Comparison of Effects of Acidic Electrolyzed Water and NaOCl on Tilletia indica Teliospore Germination

Genome-Wide Association Mapping of Virulence Genes in Wheat Karnal Bunt Fungus Tilletia indica Using Double Digest Restriction-Site Associated DNA-Genotyping by Sequencing Approach

Tilletia indica is a quarantine fungal pathogen that poses a serious biosecurity threat to wheat-exporting countries. Acquiring genetic data for the pathogenicity characters of T. indica is still a challenge for wheat breeders and geneticists. In the current study, double digest restriction-site associated-DNA genotyping by sequencing was carried out for 39 T. indica isolates collected from different locations in India. The generated libraries upon sequencing were with 3,346,759 raw reads on average, and 151 x 2 nucleotides read length. The obtained bases per read ranged from 87 Mb in Ti 25 to 1,708 Mb in Ti 39, with 505 Mb on average per read. Trait association mapping was performed using 41,473 SNPs, infection phenotyping data, population structure, and Kinship matrix, to find single nucleotide polymorphisms (SNPs) linked to virulence genes. Population structure analysis divided the T. indica population in India into three subpopulations with genetic mixing in each subpopulation. However, the division was not in accordance with the degree of virulence. Trait association mapping revealed the presence of 13 SNPs associated with virulence. Using sequences analysis tools, one gene (g4132) near a significant SNP was predicted to be an effector, and its relative expression was assessed and found upregulated upon infection.

Efficacy of Hypochlorite as a Disinfestant Against Fungal Pathogens in Agricultural and Horticultural Plant Production: A Systematic Review and Meta-Analysis

Hypochlorite is often used as a disinfestant of fungal pathogens in a range of agricultural and horticultural settings. However, reports of its effectiveness are variable across studies and it is unclear what factors could potentially influence the reported estimates of its efficacy. A systematic review and meta-analysis was conducted to assess the efficacy of hypochlorite against fungal pathogens and explore factors that may explain the observed heterogeneity in estimates of efficacy. Standardized mean effect size, Hedges' g, was calculated for each of the 109 selected studies, published from 1972 to 2019, that met the criteria defined for the systematic review. A random-effects model was used to estimate the overall mean effect size ([Formula: see text]) and determine the heterogeneity in g among studies. Hypochlorite resulted in a significant (P < 0.001) reduction in either disease intensity or propagule viability with [Formula: see text]= 2.25, suggesting a large overall effect. However, 95% prediction intervals ranged from -0.18 to 4.68, indicating that hypochlorite could be ineffective against some fungi or when targeting some substrate materials. An estimate of the within-study variability, τ², was 1.48 and the proportion of heterogeneity in g among studies due to true effects was 71.5%. Inclusion of categorical moderator variables in the random effects model showed that hypochlorite treatments were significantly (P < 0.0062) more effective when used to disinfest spores in an aqueous solution ([Formula: see text]= 4.58) than when used on plastic ([Formula: see text]= 2.13), plant ([Formula: see text]= 2.13), and wood ([Formula: see text]= 0.79). Similarly, hypochlorite treatments were significantly (P < 0.0083) more effective in disinfesting fungal propagules of Thielaviopsis spp. ([Formula: see text]= 2.51) than those of Verticillium spp. ([Formula: see text]= 1.21). A meta-regression indicated that the effect of dose (β = -3.54; P = 0.0398) and contact time (β = -0.05; P = 0.0001) on [Formula: see text] were highly significant. Further, [Formula: see text]was significantly affected by the dose × time interaction (β = -0.017; P = 0.0269). In the meta-regression models, dose and time explained 0 and 16% of the variance in true effects, respectively. In meta-regression models with a continuous variable of dose or time, a categorical variable of target or genus and their interaction term, genus and target explained an additional 7 to 19% of the variance in true effects. These results show that although the current recommended dose and contact time for commercial bleach products are expected to result in effective disinfestation, the target material and genera of the fungal pathogen of interest will likely influence their efficacy.

Accelerated Bone Induction of Adult Rat Compact Bone Plate Scratched by Ultrasonic Scaler Using Acidic Electrolyzed Water

Fresh compact bone, the candidate graft material for bone regeneration, is usually grafted for horizontal bone augmentation. However, the dense calcified structure inhibits the release of growth factors and limits cellular and vascular perfusion. We aimed to create mechano-chemically altered dense skull bone by ultrasonic treatment, along with partial demineralization using commercially available acidic electrolyzed water (AEW). The parietal skull bone of an 11-month-old Wistar rat was exposed and continuously treated with a piezoelectric ultrasonic scaler tip for 1 min, using AEW (pH 2.3) or distilled water (DW, pH 5.6) as irrigants. Treated parietal bone was removed, cut into plates (5 × 5 × 1 mm³), grafted into the back subcutaneous tissues of syngeneic rats, and explanted at 1, 2, and 3 weeks. AEW bone showed an irregular surface, deep nano-microcracks, and decalcified areas. SEM-EDS revealed small amounts of residual calcium content in the AEW bone (0.03%) compared to the DW bone (0.86%). In the animal assay, the AEW bone induced bone at 2 weeks. Histomorphometric analysis showed that the area of new bone in the AEW bone at 2 and 3 weeks was significantly larger. This new combination technique of AEW-demineralization with ultrasonic treatment will improve the surface area and three-dimensional (3D) architecture of dense bone and accelerate new bone synthesis.

The oospore stage of Plasmopara obducens, impatiens downy mildew

Impatiens downy mildew is caused by Plasmopara obducens, a pathogen known in the United States for over a hundred years, but newly attacking ornamental Impatiens walleriana in production and in the landscape. Little is known about the life cycle of P. obducens; thus, in this study an attempt was made to determine whether the pathogen is homothallic or heterothallic. Fourteen single-sporangium isolates and three single-zoospore isolates were used in single and dual inoculations of stem tissue to see whether the pathogen was homothallic or heterothallic; all isolates tested were able to produce oospores when inoculated singly, suggesting homothally. Cold treatment at 0 C for at least 1 mo induced oospores to germinate and produce primary sporangia. Inoculation of plant tissue with germinating oospores resulted in infection. Other incubation temperatures (-10, 10, and 20 C) did not induce germination, but fluctuating temperatures (between -10 and 0 C, or 0 and 10 C) induced some germination. Spores incubated at -10 C had significantly thicker walls than spores incubated at other temperatures. Evidence suggests that oospores can serve as an overwintering stage.

Effectiveness of Neutral Electrolyzed Water on Incidence of Fungal Rot on Tomato Fruits ( Solanum lycopersicum L.)

We assessed the effect of neutral electrolyzed water (NEW) on the incidence of rot on tomato ( Solanum lycopersicum L.) fruits inoculated with Fusarium oxysporum , Galactomyces geotrichum , and Alternaria sp. at sites with lesions. The inoculated fruits were treated with NEW at 10, 30, and 60 mg liter^-1 active chlorine, with copper oxychloride fungicide, and with sterile distilled water (control) for 3, 5, and 10 min. In the experiment with F. oxysporum , 50 to 80% of the control fruits and 50 to 60% of the fruits treated with the fungicide exhibited symptoms of rot at the inoculated sites. The lowest incidence recorded was 30% for fruits treated with NEW at 60 mg liter^-1 active chlorine with an immersion time of 5 min. In the experiment with G. geotrichum , incidence of rot on control fruits was 70 to 90%, and for treatment with fungicide rot incidence was 50 to 90%. NEW at 60 mg liter^-1 active chlorine significantly reduced incidence of symptomatic fruit: only 30% of the inoculated fruits washed for 5 min had damage from rot. In the experiment with Alternaria sp., 60 to 90% of the fruits in the control group and 60 to 70% of the fruits in the fungicide group were symptomatic. The lowest incidence was recorded for the treatment in which the fruits were submerged in NEW with 60 mg liter^-1 active chlorine for 3 min. In this group, 40 to 50% of the fruits exhibited symptoms of rot. These results were obtained 8 days after inoculation. NEW, with 60 mg liter^-1 active chlorine, significantly reduced incidence of rot symptoms on fruits inoculated with one of the experimental fungi relative to the control (P ≤ 0.05). NEW at 60 mg liter^-1 is effective in the control of fungal rot in tomatoes.

Electrolyzed water and its application in the food industry

Electrolyzed water (EW) is gaining popularity as a sanitizer in the food industries of many countries. By electrolysis, a dilute sodium chloride solution dissociates into acidic electrolyzed water (AEW), which has a pH of 2 to 3, an oxidation-reduction potential of >1,100 mV, and an active chlorine content of 10 to 90 ppm, and basic electrolyzed water (BEW), which has a pH of 10 to 13 and an oxidation-reduction potential of -800 to -900 mV. Vegetative cells of various bacteria in suspension were generally reduced by > 6.0 log CFU/ml when AEW was used. However, AEW is a less effective bactericide on utensils, surfaces, and food products because of factors such as surface type and the presence of organic matter. Reductions of bacteria on surfaces and utensils or vegetables and fruits mainly ranged from about 2.0 to 6.0 or 1.0 to 3.5 orders of magnitude, respectively. Higher reductions were obtained for tomatoes. For chicken carcasses, pork, and fish, reductions ranged from about 0.8 to 3.0, 1.0 to 1.8, and 0.4 to 2.8 orders of magnitude, respectively. Considerable reductions were achieved with AEW on eggs. On some food commodities, treatment with BEW followed by AEW produced higher reductions than did treatment with AEW only. EW technology deserves consideration when discussing industrial sanitization of equipment and decontamination of food products. Nevertheless, decontamination treatments for food products always should be considered part of an integral food safety system. Such treatments cannot replace strict adherence to good manufacturing and hygiene practices.

Persistence of Phytophthora ramorum in Soil Mix and Roots of Nursery Ornamentals

Although most Phytophthora species have a soilborne phase that is crucial for infection of roots and for survival away from the host, the details of the soil phase of Phytophthora ramorum are not yet fully understood. As mycelium ages, it becomes resistant to sterilization by acidic electrolyzed water (AEW), a product of the electrolysis which can be used as a disinfectant. Colonies of P. ramorum could be recovered from moist potting mix or sand for many months, whether buried as infected plant leaf tissue or as mycelium bearing chlamydospores, and the buried material was also resistant to treatment by AEW. There was no significant difference in recovery over time among treatments (sand or potting mix; infected plant tissue or mycelium); after approximately a year, colonies could be recovered at 0.8 to 14.3%. When excised roots were inoculated with P. ramorum sporangia and buried in mesh bags in potting mix, the pathogen was recovered from buried roots for at least 8 to 11 months, but it was not clear whether it was surviving as mycelium or chlamydospores. The roots of living plants of Acer macrophyllum, Buxus sempervirens, Camellia oleifera, C. sinensis, C. sasanqua, Lonicera hispidula, Taxus baccata, Umbellularia californica, Vaccinium macrocarpon, Viburnum davidii, V. tinus, V. × pragense, Rhododendron 'Gloria', and Syringa vulgaris were drenched with a sporangial solution of P. ramorum and incubated for a month; the pathogen could be recovered from roots of all plants except those of Buxus sempervirens and Lonicera hispidula. Recovery on selective agar medium (P₅ARP) was from both washed and surface-sterilized roots, suggesting that the roots were internally infected. When chlamydospores were placed near roots and observed directly, they were seen to germinate, forming sporangia. Nearby roots became infected, the tips covered with sporangia. Therefore, P. ramorum appears to have a soil phase, at least under greenhouse and nursery conditions.

Effect of acidic electrolyzed water on the viability of bacterial and fungal plant pathogens and on bacterial spot disease of tomato

Acidic electrolyzed water (AEW), known to have germicidal activity, was obtained after electrolysis of 0.045% aqueous solution of sodium chloride. Freshly prepared AEW (pH 2.3–2.6, oxidation–reduction potential 1007–1025 mV, and free active chlorine concentration 27–35 ppm) was tested in vitro and (or) on tomato foliage and seed surfaces for its effects on the viability of plant pathogen propagules that could be potential seed contaminants. Foliar sprays of AEW were tested against bacterial spot disease of tomato under greenhouse and field conditions. The viability of propagules of Xanthomonas campestris pv. vesicatoria (bacterial spot pathogen), Streptomyces scabies (potato scab pathogen), and Fusarium oxysporum f.sp. lycopersici (root rot pathogen) was significantly reduced 4–8 log units within 2 min of exposure to AEW. Immersion of tomato seed from infected fruit in AEW for 1 and 3 min significantly reduced the populations of X. campestris pv. vesicatoria from the surface of the seed without affecting seed germination. Foliar sprays of AEW reduced X. campestris pv. vesicatoria populations and leaf spot severity on tomato foliage in the greenhouse. In the field, multiple sprays of AEW consistently reduced bacterial spot severity on tomato foliage. Disease incidence and severity was also reduced on fruit, but only in 2003. Fruit yield was either enhanced or not affected by the AEW sprays. These results indicate a potential use of AEW as a seed surface disinfectant or contact bactericide.Key words: electrolyzed oxidizing water, seed disinfectant, foliar sprays, bacterial spot control.

Survival of Teliospores of Tilletia indica in Arizona Field Soils

The survival of teliospores of the Karnal bunt of wheat pathogen, Tilletia indica, was determined in field plots in Tucson, AZ. Two methods were used to test viability during a 48-month period in which 21-μm-pore-size polyester mesh bags of teliospore-infested soil were buried in irrigated and nonirrigated field plots at two sites. One method determined the total number of viable teliospores in a soil sample, regardless of whether or not they could be extracted from the soil using a sucrose centrifugation technique. The total number of viable teliospores declined over time in both irrigated and nonirrigated field plots and in the same soils in the laboratory. Based on nonlinear regressions, total number of viable teliospores decreased from 55.7% at time zero to 9.7 and 6.7% for nonirrigated and irrigated field soils, respectively, in 48 months. Total number of viable teliospores in soil in the laboratory decreased from 55.7 to 34.0% after 48 months. The second method determined germination percentages of teliospores extracted from the soil samples by means of a sucrose centrifugation technique. Based on linear regressions of transformed data, germination of teliospores extracted from irrigated and nonirrigated field soils, and control (laboratory) soil, significantly decreased over time. The rate of decrease in germination was significantly greater for teliospores from irrigated field plots than from nonirrigated plots and the laboratory soil. At time zero, 55.7% of teliospores germinated, and by 48 months, average germination of teliospores extracted from soil in nonirrigated plots had decreased to 13.6% compared with 4.4% in irrigated plots and 36.8% for teliospores in the laboratory control. Regression over time of total number of viable teliospores accounted for more of the overall variability than did regression over time of germination percentages of extracted teliospores. Neither field site nor soil depth had any effect on total number of viable teliospores or on teliospore germination percentages.

Improved Detection of Tilletia indica Teliospores in Seed or Soil by Elimination of Contaminating Microorganisms with Acidic Electrolyzed Water

Acidic electrolyzed water (AEW) is a germicidal product of electrolysis of a dilute solution (e.g., 0.4% vol/vol) of sodium chloride. This solution can be used to disinfest wheat seed or soil samples being tested for teliospores of Tilletia indica, causal agent of Karnal bunt, without risk of damaging the teliospores. The AEW used in this study had a pH of 2.5 to 2.8 and oxidation-reduction potential of approximately 1,130 mV. In simulations of routine extractions of wheat seed to detect teliospores of T. indica, the effectiveness of a 30-min AEW treatment was compared with a 2-min 0.4% sodium hypochlorite (NaOCl) treatment to eradicate bacteria and nonsmut fungi. Each treatment reduced bacterial and fungal populations in wheat seed extracts by 6 to 7 log₁₀ units when determined on 2% water agar with antibiotics. Reductions of 5 log₁₀ units or more were observed on other media. NaOCl and AEW also were very effective at eliminating bacteria and fungi from soil extracts. In studies to detect and quantitate T. indica teliospores in soil, AEW was nearly 100% effective at eliminating all nonsmut organisms. Free chlorine levels in AEW were very low, suggesting that compounds other than those with chlorine play a significant role in sanitation by AEW. The low pH of AEW was shown to contribute substantially to the effectiveness of AEW to reduce microorganisms. A standardized protocol is described for a 30-min AEW treatment of wheat seed washes or soil extracts to eliminate contaminating microorganisms. A significant advantage of the use of AEW over NaOCl is that, with AEW, teliospore germination is not reduced and usually is stimulated, whereas teliospore germination declines after contact with NaOCl. The protocol facilitates detection and enumeration of viable teliospores of T. indica in wheat seed or soil and the isolation of pure cultures for identification by polymerase chain reaction. The germicidal effects of AEW, as demonstrated in this study, illustrate the potential of AEW as an alternative to presently used seed disinfestants.

In Vitro Fungicidal Activity of Acidic Electrolyzed Oxidizing Water

Acidic electrolyzed oxidizing (EO) water, generated by electrolysis of a dilute salt solution, recently gained attention in the food industry as a nonthermal method for microbial inactivation. Our objective was to determine if EO water has potential to control foliar diseases in greenhouses. Test fungi suspended in distilled water were combined with EO water (1:9 water:EO water) for various time periods, the EO water was neutralized, and germination was assessed after 24 h. Germination of all 22 fungal species tested was significantly reduced or prevented by EO water. All relatively thin-walled species (e.g., Botrytis, Monilinia) were killed by incubation times of 30 s or less. Thicker-walled, pigmented fungi (e.g., Curvularia, Helminthosporium) required 2 min or longer for germination to be reduced significantly. Dilution of EO water with tap water at ratios of 1:4 and 1:9 (EO:tap water) decreased efficacy against Botrytis cinerea. The presence of Triton X-100 (all concentrations) and Tween 20 (1 and 10%) eliminated the activity of EO water against B. cinerea. EO water did not damage geranium leaf tissue and inhibited lesion development by B. cinerea when applied up to 24 h postinoculation. EO water has a wide fungicidal activity which could facilitate its use as a contact fungicide on aerial plant surfaces and for general sanitation in the greenhouse.

Decontaminative effect of frozen acidic electrolyzed water on lettuce

We investigated the effects of frozen acidic electrolyzed water (AcEW) on lettuce during storage in a styrene-foam container. The lettuce was kept at 2 to 3 degrees C for 24 h. Populations of aerobic bacteria associated with lettuce packed in frozen AcEW were reduced by 1.5 log CFU/g after storage for 24 h. With frozen tap water, no microorganism populations tested in this study were reduced. A frozen mixture of AcEW and alkaline electrolyzed water (AlEW) also failed to reduce populations of microorganisms associated with lettuce. Although chlorine gas was produced by frozen AcEW, it was not produced by the AcEW-AlEW mixture. This result indicates that the main factor in the decontaminative effect of frozen AcEW was the production of chlorine gas. Accordingly, low-temperature storage and decontamination could be achieved simultaneously with frozen AcEW during distribution.

Internal Transcribed Spacer Sequence-Based Phylogeny and Polymerase Chain Reaction-Restriction Fragment Length Polymorphism Differentiation of Tilletia walkeri and T. indica

ABSTRACT A polymerase chain reaction-restriction fragment length polymorphism assay to distinguish Tilleita walkeri, a rye grass bunt fungus that occurs in the southeastern United States and Oregon, from T. indica, the Karnal bunt fungus, is described. The internal transcribed spacer (ITS) region of the ribosomal DNA repeat unit was amplified and sequenced for isolates of T. indica, T. walkeri, T. horrida, and a number of other taxa in the genus Tilletia. A unique restriction digest site in the ITS1 region of T. walkeri was identified that distinguishes it from the other taxa in the genus. Phylogenetic analysis of the taxa based on ITS sequence data revealed a close relationship between T. indica and T. walkeri, but more distant relationships between these two species and other morphologically similar taxa.

Decontamination of lettuce using acidic electrolyzed water

The disinfectant effect of acidic electrolyzed water (AcEW), ozonated water, and sodium hypochlorite (NaOCl) solution on lettuce was examined. AcEW (pH 2.6; oxidation reduction potential, 1140 mV; 30 ppm of available chlorine) and NaOCl solution (150 ppm of available chlorine) reduced viable aerobes in lettuce by 2 log CFU/g within 10 min. For lettuce washed in alkaline electrolyzed water (AIEW) for 1 min and then disinfected in AcEW for 1 min, viable aerobes were reduced by 2 log CFU/g. On the other hand, ozonated water containing 5 ppm of ozone reduced viable aerobes in lettuce 1.5 log CFU/g within 10 min. It was discovered that AcEW showed a higher disinfectant effect than did ozonated water significantly at P < 0.05. It was confirmed by swabbing test that AcEW, ozonated water, and NaOCI solution removed aerobic bacteria, coliform bacteria, molds, and yeasts on the surface of lettuce. Therefore, residual microorganisms after the decontamination of lettuce were either in the inside of the cellular tissue, such as the stomata, or making biofilm on the surface of lettuce. Biofilms were observed by a scanning electron microscope on the surface of the lettuce treated with AcEW. Moreover, it was shown that the spores of bacteria on the surface were not removed by any treatment in this study. However, it was also observed that the surface structure of lettuce was not damaged by any treatment in this study. Thus, the use of AcEW for decontamination of fresh lettuce was suggested to be an effective means of controlling microorganisms.