Severity Of Common Scab Research Articles

The effect of nanoparticles of metals and nonmetals of multicomponent trace element preparation «Avatar-2 protection» and microbial preparation «Azogran» on the incedence and severity of infectious diseases of potato

The aim of the research was to study the influence of nanoparticles (NPs) of metals and nonmetals of multicomponent trace element preparation «Avatar-2 protection» and microbial preparation «Azogran» on infectious diseases of potato in vivo. Affection of potato cultivar Suvenir Chernihivskyi by diseases was evaluated in two small plot studies on soddy podzolic soil and alkaline chernozem. Symptoms of common scab and dry rot in tubers were identified visually and then the severity and the rate of the diseases were calculated. The presence of viruses in plants was examined by agglutination tests and the rates of the viral infections were calculated. The results of the study indicate that on the soddy podzolic soil the composition of Se+I NPs significantly decrease disease severity of both common scab and dry rot by 20.00 and 17.50% respectively, whereas «Avatar-2 protection» preparation, «Azogran» preparation and the combination of «Azogran» preparation with the composition of Se+I NPs significantly decreased only the severity of dry rot by 22.50%. The combination of «Azogran» preparation with the composition of Se+I NPs significantly decreased the incidence and the disease severity of common scab, the incidence and the disease severity of dry rot on the alkaline chernozem by 40.00; 30.00; 25.00 and 30.00% respectively; whereas «Avatar-2 protection» preparation significantly decreased the incidence of viral diseases by 33.33–66.67% on both soils. The effect of the composition of Se+I NPs, «Avatar-2 protection» preparation and «Azogran» preparation is promising for further investigation. Particularly, an abundance of different groups of microorganisms in potato’s rhizosphere under the treatment with studied substances needs to be evaluated in order to understand the mechanisms diseases’ incidence and severity decrease. The effect of the studied NPs and preparations on other diseases of potato and diseases of other agricultural crops needs to be studied. The results of these studies can be useful for the development of the control methods for various infectious diseases of agricultural crops.

Tuberosphere and bulk soil microbial communities in fields differing in common scab severity are distinguished by soil chemistry and interactions with pathogens

Tuberosphere and bulk soil microbial communities in fields differing in common scab severity are distinguished by soil chemistry and interactions with pathogens

Incidence and severity of common scab of potato caused by Streptomyces scabies in Punjab, Pakistan

Incidence and severity of common scab of potato caused by Streptomyces scabies in Punjab, Pakistan

Soil bacterial community in potato tuberosphere following repeated applications of a common scab suppressive antagonist

Disease suppressive soils are important for managing soil-borne diseases that cannot be controlled with chemicals. One such disease is the potato common scab caused by Streptomyces species. Suppressiveness against common scab can develop spontaneously in fields where potato is grown for years without interruption, and this has been attributed to non-pathogenic Streptomyces strains. Streptomyces spp. have been used as inoculants in biological control, but their long-term effects have gained less attention. In our previous studies, a non-pathogenic Streptomyces strain (Str272) isolated from a potato common scab lesion suppressed common scab in field trials lasting over 5 years. In this study, bacterial communities in the tuberosphere i.e. in the soil adjacent to potato tubers, were analysed by next generation sequencing (NGS). The aim was to compare bacterial communities in untreated control plots to those in which seed tubers were treated with Str272 in one or several growing seasons. Str272 applications increased soil bacterial diversity and affected the bacterial composition in the potato tuberosphere. The most pronounced differences were observed between the untreated control and the treatments in which the antagonist had been applied in three or four consecutive years. The differences remained similar until the following growing season. Bacterial composition after repeated antagonist applications was associated with lower common scab severity. The antagonist applications had no or only slight effect on the number or abundance of OTUs belonging to Actinobacteria or Streptomyces, and no differences in quantities of pathogenic Streptomyces populations were detected by qPCR. This indicates that suppression of common scab by Str272 may not be based on direct effect on the common scab pathogens but is more likely to be associated with the alterations of the soil bacterial community. The most abundant bacteria phyla in the potato tuberosphere were Actinobacteria, Proteobacteria and Acidobacteria. However, the OTUs responding greatest to the antagonist treatments belonged to Bacterioidetes and Gemmatimonadetes. Results indicate that repeated applications of Str272 can change the bacterial community in the potato tuberosphere and lead to development of soil that is suppressive against potato common scab for several growing seasons after the last application.

Low-dose foliar treatments of the auxin analog 2,4-D reduce potato common scab and powdery scab for multiple potato cultivars and enhance root development

Common scab and powdery scab are major soilborne diseases of potato (Solanum tuberosum). The agricultural cost of both diseases is due to discounting or rejection of infected seed tubers or the formation of lesions on the surface of the tubers that make them unmarketable or, for powdery scab, yield loss. There are no widely accessible and efficacious disease management options for either common scab or powdery scab. In prior work, low-dose foliar treatment with the auxin analog herbicide 2,4-D has been shown to reduce common scab severity of select S. tuberosum cultivars in field and greenhouse settings. In the present study, we address the broad applicability of 2,4-D in disease management by testing the efficacy of 2,4-D treatment across diverse potato cultivars and in suppressing multiple scab diseases of potato. Specifically, we tested whether low-dose 2,4-D treatment is broadly efficacious on multiple white potato cultivars used in Eastern United States potato production. Additionally, we sought to determine whether 2,4-D is efficacious for mitigating powdery scab for Russet Burbank potatoes in a commercial field setting. In two years of field trials, low-dose foliar 2,4-D treatment significantly reduced common scab of all tested potato cultivars with no impact on total tuber yield. In two years of field trials in Tasmania, Australia, low-dose foliar 2,4-D treatment also reduced powdery scab of Russet Burbank potato with no impact on total tuber yield while stimulating potato plant root growth. The ability of 2,4-D to suppress two major tuber diseases and stimulate potato root growth warrants further investigation and optimization for integration into commercial growing systems.

Management and Soil Conditions Influence Common Scab Severity on Potato Tubers Via Indirect Effects on Soil Microbial Communities.

Common scab, caused by Streptomyces scabies and related species, is a potato tuber blemish disease that causes reductions in marketable yield worldwide. Evidence of suppression of common scab by indigenous soil microbial populations has been found in several studies. However, we lack a comprehensive understanding of how common scab severity relates functionally to potato varieties, farming systems, soil physical and chemical properties, and soil microbial communities. These factors may affect disease directly or indirectly by affecting one of the other variables. We performed a survey of 30 sampling locations across 12 fields in Wisconsin and used structural equation modeling to disentangle the direct effects of potato market classes, farm management (conventional versus organic), and soil physiochemical properties on common scab severity from their indirect effects mediated through soil bacterial and fungal communities. We found that, although potato market classes affected disease severity directly, the effects of farm management and soil physiochemistry were best explained as indirect, mediated by their impacts on soil bacterial communities. This suggests that evaluating the consequences of specific management practices for soil microbial communities may be useful for understanding disease pressure across fields.

Development and validation of a standard area diagram to assess common scab in potato tubers

Common scab (Streptomyces scabies) is a severe disease of the potato (Solanum tuberosum L.), which can seriously reduce the commercial value of tubers. More accurate and precise estimates of incidence and severity are required for its effective control. Standard area diagrams (SADs) were developed to aid the visual assessment of common scab severity in potato tubers. A set of 115 tuber images, with and without symptoms, was used to develop the scale, which contained 12 images of tubers with different symptoms. The SADs were then tested by 12 evaluators with no experience in appraising plant diseases, who assessed a set of 50 images 4 times, first without the aid of the SADs, then twice using the proposed scale, and then again using the scale of James (Canadian Plant Disease, 51(2), 39–65, 1971). The use of SADs increased the accuracy (coefficient of bias (Cb) = 0.99, 0.95 and 0.95 with SADs, without SADs and with the James SADs, respectively) and agreement (Lin’s coefficient (ρc) = 0.97, 0.90 and 0.88 with SADs, without SADs and with James SADs, respectively) of the severity estimates. Severity estimates were also more reproducible with the use of the scale (determination coefficient (R2) = 0.93 using SADs and R2 = 0.84 without the use of SADs). The results obtained with the scale were also repeatable (intra-rater determination coefficient (R2) = 0.94). The proposed SADs have been shown to be useful in evaluating common scab in potatoes, increasing the accuracy, precision and reliability of disease severity estimates.

Effect of Diverse Compost Products on Soilborne Diseases of Potato

ABSTRACTSoilborne diseases result in major economic losses for potato producers. Compost application can reduce soilborne diseases, however the effects of compost products on potato disease severity and incidence are still unclear. Diverse compost products were compared for their effects on soilborne diseases of potato in New Brunswick, Canada using field and growth room experiments. In the field, five products were applied at 45 Mg ha−1 dry weight to field plots in October of 2014 and 2015. In the growth room experiment, seven products were mixed to a 5% w/w ratio with naturally infested soil. Tubers were assessed for disease severity and incidence and compared with a no compost addition control. Severity of symptoms of silver scurf, black scurf (BS), common scab (CS), and powdery scab varied among treatments, experiments, and years. In the field experiment, BS severity was significantly greater in the control than in the poultry manure compost treatment (3.26% versus 0.90%) in 2016. Common scab severity and incidence in the field were positively related to soil pH and negatively related to soil particulate organic matter C and compost C concentrations. In the growth room experiment, CS severity was significantly greater in the control (8.98%) than in the municipal source separated organic compost and sea-waste compost treatments (1.72 and 2.47%, respectively). In this study, compost products had a significant, but inconsistent, suppressive effect on soilborne potato diseases. The quantity of compost C, rather than compost quality, was likely the most important factor in disease suppression in this study.

Canadian goldenrod residues and extracts inhibit the growth of Streptomyces scabiei, the causal agent of potato common scab

Common scab is one of the most important diseases affecting potato crops worldwide. Using fresh residues and/or bio-products of Canadian goldenrod (Solidago canadensis) may offer an alternative to harmful conventional fumigants. In this study, we aimed to: (i) conduct a preliminary investigation of the utilization of S. canadensis to reduce common scab severity (Experiment 1), and (ii) determine the allopathic potentials of S. canadensis extracts on Streptomyces scabiei (also known as S. scabies), the most important soil pathogen responsible for causing common scab in North America (Experiment 2). Compared with control plants, preliminary results showed that adding 1.2 kg of fresh S. canadensis residue per m2 reduced scab severity by about 45% (Experiment 1). Furthermore, hexane and dichloromethane extracts of S. canadensis, at a concentration of 200 µg·mL−1, inhibited the growth of S. scabiei by about 97% (Experiment 2). These results were comparable with those using tetracycline (2.5 µg·mL−1), a known inhibitor of S. scabiei. Both experiments suggested that S. canadensis may represent a new approach for controlling potato common scab. More studies are required to better understand the mechanisms involved in S. canadensis induced reduction of common scab in order to standardize the approaches.

Sequential analysis of soil factors related to common scab of potatoes.

The severity of common scab (CS) of potatoes has been correlated with multiple environmental factors. This study aimed at separating the effect of factors related to local conditions from those correlated to the disease development at all studied sites using a mathematical adjustment of the variables' means for site and field. The experiment was conducted at two sites differing in soil conditions, where a field with low disease severity occurs next to one with high severity. Three cultivars susceptible to CS were grown in four replicates on each field. Bacteria, actinobacteria and the txtB gene, involved in the biosynthesis of the main CS pathogenicity factor, thaxtomin, were quantified by real-time PCR. Bulk soil, tuberosphere soil and potato periderm were characterized by carbon, nitrogen, phosphorus, sulfur, calcium, magnesium and iron contents. The adjustment of the data for field effects eliminated the confounding local conditions and showed that at all fields the CS severity was negatively correlated with soil S content while the number of txtB gene copies was positively correlated with soil C and N contents. Thus, those factors might have a more general relationship to the pathogen occurrence and disease severity, which needs to be verified in other environmental conditions.

Molecular and functional characteristics of streptomycete communities in relation to soil factors and potato common scab

Naturally-occurring disease-suppressive soils provide control of plant pathogens via the activities of indigenous microbes. While all soils contain antagonistic microbes, there is little systematic understanding of the correlates of variation in indigenous antagonist populations and on their relationships with plant diseases. We characterized the population densities, inhibitory capacities, and phylogenetic composition of soil streptomycete communities in a potato field over time in relation to edaphic factors, antagonist inoculation, and potato common scab severities. Antagonistic Streptomyces populations were highly variable in time and space. Similarly, metagenomic analyses of streptomycete communities showed extensive spatial and temporal variation in composition. Soil characteristics (pH, potassium, organic matter, nitrate, and phosphorous) sometimes explained up to 50% of the spatial variation in Streptomyces population densities, proportion of inhibitory isolates, or pathogen suppressive capacity among locations in the field. Soil pH was positively correlated with common scab severity, and negatively correlated with the proportion of pathogen-inhibitory Streptomyces among locations in the field. This suggests that high pH may have direct beneficial effects on pathogen populations and disease development, and/or indirect effects on pathogen populations via reductions in pathogen-inhibitory Streptomyces populations. Mean pathogen suppressive capacity of antagonistic Streptomyces was negatively correlated with common scab disease. Streptomyces inoculants had no discernible effect on streptomycete community composition, antagonistic capacities, or potato common scab severities, likely reflecting poor colonization of inoculants. Further understanding of the relationships between indigenous antagonist populations and plant diseases will be important to harnessing the potential of indigenous communities to contribute to sustainable disease management.

Site, Year and Cultivar Effects on Relationships Between Periderm Nutrient Contents and Common Scab Severity

Common scab (CS) severity was assessed in relationship to mineral contents of potato periderm in 18 cultivars varying in maturity period and CS susceptibility. Two field experiments, one repeated in 3 years, were conducted. The effect of site, cultivar and growing period on the disease severity was always significant but not that of year to year variability. Zn, Mn and Fe periderm contents were related to site, while Ca content to cultivar effects. In both experiments, the CS severity was positively correlated to calcium and negatively to phosphorus periderm content, while correlations of CS severity to other nutrients were dependent on site or year. Since soil pH, Ca and P soil contents were not different between sites, relatively small differences in other soil chemical characteristics combined with specific cultivar nutrient requirements seemed to determine the CS severity.

Determination of factors associated with natural soil suppressivity to potato common scab.

Common scab of potatoes is a disease, which is difficult to manage due to complex interactions of the pathogenic bacteria (Streptomyces spp.) with soil, microbial community and potato plants. In Bohemian-Moravian Highlands in the Czech Republic two sites (Vyklantice and Zdirec) were selected for a study of common scab disease suppressivity. At both sites, a field with low disease severity occurs next to one with high severity and the situation was regularly observed over four decades although all four fields undergo a crop rotation. In the four fields, quantities of bacteria, actinobacteria and the gene txtB from the biosynthetic gene cluster of thaxtomin, the main pathogenicity factor of common scab, were analyzed by real-time PCR. Microbial community structure was compared by terminal fragment length polymorphism analysis. Soil and potato periderm were characterized by contents of carbon, nitrogen, phosporus, sulphur, calcium, magnesium, and iron. Quality of organic matter was assessed by high performance liquid chromatography of soil extracts. The study demonstrated that the suppressive character of the fields is locally specific. At Zdirec, the suppressivity was associated with low txtB gene copies in bulk soil, while at Vyklantice site it was associated with low txtB gene copies in the tuberosphere. The differences were discussed with respect to the effect of abiotic conditions at Zdirec and interaction between potato plant and soil microbial community at Vyklantice. Soil pH, Ca soil content or cation concentrations, although different were not in the range to predict the disease severity. Low severity of common scab was associated with low content of soil C, N, C/N, Ca and Fe suggesting that oligotrophic conditions may be favorable to common scab suppression.

Wpływ ochrony chemicznej, nawożenia organicznego oraz użyźniacza glebowego UGmax na zdrowotność bulw ziemniaka

Summary The aim of the study was to determine the effect of chemical protection, organic fertilization and UGmax soil conditioner on the healthiness of potato tubers. Satina, a medium-early potato cultivar was used for the research. Field and storage experiments were carried out in 2009–2011. Infestation of potato tubers during storage remained at a relatively low level. Occurrence of common scab and black scurf of potato was observed in the subsequent years of the study. Due to low infestation of potato tubers the statistical analysis showed no significant effects of the soil conditioner, type of chemical protection and organic fertilizers on the severity of common scab and black scurf for the subsequent years of the study. Low level of potato tubers infection by pathogens was probably the result of the medium susceptibility of the cultivar used, and unfavorable weather conditions during the growing seasons in the years of research.

Organic amendment effects on potato productivity and quality are related to soil microbial activity

Applying manure to row-crop systems can reduce inorganic fertilizer dependence and enhance soil biology and crop yields. However, it remains unclear whether low manure application rates or semi-annual application rates can provide these benefits. Our objective was to evaluate the effects of variable rates and timing of manure application on soil microbial processes and crop performance in a potato-corn cropping system. We tested the effects of five manure application rates of 0.0 (Ctrl), 1.54 (T1), 3.08 (T2), 6.16 (T3), and 12.32 (T4) Mg C ha−1 on potato productivity, severity of common scab, and soil biological processes. The highest rates of manure application consistently increased crop yields but even the lowest rate (1.54 Mg C ha−1) increased potato and corn yields. The severity of common scab incidence on daughter tubers was reduced by treatments T2, T3, and T4 in year one but was unaffected by any treatment in year two. Yield increases and reduced common scab severity were related to increased activities of C- and N-acquiring enzymes and microbial biomass C and N. Manure application rates of <2 Mg C ha−1 can provide crop and soil benefits that appear to increase with multiple applications, while higher application rates provide stronger and more consistent effects on yields, and especially soil biological properties related to nutrient cycling and organic matter dynamics.

Managing scab diseases of potato and radish caused by Streptomyces spp. using Bacillus amyloliquefaciens BAC03 and other biomaterials

Streptomyces spp. cause scab in plants like potato and radish. To effectively control this disease, biologically based materials were examined for their efficacies. In greenhouse or growth chamber tests, potting mix was infested with Streptomyces scabies (106CFUcm−3), followed by applying different products. Bacillus amyloliquefaciens strain BAC03 (105CFUcm−3) reduced disease severity and potentially enhanced growth of radish; chestnut tissues at 50% in volume, oregano and clove essential oils (0.1μgcm−3), and ground horseradish (>0.18gm−3) significantly reduced the severity of common scab in potato and/or radish. In two Michigan fields in 2011 and 2012, chestnut tissues (1.15kgm−2), oregano essential oil (1.5mlm−2), and ground horseradish (0.38gm−2) were incorporated into the soil 2weeks before planting. BAC03 (106CFUml−1, 1Lm−2) was drenched into the root zone soil 4 times at 2week intervals starting 1month after planting. BAC03 significantly reduced disease severity by 17–57% relative to control in two locations over 2years. BAC03 also enhanced potato tuber weight by 33% and 26% in 2011 in two locations. The rest of the treatments caused significant disease reduction, but were less effective compared to BAC03, and efficacy varied depending on location and year. Therefore, BAC03 can be a good biological control agent for potato common scab management.

Survey On The Incidence And Severity Of Common Scab Of Potato In Bangladesh

A survey on the incidence and severity of common scab (Streptomyces sp.) of potato was made in the major potato growing districts of Bangladesh during the cropping season of 2007-2008. A total of 150 fields was surveyed for collection of potato common scab infected samples. It was observed that there was a lot of variation in disease severity and its incidence in different districts of Bangladesh. Highest per cent scab incidence (71.41 %) was recorded in Kahalo Upazila (Bogra) and lowest (13.79 %) in Pirgacha Upazila (Rangpur). Disease incidence also varied among the tested varieties namely, Cardinal, Diamant, Granola, Binella and Raja. Highest incidence was observed in Cardinal (54.08 %) followed by Binella (50.71 %) and it was lowest in Raja (3.07 %). Cardinal and Binella were found to be highly susceptible and Raja was resistant to common scab disease. Diamant, the commercial variety showed medium susceptible reaction to the disease. J. Asiat. Soc. Bangladesh, Sci. 39(1): 35-41, June 2013 DOI: http://dx.doi.org/10.3329/jasbs.v39i1.16031

Characterizing a novel strain ofBacillus amyloliquefaciensBAC03 for potential biological control application

To identify and characterize a bacterial strain BAC03, evaluate its biological control activity against potato common scab (Streptomyces spp.) and characterize an antimicrobial substance produced by BAC03. Bacterial strain BAC03, isolated from potato common scab suppressive soil, was identified as Bacillus amyloliquefaciens by analysing sequences of fragments of the recA, recN, cheA and gyrA genes. BAC03 displayed an antagonistic activity against Streptomyces spp. on agar plates using a co-culture method. In glasshouse assays, BAC03 applied in potting mix significantly reduced common scab severity (P < 0·05) and potentially increased the growth of potato plants (P < 0·05). An antimicrobial substance extracted from BAC03 by ammonium sulfate precipitation was identified as an LCI protein using liquid chromatography-mass spectrometry. The antimicrobial activity of either a BAC03 liquid culture or the ammonium sulfate precipitate fraction was stable under a wide range of temperatures, and pH levels, as well as following incubation with several chemicals, but was reduced by all proteinases tested. Bacillus amyloliquefaciens strain BAC03 displayed a strong antimicrobial activity, that is, the suppression of potato common scab, and may potentially enhance the plant growth. LCI protein is associated with some of the antimicrobial activity. Bacterial strain BAC03 has the potential to be developed as a commercial biological control agent for potato common scab.

Effect of Manure Application Timing on Potato Yield, Quality, and Disease Incidence

This study was established to determine whether the timing of liquid dairy manure application prior to planting potatoes influenced potato crop performance and the occurrence and severity of common scab (Streptomyces spp.) and verticillium wilt (Verticillium dahliae). Four potato (Solanum tuberosum L.) varieties with varying levels of resistance to common scab and verticillium wilt were planted on a site treated with manure applied at 280,500 L ha−1 to separate plot areas 18, 6, or 1 month before potato planting in each of 2 years. Total tuber yield for 2001 showed a significant interaction between time of manure application and variety, with more scab-susceptible varieties (Russet Norkotah and W-1151R) showing lower yields compared to the fertilizer control when the manure application was made 1 month before planting. In 2002, the proportion of U.S. No. 1 tubers was significantly lower when manure was applied 1 month before planting, especially for W-1151R. Tuber dry matter was significantly reduced by manure application in both years, but was not consistently related to time of manure application. Total yield was significantly decreased as common scab levels increased, and this relationship was primarily driven by the low yield/high scab levels associated with W-1151R and Russet Norkotah planted 6 or 1 month after manure application in 2001. Late-season verticillium evaluations showed highest levels in 2001 when manure was applied 1 month before planting to susceptible varieties Superior and Russet Norkotah. This experiment showed that when manure was applied immediately ahead of potato planting yields, and quality of some varieties decreased in 1 of 2 years. Therefore, it may be safer to apply manure at least 18 months prior to planting potatoes.

Suppression of Common Scab of Potato Caused by Streptomyces turgidiscabies Using Lopsided Oat Green Manure.

Field experiments were conducted to determine the effect of green manure as fallow on common scab of potato caused by Streptomyces turgidiscabies. Significantly fewer diseased tubers were harvested from soil incorporated with lopsided oat or woolly pod vetch compared with those from oat and continuous potato cultivation in a planter experiment. Each field experiment consisted of lopsided oat cultivated during the spring and summer prior to the potato planting. Comparisons were also made with several other treatments, including cultivation of woolly pod vetch, oat, soybean, sugar beet, and potato ('Yukirasya', which is resistant to potato common potato scab) and soil application of Ferosand (Fe, mainly FeSO4, to decrease the soil pH). In field experiments conducted during 1999-2000, treatment with lopsided oat followed by lopsided oat or woolly pod vetch was significantly more effective at suppressing the disease severity than oat and continuous potato cultivation (P < 0.001). An increase in the marketable tuber ratio was also more significant than for oat and continuous potato cultivation (P < 0.001). In field experiments conducted during 2000-01, lopsided oat cultivation alone and with the application of Ferosand (1.8 t/ha) or resistant potato cultivar treatment were significantly more effective at suppressing the disease severity and incidence than sugar beet cultivation (P < 0.001), even under high disease intensity in the field. However, potato yield had a tendency to reduce after lopsided oat treatment with an application of Ferosand (1.8 t/ha) compared with lopsided oat alone or the application of Ferosand at 600 kg/ha, due to low pH conditions. In field experiments conducted during 2001-02, the lowest severity and incidence of common scab of potato were observed in soil treated with lopsided oat than with other treatments (P < 0.05 and P < 0.001, respectively). These findings suggest that lopsided oat used as fallow green manure can reduce the severity of common scab and increase potato yield.