and El-Beheira), five isolates of powdery mildew pathogen were obtained and identified using morphological and molecular identification methods. Results In 2019 and 2020 seasons, five biocontrol agents (Bacillus subtilis, B. pumilus, Trichoderma harzianum, T. viride and T. koningii) were used to control powdery mildew disease on sunflower plants under field conditions compared with the fungicide (Vectra 10% SC). Treatments were significantly effective for controlling the powdery mildew disease relative to the control. The best treatment for reducing disease parameters (final disease severity (FDS%), area under disease progress curve (AUDPC) and efficacy) than the control was T. koningii. Foliar application of all the tested treatments improved plant height, head and stem diameters and seed yield in relation to untreated plants (control). The components (FDS%, AUDPC and efficacy) were extracted and described approximately 95.251% of the pooled data of seasons 2019 and 2020. In such pooled data, the principal components (PC1, PC2 and PC3) of all disease parameters, plant development parameters and yield components were recorded 76.305, 86.635 and 96.265% of the total variance, respectively. Conclusion A biological control agent, such as T. koningii, can be suggested for disease control based on the experimental findings.

Abstract Wheat stem rust causes by Puccinia graminis f. sp. tritici is a serious threat to wheat production all over the world. This study evaluated the efficacy of Bacillus subtilis, B. polymyxa and B. megaterium, Eugenol and leaf extract of Artemisia cina against the disease, and the involved mechanisms in disease resistance. B. subtilis and Eugenol treatments inhibited spore germination and increased incubation and latent periods than other treatments. Additionally, the lowest infection type, pustule length and pustule width, and receptivity (no. of pustules) were recorded in case of B. subtilis and Eugenol treatments compared with the check control. The best results in disease assessment were achieved by foliar spray application 24 h before and after inoculation. Abnormalities, lysis, collapse, and shrinking of urediniospores were recorded in treated leaves. The activities of antioxidant defense enzymes, i.e., catalase (CAT), peroxidase (POX), and polyphenoloxidase (PPO), were significantly increased in B. subtilis and Eugenol treatments. On the other hand, electrolyte leakage was decreased. The active compounds in B. subtilis were revealed by utilizing GC-MS analysis.

Abstract The influence of the inoculation with plant growth-promoting fungi (PGPF) isolates on growth enhancement of onion plants and progress of white rot disease in onions, caused by Sclerotium cepivorum, was evaluated. The tested PGPF isolates were Phoma sp. GS8-1, Phoma sp. GS 8-3, Trichoderma asperellum SKT-1, Fusarium equiseti GF18-3 and Penicillium simplicissmum GP17-2. Abnormal shape and lysis in the mycelia of the pathogen were reported in dual cultures of PGPF and S. cepivorum using scanning electron microscopy. The germination of sclerotia was reduced after soaking in culture filtrates of PGPF. The highest reduction was recorded in P. simplicissmum GP17-2 treatment (70.85%). The results demonstrated that the treatments with PGPF isolates significantly enhanced the plant height, root length, bulb perimeter and plant dry weight. Additionally, PGPF clearly reduced disease severity of white rot disease of onions. Among PGPF isolates, T. asperellum SKT-1 and P. simplicissmum GP17-2 showed the best effects in reducing the incidence and severity of white rot and enhancing onion growth. On the other hand, the levels of peroxidase and polyphenol oxidase were improved in the treated onion plants than in the untreated plants at 7 days after induction treatments. Similarly, early and strong expressions of defence genes, PR1 and PR2, were reported in plants treated with PGPF. Overall, this research suggested that PGPF treatments generated favourable effects on the suppression of white rot disease of onions.

Efficacy of plant growth promoting fungi (PGPF) has been reported as inducers for systemic resistance (ISR) against plant pathogens in different plants. This study evaluated the beneficial effects of Penicillium simplicissmum GP17-2, Penicillium sp. GP 16-2, Fusarium equiseti GF19-1 and Trichoderma asperellum SKT-1 on tobacco growth and disease suppression of potato virus Y (PVY). Tobacco plants treated with barley grain inocula of PGPF isolates had significantly higher fresh and dry weights over the untreated control plants. PGPF treated tobacco plants showed significant disease suppression under greenhouse conditions compared to control plants. Additionally, the plants under treatment with PGPF had significantly lower virus concentrations compared to the control. PGPF isolates showed variable patterns of induced activation of defense-related genes, PR-1a, Npr1 and Coi1 in tobacco, which verified the role of defense signaling pathways such as salicylic acid, ethylene and jasmonic acid in PGPF-mediated plant protection against Potato virus Y disease. [ABSTRACT FROM AUTHOR]

The study was conducted to determine the effects of cultivars susceptibility to infection with the pathogen and the pathogenic isolates on the pathogenicity of false smut fungus (Ustilaginoidea virens) and to develop new management strategies to control the pathogen. The susceptibility of 7 commercial rice cultivars to U. virens was evaluated. Moreover, pathogenicity of 10 isolates of U. virens, isolated from three governorates in Egypt was studied using Giza 171 rice cultivar. Four fungicides, four plant extracts and six bioagents were used to control U. virens under greenhouse and field conditions. Among the plant extracts, treatment with Mustard was the best in reducing infection and highly efficacy comparing with the others under greenhouse and field conditions. Chemical and biological control results were variable depending on application time, before or after pathogen inoculation. In conclusion, this study suggests the possibility of using plant extracts and bioagents for controlling U. virens infection in rice. [ABSTRACT FROM AUTHOR]

Recent trends in integrated pest management suggest that certain natural fungicides have positive effects on plant growth and disease management. This study was conducted to evaluate the possibility of using nanosilica, diatomite and bentocide instead of commercial fungicides against powdery mildew of rose. Silica nanoparticles and diatomite were applied at various concentrations to study the antifungal activity of each concentration. Application with either nanosilica at 500 mg/l water, bentocide at 2500 mg/l water, the fungicide (Penconazole) at 0.25 ml/l water or diatomite at 3000 mg/ l showed significant reductions in disease severity comparing with the other treatments. Other treatments, nanosilica at 125 and 250 mg/l water and diatomite at 1000 and 2000 mg/l water, recorded moderate reduction in disease severity. Microscopic observations revealed that silica nanoparticles caused damage effects on fungal structures of the pathogen. Based on RT-PCR, rose plants treated with nanosilica, bentocide and diatomite exhibited increased expression of phenylalanine ammonia lyase (PAL) gene. [ABSTRACT FROM AUTHOR]

Powdery and downy mildews are potentially serious diseases of cucumber inflicting considerable quantitative and qualitative losses. Efficacy of Bacillus subtilis, Pseudomonas fluorescens, Derxia gummosa and Trichoderma harzianum to control both diseases on cucumber plants under greenhouse conditions was studied. Spray of cucumber plants with suspensions of these bioagents significantly reduced severity of both mildews as well as increased fruit yield (Kg/plant) compared to the control. B. subtilis recorded highest reduction of area under disease progress curve (AUDPC), being 175.0 as compared to 536.55 in the control for powdery mildew, while T. harzianum recorded highest reduction being 241.15 as compared to the control (513.45) for downy mildew. Light and scanning electron microscopy showed that Podosphaera fusca and Pseudoperonospora cubensis spores and hyphae were abnormal and both pathogens had restricted growth on treated-cucumber plants. Additionally, treated plants showed significant increase in plant growth parameters (plant height, total chlorophyll and fresh and dry weight) and the activity of defense related enzymes (peroxidase and polyphenoloxidase) compared to the untreated plants. The results suggest the possible use of B. subtilis, T. harzianum and P. fluorescens to control powdery and downy mildews on cucumber. [ABSTRACT FROM AUTHOR]

Impact of silica (Sio2) nanoparticles against 3rd larval instar of the oriental armyworm, Mythimna separate (Walker) (Lepidoptera: Noctuidae) was tested under the laboratory conditions. As well, was the effect of the soil application with such material on resistance of wheat plants to this pest, when compared with Bacillus thuringiensis (Bt), the effective bioagent against lepidopteran pests. Nutrition proportion, longevity, growth and morality rates of treated and untreated larvae were measured. Data indicated that both treatments significantly affected the life table of this pest, but the Bt had the superiority. Feeding inhibition rate reached 37.16 and 43.91% in soil and foliar treatments with silica, respectively, while it was 70.74% in the Bt treatment. Relative growth rate approximately was decreased twice compared to the control. Larval stage period elongated from 26.30 days in control to 30.89, 30.67, 34.83 and 33.00 days in silica soil, silica foliar, Bt-foliar and Bt-Silica foliar treatments, respectively. Divergences occurred in mortality percentages of larvae between 10.00% in control, 84.63 in larvae treated with Bt and 67.69% when sprayed with silica. Furthermore, significant increase occurred in wheat plant features when silicon dioxide fertilization system was applied. In conclusion, the present results suggest the possible use of silica (Sio2) nanoparticles to control the oriental armyworm, M. separate. [ABSTRACT FROM AUTHOR]

Rice is affected by quite a number of diseases that results in high yield losses. Among the fungal diseases, kernel smut is known to occur worldwide in many countries. Biological method of plant disease management seems to be an alternative to chemical fungicides in managing rice diseases. In this study, effects of some bioagents on Tilletia barclayana, the causal agent of rice kernel smut were investigated, under greenhouse conditions. The study focused on mechanism mediating suppression of T. barclayana by investigating the effect of different bioagents on the activities of defense related enzymes, i.e peroxidase (POX), polyphenoloxidase (PPO), phenylalanine ammonia lyase (PAL). Among 15 fungal and bacterial isolates, Bacillus pumilus was found to be the most promising bioagent (BCA) for controlling the disease. Generally, the tested bioagents significantly increased the activities of defense related enzymes and total protein content compared with control treatment. Obtained data suggests use of efficient and environmentally safe bioagents to control rice kernel smut disease. [ABSTRACT FROM AUTHOR]