Biological Control of Fusarium oxysporum, the Causal Agent of Fusarium Basal Rot in Onion by Bacillus spp.

Fusarium oxysporum is the main pathogen causing Fusarium basal rot in onion (Allium cepa L.), which incurs significant yield losses before and after harvest. Among management strategies, biological control is an environmentally safe and sustainable alternative to chemical control. In this study, we isolated and screened bacteria for antifungal activity against the basal rot pathogen F. oxysporum. Isolates 23-045, 23-046, 23-052, 23-055, and 23-056 significantly inhibited F. oxysporum mycelial growth and conidial germination. Isolates 23-045, 23-046, 23-052, and 23-056 suppressed the development of Fusarium basal rot in both onion seedlings and bulbs in pot and spray inoculation assays. Isolate 23-055 was effective in onion seedlings but exhibited weak inhibitory effect on onion bulbs. Based on analyses of the 16S rRNA and rpoB gene sequences together with morphological analysis, isolates 23-045, 23-046, 23-052, and 23-055 were identified as Bacillus thuringiensis, and isolate 23-056 as Bacillus toyonensis. All five bacterial isolates exhibited cellulolytic, proteolytic, and phosphate-solubilizing activity, which may contribute to their antagonistic activity against onion basal rot disease. Taken together B. thuringiensis 23-045, 23-046, 23-052, and 23-055 and B. toyonensis 23-056 have potential for the biological control of Fusarium basal rot in onion.

Identification of Fusarium Basal Rot Pathogens of Onion and Evaluation of Fungicides against the Pathogens.

Onion (Allium cepa L.) is an economically important vegetable crop worldwide. However, various fungal diseases, including Fusarium basal rot (FBR), neck rot, and white rot, reduce onion production or bulb storage life. FBR caused by Fusarium species is among the most destructive onion diseases. In this study, we identified Fusarium species associated with FBR in Jeolla and Gyeongsang Provinces in South Korea and evaluated fungicides against the pathogens. Our morphological and molecular analyses showed that FBR in onions is associated with Fusarium commune, Fusarium oxysporum, and Fusarium proliferatum. We selected seven fungicides (fludioxonil, hexaconazole, mandestrobin, penthiopyrad, prochloraz-manganese, pydiflumetofen, and tebuconazole) and evaluated their inhibitory effects on mycelial growth of the pathogens at three different concentrations (0.01, 0.1, and 1 mg/mL). We found that prochloraz-manganese was highly effective, inhibiting 100% of the mycelial growth of the pathogens at all concentrations, followed by tebuconazole. Fludioxonil showed < 50% inhibition at 1 mg/mL for the tested isolates.

Photothermally Active Core-Shell Catalyst Based on UiO-66 and Polydopamine for Highly Effective Detoxification of Nerve Agents.

A new, photothermally active, catalytic composite (Fe3O4@PD@UiO-66) based on UiO-66 and polydopamine (PD) was prepared for the decomposition of chemical warfare agents (CWAs). An iron oxide nanoparticle was introduced to enable rapid recovery after the reaction. The PD layer enabled conversion of the absorbed light into heat under infrared (IR) irradiation and increased the reaction temperature, thereby increasing the reaction rate. Dendrimer-functionalized silica particles (NH2-DS) were used as heterogeneous catalyst regenerators instead of N-ethylmorpholine. Under IR irradiation, a mixture of Fe3O4@PD@UiO-66 and NH2-DS was effective as a heterogeneous catalyst for degrading DMNP, with a 5 min half-life in water. Without IR irradiation, the half-life of DMNP was 45 min using the same catalyst mixture. Various bases including arginine, histidine, and D4 were directly modified on the surface of Fe3O4@PD@UiO-66 and used without NH2-DS or N-ethylmorpholine in order to compare their reactivities. Furthermore, a mixture of Fe3O4@PD@UiO-66 and NH2-DS was used for the decomposition of nerve agents, including sarin (GB), soman (GD), and VX, under IR-LED irradiation. Remarkably, GB was effectively decomposed with a half-life of 4.2 min, and GD demonstrated a half-life of 8.7 min. VX was hydrolyzed with a half-life of 14.0 min.

Energy-efficient recovery of fermented butyric acid using octyl acetate extraction.

BACKGROUND: A butyric acid recovery process using octyl acetate is proposed, and the design details of the extraction and subsequent distillation processes were investigated. Ternary equilibrium data for the extractor design were derived from molecular simulations and experimental measurements. RESULTS: A new procedure for estimating the thermodynamic parameters was introduced to determine the effect of the parameters on extractor design by comparison with previously reported parameters. Using the proposed recovery process with the newly estimated thermodynamic model, 99.8% butyric acid was recovered from the fermentation broth at a recovery rate of 99%. The energy demand for the proposed process was found to be lower than the average demand for several reported butyric acid recovery processes. CONCLUSIONS: The investment cost is projected to be lower than that of other butyric acid processes due to the high efficiency of extraction solvent. The recovery cost of butyric acid was comparable to its selling price.

Sensitive and Rapid Detection of Citrus Scab Using an RPA-CRISPR/Cas12a System Combined with a Lateral Flow Assay.

Citrus is the most extensively produced fruit tree crop in the world and is grown in over 130 countries. Fungal diseases in citrus can cause significant losses in yield and quality. An accurate diagnosis is critical for determining the best management practices and preventing future losses. In this study, a Recombinase polymerase amplification (RPA)-clustered regularly interspaced short palindromic repeats (CRISPR)/associated (Cas) system was established with the integration of a lateral flow assay (LFA) readout system for diagnosis of citrus scab. This detection can be completed within 1 h, is highly sensitive and prevents cross-reactions with other common fungal citrus diseases. Furthermore, the detection system is compatible with crude DNA extracted from infected plant tissue. This RPA-CRISPR/Cas12a-LFA system provides a sensitive, rapid, and cost-effective method with promising and significant practical value for point-of-care diagnosis of citrus scab. To our knowledge, this is the first report to establish an RPA- and CRISPR-based method with LFA for fungal diseases in plants.

Different Phytohormonal Responses on Satsuma Mandarin (Citrus unshiu) Leaves Infected with Host-Compatible or Host-Incompatible Elsinoë fawcettii.

Citrus scab, caused by the fungal pathogen Elsinoë fawcettii, is one of the most important fungal diseases affecting Citrus spp. Citrus scab affects young tissues, including the leaves, twigs, and fruits, and produces severe fruit blemishes that reduce the market value of fresh fruits. To study the molecular responses of satsuma mandarin (C. unshiu) to E. fawcettii, plant hormone-related gene expression was analyzed in response to host-compatible (SM16-1) and host-incompatible (DAR70024) isolates. In the early phase of infection by E. fawcettii, jasmonic acid- and salicylic acid-related gene expression was induced in response to infection with the compatible isolate. However, as symptoms advanced during the late phase of the infection, the jasmonic acid- and salicylic acid-related gene expression was downregulated. The gene expression patterns were compared between compatible and incompatible interactions. As scabs were accompanied by altered tissue growth surrounding the infection site, we conducted gibberellic acid- and abscisic acid-related gene expression analysis and assessed the content of these acids during scab symptom development. Our results showed that gibberellic and abscisic acid-related gene expression and hormonal changes were reduced and induced in response to the infection, respectively. Accordingly, we propose that jasmonic and salicylic acids play a role in the early response to citrus scab, whereas gibberellic and abscisic acids participate in symptom development.

Male-Produced Aggregation Pheromone of the Sloe Bug, Dolycoris baccarum L. (Hemiptera: Heteroptera: Pentatomidae).

The sloe bug, Dolycoris baccarum L. (Hemiptera: Heteroptera: Pentatomidae), is a Palearctic species and an important polyphagous pest. Previous studies have reported that male D. baccarum produce an aggregation pheromone, to which conspecific adults of both sexes respond. We used solid-phase microextraction (SPME) to collect volatiles released by sexually mature virgin males and females, and identified potential components of the male-produced aggregation pheromone. Analysis of the SPME samples by gas chromatography-mass spectrometry (GC-MS) revealed three male-specific components, α-bisabolol, trans-α-bergamotene, and ß-bisabolene, at a ratio of 100:10:3. A field trapping experiment showed that (±)-α-bisabolol alone attracted D. baccarum adults, and it was synergized by trans-α-bergamotene, but not (S)-ß-bisabolene. However, neither trans-α-bergamotene nor (S)-ß-bisabolene was attractive individually. A binary blend of (±)-α-bisabolol and trans-α-bergamotene in a 10:1 ratio was less attractive than caged live males, suggesting that further study is necessary to determine the absolute configuration or steroisomeric composition of the natural pheromone components. This is the first report of α-bisabolol and trans-α-bergamotene as semiochemicals among Pentatomidae, and the first to identify α-bisabolol from insects.

Reversible and cooperative photoactivation of single-atom Cu/TiO2 photocatalysts.

The reversible and cooperative activation process, which includes electron transfer from surrounding redox mediators, the reversible valence change of cofactors and macroscopic functional/structural change, is one of the most important characteristics of biological enzymes, and has frequently been used in the design of homogeneous catalysts. However, there are virtually no reports on industrially important heterogeneous catalysts with these enzyme-like characteristics. Here, we report on the design and synthesis of highly active TiO2 photocatalysts incorporating site-specific single copper atoms (Cu/TiO2) that exhibit a reversible and cooperative photoactivation process. Our atomic-level design and synthetic strategy provide a platform that facilitates valence control of co-catalyst copper atoms, reversible modulation of the macroscopic optoelectronic properties of TiO2 and enhancement of photocatalytic hydrogen generation activity, extending the boundaries of conventional heterogeneous catalysts.

Biological Control of Bacterial Fruit Blotch of Watermelon Pathogen (Acidovorax citrulli) with Rhizosphere Associated Bacteria.

Bacterial fruit blotch (BFB), which is caused by Acidovorax citrulli, is a serious threat to watermelon growers around the world. The present study was conducted to screen effective rhizobacterial isolates against 35 different A. citrulli isolates and determine their efficacy on BFB and growth parameters of watermelon. Two rhizobacterial isolates viz. Paenibacillus polymyxa (SN-22), Sinomonas atrocyanea (NSB-27) showed high inhibitory activity in the preliminary screening and were further evaluated for their effect on BFB and growth parameters of three different watermelon varieties under greenhouse conditions. The greenhouse experiment result revealed that SN-22 and NSB-27 significantly reduced BFB and had significant stimulatory effect on total chlorophyll content, plant height, total fresh weight and total dry weight compared to uninoculated plants across the tested three watermelon varieties. Analysis of the 16S ribosomal RNA (rRNA) sequences revealed that strains SN-22 belong to P. polymyxa and NSB-27 to S. atrocyanea with the bootstrap value of 99% and 98%, respectively. The isolates SN-22 and NSB-27 were tested for antagonistic and PGP traits. The result showed that the tested isolates produced siderophore, hydrolytic enzymes (protease and cellulose), chitinase, starch hydrolytic enzymes and they showed phosphate as well as zinc solubilizing capacity. This is the first report of P. polymyxa (SN-22) and S. atrocyanea (NSB-27) as biocontrol-plant growth promoting rhizobacteria on watermelon.

Bacterial community structure in maximum volatile fatty acids production from alginate in acidogenesis.

Alginate as biomass feedstock for bioconversion into volatile fatty acids (VFAs) is limited primarily by the low solubility in water or little utilization as microbial substrate and yet unknown about the microbial community structure for acidogenesis. The bacterial community structure was demonstrated the reflected changes in VFAs profiles in the maximized acidogenic process from alginate. Bacteroides- and Clostridium-related microorganisms were suggested to be mainly responsible for the hydrolysis of alginate and VFAs production, respectively. And the bacterial community shifted corresponded to VFAs producing was statistically demonstrated. A number of features discussed in this research can stimulate further interests on bioconversion of alginate into anaerobic biofuels production.

Maximization of volatile fatty acids production from alginate in acidogenesis.

In this study, the response surface methodology (RSM) was applied to determine the optimum fermentative condition of alginate with the respect to the simultaneous effects of alginate concentration and initial pH to maximize the production of total volatile fatty acids (TVFAs) and alcohols. The results showed that the alginate fermentation was significantly affected by initial pH than by alginate concentration and there was no interaction between the two variables. The optimum condition was 6.2g alginate/L and initial pH 7.6 with a maximum TVFAs yield of 37.1%. Acetic acids were the main constituents of the TVFAs mixtures (i.e., 71.9-95.5%), while alcohols (i.e., ethanol, butanol, and propanol) were not detected.

First Report of Sclerotium Rot on Cymbidium Orchids Caused by Sclerotium rolfsii in Korea.

Sclerotium rot was found on Cymbidium orchids at Seosan-si, Chungcheongnam-do, Korea, in July, 2010. Symptoms occurred on low leaves, which turned yellowish, after which the entire plant wilted. Severely infected plants were blighted and eventually died. White mycelial mats and sclerotia appeared on pseudobulbs. Based on the mycological characteristics and pathogenicity, the causal fungus was identified as Sclerotium rolfsii. This is the first report of new Sclerotium rot on Cymbidium spp. caused by S. rolfsii in Korea.

Phylogenetic analysis of Streptomyces spp. isolated from potato scab lesions in Korea on the basis of 16S rRNA gene and 16S-23S rDNA internally transcribed spacer sequences.

The 16S rRNA gene sequences for 34 strains, including 11 isolates, were determined to classify scab-causing Streptomyces spp. and relatives isolated from potato scab lesions collected in Jeju, Korea. The 16S-23S rDNA internally transcribed spacer (ITS) sequences were determined to investigate whether the 16S-23S ITS region is useful for analysing intra- and interspecific relationships in these bacteria. On the basis of phylogenetic analysis of 16S rRNA gene sequences, most of the isolates were classified as Streptomyces scabiei and Streptomyces acidiscabies. Isolate KJO61 was placed in an ambiguous taxonomic position between Streptomyces reticuliscabiei and Streptomyces turgidiscabies. 16S-23S ITS region sequence analysis showed that tRNA genes were not found in this region of Streptomyces spp. The 16S-23S ITS regions of Streptomyces spp. exhibited various lengths and highly variable sequence similarities (35-100%) within strains as well as intra- and interspecies. It was revealed that Streptomyces europaeiscabiei could be clearly differentiated from Streptomyces scabiei. However, it was clarified that ITS regions are not useful in phylogenetic analysis of Streptomyces spp.