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This study was aimed to identify major species of Streptomyces that are able to cause potato common scab in Egypt. Potato tubers showing typical symptoms of common scab disease were collected from three different regions of Upper Egypt. The causal pathogens were isolated, and morphological, biochemical and pathogenicity tests were conducted in vitro to preliminary identify the isolated Streptomyces isolates. Moreover, the partial 16S rDNA gene sequencing was used to genetically identification of the isolates. Four new pathogenic species that have not previously been reported in Egypt were identified. Four species of Streptomyces rochei, S. rutgersensis, S. lateritius, and S. bottropensis were identified. Isolates S1, S10, S14, S17, S18, S20, and S21 were identified as Streptomyces rochei, isolates S11 was identified as S. rutgersensis, isolates S13 identified as S. lateritius and isolates S15 was identified as S. bottropensis. To the obtained data, this is the first report that S. rochei, S. rutgersensis, S. lateritius, and S. bottropensis cause of potato common scab disease in Egypt. The different of obtained 16S rDNA sequences were deposited at NCBI GenBank with the following accession numbers: (S1) MZ267260, (S10) MZ267264, (S14) MZ267268, (S17) MZ267271, (S18) MZ267272, (S20) MZ267274, (S21) MZ267275, (S11) MZ267265, (S13) MZ267267, and (S15) MZ267269. The four newly identified isolates showed different pathogenicity, morphological and biochemical characteristics. [ABSTRACT FROM AUTHOR]

Common scab is an economically costly soilborne disease of potato endemic in many potato-growing regions. The disease is caused by species of Streptomyces bacteria that produce the phytotoxin thaxtomin A. The primary disease management tool available to growers is planting resistant cultivars, but no cultivar is fully resistant to common scab, and partially resistant cultivars are often not the preferred choice of growers because of agronomic or market considerations. Therefore, growers would benefit from knowledge of the presence and severity of common scab infestations in field soils to make informed planting decisions. We implemented a quantitative PCR diagnostic assay to enable field detection and quantification of all strains of Streptomyces that cause common scab in the United States through amplification of thaxtomin A biosynthetic genes. Greenhouse trials confirmed that pathogen abundance was highly correlated with disease severity for five distinct phytopathogenic Streptomyces species, although the degree of disease severity was dependent on the pathogen species. Correlations between the abundance of the thaxtomin biosynthetic genes from field soil with disease on tubers at field sites across four U.S. states and across 2 years were not as strong as correlations observed in greenhouse assays. We also developed an effective droplet digital PCR diagnostic assay that also has potential for field quantification of thaxtomin biosynthetic genes. Further improvement of the PCR assays and added modeling of other environmental factors that impact disease outcome, such as soil composition, can aid growers in making informed planting decisions. [ABSTRACT FROM AUTHOR]

Crop-specific cultivation practices including crop rotation, cover cropping, and fertilisation are key measures for sustainable farming, for which soil microorganisms are important components. This study aims at identifying links between agronomic practices, potato yield and quality as well as soil microorganisms. We analysed the roles of cover crops and of the soil prokaryotic, fungal, and protistan communities in a long-term trial, differing in crop rotation, i.e. winter wheat or silage maize as pre-crop, presence and positioning of oil radish within the rotation, and fertilisation, i.e. mineral fertiliser, straw, manure, or slurry. Up to 16% higher yields were observed when oil radish grew directly before potatoes. Losses of potato quality due to infection with Rhizoctonia solani-induced diseases and common scab was 43–63% lower when wheat + oil radish was pre-crop under manure or straw + slurry fertilisation than for maize as pre-crop. This contrast was also reflected by 42% higher fungal abundance and differences in β-diversity of prokaryotes, fungi, and protists. Those amplicon sequence variants, which were found in the treatments with highest potato qualities and differed in their abundances from other treatments, belonged to Firmicutes (2.4% of the sequences) and Mortierellaceae (28%), which both comprise potential antagonists of phytopathogens. Among protists, Lobosa, especially Copromyxa, was 62% more abundant in the high potato quality plots compared to all others, suggesting that specific higher trophic organisms can improve crop performance. Our findings suggest that successful potato cultivation is related (1) to planting of oil radish before potatoes for increasing yield and (2) to fertilisation with manure or straw + slurry for enriching the microbiome with crop-beneficial taxa. [ABSTRACT FROM AUTHOR]

Non-invasive potato defects detection has been demanded for sorting and grading purpose. Researches on the classification of the defects has been available, however, investigation on the severity level calculation is limited. For the detection of the common scab, it has been found that imaging in the infrared region provide an interesting characteristic that could distinguish defected area to normal area. Thus, investigations on this wavelength range is interesting to add more knowledge and for applications. In this research, the multispectral image has been obtained and investigated especially at three wavelengths (950, 1 150, 1 600 nm). Image pre-processing and pseudo-color conversion techniques were explored to enhance the contrast between defects, normal background skin area and soil deposits. Results show that external defects, such as common scab and some mechanical damage types, appear brighter in the near infrared region, especially at 1 600 nm against the normal skin background. It has been found that pseudo-color images conversion provides more information regarding type if surface characteristics compared to grayscale single imaging. Image segmentation using pseudo-color images after multiplication operation pre-processing could be used for common scab and mechanical damage detection excluding soil deposits with a Dice Sorensen coefficient of 0.64. In addition, image segmentation using single image at 1 600 nm shown relatively better results with Dice Sorensen coefficient of 0.72 with note that thick soil deposits will also be segmented. Defect severity level evaluation had an R2 correlation of 0.84 against standard measurements of severity.

Potato common scab (Streptomyces scabies) is a widespread disease and highly prevalent in recent years in the one cropping zone of northern China, the mixed cropping zone of southwestern China, and the two cropping zone of the Central Plains. The selection and breeding of potato common scab- resistant varieties is the most effective and economical method. The common scab resistance and the yield were evaluated for 31 potato varieties (lines) in 2022 by natural disease nursery method. In 2023, the 12 potato varieties (lines) identified in previous year were repeatedly evaluated. Among the 31 varieties (lines) tested in 2022, 11 potato varieties (lines), including 'Xisen 5', 'Z496', 'Z740', 'Z759', 'Z760', 'Z812', 'Z917', 'Z962', 'Z1148', 'Z1152' and 'Z1356', were resistant and their yields performed well. The repeated test results in 2023 showed that the 'Z962' was resistant to common scab (R) for two years, and there was no significant difference in yield compared with the local main variety 'Youjin'. The yields of 'Z1148', 'Z1152', 'Z1356', 'Z740', 'Z760' and 'Z917' were higher than those of the local main variety, but only the yield of 'Z740' was significantly different from the control, and was moderately resistant (MR) to common scab. 'Xisen 5' and 'Z496' were highly resistant to common scab and could be used as parent materials to create hybrid combinations for common scab resistance breeding. In this study, 31 potato materials were evaluated and screened for common scab resistance, which would provide basic materials for common scab resistance breeding, disease prevention and control. [ABSTRACT FROM AUTHOR]

Every land plant exists in a close relationship with microbial communities of several niches: rhizosphere, endosphere, phyllosphere, etc. The growth and yield of potato—a critical food crop worldwide—highly depend on the diversity and structure of the bacterial and fungal communities with which the potato plant coexists. The potato plant has a specific part, tubers, and the soil near the tubers as a sub-compartment is usually called the "geocaulosphere", which is associated with the storage process and tare soil microbiome. Specific microbes can help the plant to adapt to particular environmental conditions and resist pathogens. There are a number of approaches to modulate the microbiome that provide organisms with desired features during inoculation. The mechanisms of plant–bacterial communication remain understudied, and for further engineering of microbiomes with particular features, the knowledge on the potato microbiome should be summarized. The most recent approaches to microbiome engineering include the construction of a synthetic microbial community or management of the plant microbiome using genome engineering. In this review, the various factors that determine the microbiome of potato and approaches that allow us to mitigate the negative impact of drought and pathogens are surveyed. [ABSTRACT FROM AUTHOR]

Potato common scab is a common soil-borne disease worldwide, which is caused by Streptomyces spp. In order to screen Bacillus ssp. that may have a good inhibitory effect on scab pathogen, plate antibacterial tests in laboratory were conducted for determination of antibacterial activity, and the phylogenetic tree was constructed for molecular identification of Bacillus species based on gyrB sequence by neighbor joining (NJ) method. The inhibition effect of 13 strains of Bacillus on S. scabies HP4 was detected, and it was found that the inhibition zone diameter of the five strains of BEV2, BAM7, GF3, BPU6 and BMO8 on S. scabies HP4 was greater than 9.0 mm. BEV2 and GF3 were identified as B. velezensis, BAM7 as B. amyloliquefaciens, BPU6 as B. pumilus, and BMO8 as B. mojavensis based on the phylogenetic tree. The antibacterial activity of four strains of Bacillus and their combinations against three pathogenic bacteria were determined. Among them, BEV2+BAM7 had an inhibitory circle diameter of at least (29.5 ± 2.7) mm against pathogenic Streptomyces. When multiple pathogenic Streptomyces appeared simultaneously, it still showed good inhibitory effect, indicating that BEV2+BAM7 have a stable control effect on various potato common scab pathogens. In this experiment, various strains of Bacillus that antagonize different pathogenic Streptomyces are screened, which could expand the antibacterial spectrum against potato common scab and improve the stability of disease prevention and control effects. This may lays the foundation for the biological control of potato common scab and the development of biological agents. [ABSTRACT FROM AUTHOR]

Introduction and methods: As part of a study on control methods of common scab disease impact on potato yield and quality, high-throughput sequencing was used to measure the effects of soil fumigant chloropicrin alone or in combination with a Bacillus species-based biostimulant on soil bacterial diversity in terms of richness and composition, as well as on soil bacterial network interactions. Results and discussion: The results showed that common scab caused significant net yield losses of more than 46.25% in potatoes of control plots (T1), while the use of the fumigant alone (T3) and the use of the fumigant with the biostimulant (T4) reduced net yield losses to less than 2.5%. These treatments also promoted gross yield increases of 23.5 cwt. acre-1 (7.06%) and 28 cwt. acre-1 (8.41%) respectively. The study found that using the soil fumigant chloropicrin significantly and persistently altered the composition of the soil bacterial community over the growing season. The modifications of the soil bacterial community induced by the inoculation of the Bacillus species-based biostimulant are distinct by the end of the growing season depending on whether the soil has been fumigated (T4) or not (T2). Interestingly, artificial network inference analysis showed that the T2 treatment had the highest number of edges and linkages, contrary to the T3 treatment that had the lowest number of edges and linkages. The fumigation alone treatment leads to a reduction in interactions, while the application of the biostimulant, in both nonfumigated and fumigated soil, results in increased interactions and a higher number of connections within a phylum or between different taxa. Furthermore, the treatment combining the fumigant and the biostimulant exhibits a moderate increase in various network properties, providing evidence for the positive effect of biostimulant inoculation on bacterial communities in fumigated soils. Our results provide a more detailed understanding of the bacterial community structure and diversity in the soil of the different treatments. Moreover, deciphering network interactions in soil bacterial communities is fundamentally important for research in soil microbial ecology of potato cropping systems. [ABSTRACT FROM AUTHOR]

Every land plant exists in a close relationship with microbial communities of several niches: rhizosphere, endosphere, phyllosphere, etc. The growth and yield of potato—a critical food crop worldwide—highly depend on the diversity and structure of the bacterial and fungal communities with which the potato plant coexists. The potato plant has a specific part, tubers, and the soil near the tubers as a sub-compartment is usually called the “geocaulosphere”, which is associated with the storage process and tare soil microbiome. Specific microbes can help the plant to adapt to particular environmental conditions and resist pathogens. There are a number of approaches to modulate the microbiome that provide organisms with desired features during inoculation. The mechanisms of plant–bacterial communication remain understudied, and for further engineering of microbiomes with particular features, the knowledge on the potato microbiome should be summarized. The most recent approaches to microbiome engineering include the construction of a synthetic microbial community or management of the plant microbiome using genome engineering. In this review, the various factors that determine the microbiome of potato and approaches that allow us to mitigate the negative impact of drought and pathogens are surveyed.

Introduction and methodsAs part of a study on control methods of common scab disease impact on potato yield and quality, high-throughput sequencing was used to measure the effects of soil fumigant chloropicrin alone or in combination with a Bacillus species-based biostimulant on soil bacterial diversity in terms of richness and composition, as well as on soil bacterial network interactions.Results and discussionThe results showed that common scab caused significant net yield losses of more than 46.25% in potatoes of control plots (T1), while the use of the fumigant alone (T3) and the use of the fumigant with the biostimulant (T4) reduced net yield losses to less than 2.5%. These treatments also promoted gross yield increases of 23.5 cwt. acre-1 (7.06%) and 28 cwt. acre-1 (8.41%) respectively. The study found that using the soil fumigant chloropicrin significantly and persistently altered the composition of the soil bacterial community over the growing season. The modifications of the soil bacterial community induced by the inoculation of the Bacillus species-based biostimulant are distinct by the end of the growing season depending on whether the soil has been fumigated (T4) or not (T2). Interestingly, artificial network inference analysis showed that the T2 treatment had the highest number of edges and linkages, contrary to the T3 treatment that had the lowest number of edges and linkages. The fumigation alone treatment leads to a reduction in interactions, while the application of the biostimulant, in both non-fumigated and fumigated soil, results in increased interactions and a higher number of connections within a phylum or between different taxa. Furthermore, the treatment combining the fumigant and the biostimulant exhibits a moderate increase in various network properties, providing evidence for the positive effect of biostimulant inoculation on bacterial communities in fumigated soils. Our results provide a more detailed understanding of the bacterial community structure and diversity in the soil of the different treatments. Moreover, deciphering network interactions in soil bacterial communities is fundamentally important for research in soil microbial ecology of potato cropping systems.

Common scab (CS) caused by pathogenic Streptomyces spp. plays a decisive role in the qualitative and quantitative production of potatoes worldwide. Although the CS pathogen is present in Assam’s soil, disease signs and symptoms are less obvious in the landrace Rongpuria potatoes that indicate an interesting interaction between the plant and the geocaulosphere microbial population. Toward this, a comparative metagenomics study was performed to elucidate the geocaulosphere microbiome assemblages and functions of low CS-severe (LSG) and moderately severe (MSG) potato plants. Alpha diversity indices showed that CS occurrence modulated microbiome composition and decreased overall microbial abundances. Functional analysis involving cluster of orthologous groups (COG) too confirmed reduced microbial metabolism under disease incidence. The top-three most dominant genera were Pseudomonas (relative abundance: 2.79% in LSG; 12.31% in MSG), Streptomyces (2.55% in LSG; 5.28% in MSG), and Pantoea (2.30% in LSG; 3.51% in MSG). As shown by the high Pielou’s J evenness index, the potato geocaulosphere core microbiome was adaptive and resilient to CS infection. The plant growth-promoting traits and potential antagonistic activity of major taxa (Pseudomonads, non-pathogenic Streptomyces spp., and others) against the CS pathogen, i.e., Streptomyces scabiei, point toward selective microbial recruitment and colonization strategy by the plants to its own advantage. KEGG Orthology analysis showed that the CS infection resulted in high abundances of ATP-binding cassette transporters and a two-component system, ubiquitous to the transportation and regulation of metabolites. As compared to the LSG metagenome, the MSG counterpart had a higher representation of important PGPTs related to 1-aminocyclopropane-1-carboxylate deaminase, IAA production, betaine utilization, and siderophore production. [ABSTRACT FROM AUTHOR]

Potato common scab caused by the actinobacterium Streptomyces scabiei is characterized by the formation of corky lesions on tubers that reduce their marketability. Management of common scab is very complex and often ineffective under various environmental conditions. Using potato varieties that are more resistant to common scab remains one of the most efficient strategies to control this disease. However, very little is known about the factors associated with resistance to common scab. Somaclone RB9 regenerated from thaxtomin A‐habituated potato Russet Burbank calli produced tubers more resistant to common scab than the original variety. Comparison of the RB9 tuber proteome with that of Russet Burbank using label‐free quantitative proteomic analysis revealed changes in the accumulation of defence‐related proteins from the patatin and lipoxygenase (LOX) families, which are involved in the metabolism of lipids, and of two miraculins of the Kunitz‐type protease inhibitors family. The implication of LOX during common scab infection was studied using synchronized minitubers developed from leaf‐bud cuttings. S. scabiei infection stimulated the accumulation of LOX in both Russet Burbank and RB9 minitubers, but this accumulation was intensified in RB9 minitubers. Infection also increased LOX activity in Russet Burbank and RB9 minitubers. However, LOX activity measured in noninfected RB9 minitubers was similar to that of infected Russet Burbank minitubers, indicating endogenous activation of LOX activity in RB9 minitubers. We discuss how increased LOX abundance and activity in the somaclone RB9 may contribute to improving tuber defence against common scab. [ABSTRACT FROM AUTHOR]

The phytotoxin thaxtomin A (TA) is the key pathogenicity factor synthesized by the bacteria Streptomyces scabiei, the main causal agent of common scab of potato (Solanum tuberosum L.). TA treatment of potato tuber flesh produces a brown color that was attributed to necrosis. The intensity of TA-induced browning was generally thought to correlate with potato sensitivity to the disease. In this study, we found that TA-induced browning was much more intense in the potato tuber flesh of the common scab moderately resistant variety Russet Burbank (RB) than that observed in tubers of the disease-susceptible variety Yukon Gold (YG). However, there was no significant difference in the level of TA-induced cell death detected in both varieties, suggesting that tubers response to TA does not correlate with the level of sensitivity to common scab. TA-treated potato tuber tissues accumulated significantly higher levels of phenolic compounds than untreated controls, with a higher phenol content detected in RB TA-treated tissues than in those of YG. Browning was associated with a significant induction of the expression of genes of the phenylpropanoid pathway in RB tubers, indicating that TA activated this metabolic pathway. These results suggest that tuber flesh browning induced by TA is due to the accumulation of phenolic compounds. These phenolics may play a role in the protection of potato tubers against S. scabiei. [ABSTRACT FROM AUTHOR]

Beneficial soil and crop management practices, such as longer rotations, cover crops and green manures, organic amendments, and reduced tillage, may improve soil and crop health and productivity when incorporated into cropping systems. Long-term trials are needed to assess the full impacts and effects of these systems. In field trials originally established in 2004, three different 3-yr potato cropping systems focused on management goals of soil conservation (SC), soil improvement (SI), and disease suppression (DS) were evaluated and compared to a standard 2-yr rotation (SQ) and a nonrotation control (PP). After 12–15 years and results compiled over a four-year period (2015–2018), the SI system (with history of compost amendments) increased total and marketable tuber yields relative to all other systems, with yields averaging 26 to 36% higher than the standard SQ system and 36 to 59% greater than PP. SI also improved soil properties such as organic matter and soil water content, nutritional characteristics, and microbial activity compared to the other systems. The SI system continued to provide these improvements several years after compost amendments ended, indicating the long-term benefits. The DS system, which included a disease-suppressive green manure rotation crop and fall cover crops, also improved yield (by 16–20%), had higher organic matter content (by 12%), and increased microbial activity (by 22%) relative to SQ, as well as reducing the soilborne tuber diseases black scurf and common scab by 10–30%. The nonrotation PP system resulted in the notable degradation of soil properties and yield over time. These results demonstrate that soil health management practices can be effectively incorporated into viable potato cropping systems to improve soil properties and crop health, and may enhance long-term sustainability. [ABSTRACT FROM AUTHOR]

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Potato common scab (CS) is a worldwide soil-borne disease that severely reduces tuber quality and market value. We observed that foliar application of tryptophan (Trp) could induce resistance against CS. However, the mechanism of Trp as an inducer to trigger host immune responses is still unclear. To facilitate dissecting the molecular mechanisms, the transcriptome of foliar application of Trp and water (control, C) was compared under Streptomyces scabies (S) inoculation and uninoculation. Results showed that 4867 differentially expressed genes (DEGs) were identified under S. scabies uninoculation (C-vs-Trp) and 2069 DEGs were identified under S. scabies inoculation (S-vs-S+Trp). Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses indicated that Trp induced resistance related to the metabolic process, response to stimulus, and biological regulation. As phytohormone metabolic pathways related to inducing resistance, the expression patterns of candidate genes involved in salicylic acid (SA) and jasmonic acid/ethylene (JA/ET) pathways were analyzed using qRT-PCR. Their expression patterns showed that the systemic acquired resistance (SAR) and induced systemic resistance (ISR) pathways could be co-induced by Trp under S. scabies uninoculation. However, the SAR pathway was induced by Trp under S. scabies inoculation. This study will provide insights into Trp-induced resistance mechanisms of potato for controlling CS, and extend the application methods of Trp as a plant resistance inducer in a way that is cheap, safe, and environmentally friendly. [ABSTRACT FROM AUTHOR]

Potato common scab is an important bacterial disease afflicting potatoes around the world. Better knowledge of the local Streptomyces spp. populations causing this disease is key to developing durable control strategies. In this study, we isolated 230 Streptomyces strains from scab-infected potato tubers harvested from commercial potato fields located across the province of Quebec, Canada. The genetic diversity of this collection was first studied using repetitive element-based PCR fingerprinting, and the genomes of 36 representative strains were sequenced using PacBio's sequencing technology. This enabled us to identify the strains to the species level, to study the distribution of previously characterized virulence-associated genes and clusters, and to explore the repertoires of putative plant cell wall-degrading enzymes. In parallel, the virulence of the 36 strains was evaluated using a potato tuber slice assay. The diversity was higher than previously reported, as eleven phytopathogenic species were found across the province. Among them, S. scabiei and S. acidiscabies were the most abundant as well as the most virulent. Strains belonging to these two species harbored numerous virulence determinants, including the thaxtomin biosynthetic gene cluster. By contrast, most weakly virulent strains lacked this cluster but harbored at least one known virulence determinant. The results obtained suggest that a higher number of virulence-associated genes and clusters in the genome of phytopathogenic Streptomyces spp. is associated with greater virulence. This study contributes to increasing the publicly available genomic resources of scab-causing Streptomyces spp., and expand our knowledge on the diversity and virulence of this important bacterial pathogen.

Bactericides Krosin AG and Timsen; fungicides Oxicob, Micra 72WP, Provex 200WP, and Amister Top; and plant nutrients Mag Plus and Alpha Boron Plus were evaluated against Streptomyces scabies in vitro and under field conditions. Among the chemicals, Oxicob (3500 ppm) and Krosin AG (2000 ppm) demonstrated maximum zone of inhibition against S. scabies by 20.61 and 19.74 mm, respectively in in vitro. In field, maximum reduction of common scab incidence by number (64.99%) & weight (66.02%), and severity (73.53%) was achieved by Oxicob. Along with the reduction of common scab incidence by number (49.92%) & weight (47.70%), and severity (49.47%), Alpha Boron Plus resulted the highest potato tuber yield (18.07 ton ha−1) in comparison to other chemicals. The present study suggests that combination of Oxicob and Alpha Boron Plus can be applied in the field to increase potato tuber yield. [ABSTRACT FROM AUTHOR]

Adequate integrated management of potato leaf diseases can have an influence on pathogens which are challenging to control and cause main potato tuber diseases. Deriving from this hypothesis, an experiment was designed to evaluate the efficacy of foliar application of twelve fungicides on late blight in tubers, common scab, black scurf and silver scurf. In the period of 2013 to 2017, the fungicides were equally applied six times in registered doses during the growing seasons. Eight tuber disease indicators and eight yield characteristics were then evaluated in harvested tuber samples. Significant differences were found among the fungicides used. In comparison to the negative control (n. c.), the application of Infinito, Ranman Top and Revus Top reduced the quantity of tubers infected by late blight by 72% on average. The incidence of common scab increased by 65% of n. c. under the effect of copper oxychloride, while an average reduction by 19% of n. c. was observed with the use of Acrobat MZ WG, Curzate Gold and Consento. The occurrence of silver scurf was significantly enhanced by Curzate Gold and Consento (105% of n. c.), while it was suppressed by Revus Top and Revus (85% of n. c.). All fungicides were ineffective on black scurf yet had a positive influence on the potato yield and quality, with the choice of fungicide having a great impact on the quality of tubers. The application of any safe fungicide is important, especially in years similar to 2015, which was the most devastating recent year for potato production in terms of structural changes in yield of tubers. [ABSTRACT FROM AUTHOR]

The purpose of the research is to analyze situation with control measures against animals with ectoparasitoses by the means of bringing environmentally safe and easy to use medicinal products to animal industry. Materials and methods. Literature has been studied and situation on extension of the major parasitic arthopods in animals have been analyzed in the Republic of Belarus. Evaluation of results of administration of Stomozan, Ektocin-5, Ratoks, Pharmacidol-600 as well as Rivertin, Univerm, aversectin paste and Pharmacine. Results and discussion. It is necessary to carry out disinfestation of outer walls, summer sheds, fences by the means of Stomozan, Ektocin-5, Ratoks, Pharmacidol-600 in order to eliminate parasitic insects and mites. Animals might be treated by these drugs. During the winter animals are treated by insect-powder, unctures, liniments. At the onset of warm weather animals are treated by liquid acaricides at all times. Drugs from the pyrethroids, macrocyclic lactone, organic sulphur-containing compound groups are administered more frequent. But summer spraying do not guarantee 100 % impact against gadfly diseases. For horse treatment Rivertin can be used in the dose of 0.1 mg per kg of animal body weight per os with food dualfold in 24 hours; Univerm can be used in the dose of 0.1 mg per kg per os with food dualfold in 24 hours; 2% Aversectin paste can be used in the dose of 1 g per 100 kg of body weight per os dualfold every other day. Pharmacine in the single dose of 0.4 ml (2 injections of 0.2 ml) intradermally in the neck is recommended to use for treatment of hypodermatosis. Intradermal administration of Pharmacine is effective during the period from September, 15 to March (as far as swellings are appeared under the skin). If larvae formed velum under the skin, the dose should be increased.

The phytotoxin thaxtomin A (TA) is the key pathogenicity factor synthesized by the bacteria Streptomyces scabiei, the main causal agent of common scab of potato (Solanum tuberosum L.). TA treatment of potato tuber flesh produces a brown color that was attributed to necrosis. The intensity of TA-induced browning was generally thought to correlate with potato sensitivity to the disease. In this study, we found that TA-induced browning was much more intense in the potato tuber flesh of the common scab moderately resistant variety Russet Burbank (RB) than that observed in tubers of the disease-susceptible variety Yukon Gold (YG). However, there was no significant difference in the level of TA-induced cell death detected in both varieties, suggesting that tubers response to TA does not correlate with the level of sensitivity to common scab. TA-treated potato tuber tissues accumulated significantly higher levels of phenolic compounds than untreated controls, with a higher phenol content detected in RB TA-treated tissues than in those of YG. Browning was associated with a significant induction of the expression of genes of the phenylpropanoid pathway in RB tubers, indicating that TA activated this metabolic pathway. These results suggest that tuber flesh browning induced by TA is due to the accumulation of phenolic compounds. These phenolics may play a role in the protection of potato tubers against S. scabiei.

Beneficial soil and crop management practices, such as longer rotations, cover crops and green manures, organic amendments, and reduced tillage, may improve soil and crop health and productivity when incorporated into cropping systems. Long-term trials are needed to assess the full impacts and effects of these systems. In field trials originally established in 2004, three different 3-yr potato cropping systems focused on management goals of soil conservation (SC), soil improvement (SI), and disease suppression (DS) were evaluated and compared to a standard 2-yr rotation (SQ) and a nonrotation control (PP). After 12–15 years and results compiled over a four-year period (2015–2018), the SI system (with history of compost amendments) increased total and marketable tuber yields relative to all other systems, with yields averaging 26 to 36% higher than the standard SQ system and 36 to 59% greater than PP. SI also improved soil properties such as organic matter and soil water content, nutritional characteristics, and microbial activity compared to the other systems. The SI system continued to provide these improvements several years after compost amendments ended, indicating the long-term benefits. The DS system, which included a disease-suppressive green manure rotation crop and fall cover crops, also improved yield (by 16–20%), had higher organic matter content (by 12%), and increased microbial activity (by 22%) relative to SQ, as well as reducing the soilborne tuber diseases black scurf and common scab by 10–30%. The nonrotation PP system resulted in the notable degradation of soil properties and yield over time. These results demonstrate that soil health management practices can be effectively incorporated into viable potato cropping systems to improve soil properties and crop health, and may enhance long-term sustainability.

Potato common scab caused by Streptomyces scabies is one of the most economically important diseases infecting potato. It reduces the quality of potato tubers, which subsequently decreases the tuber prices and causes significant economic losses for potato growers. Biological control using bacteriophages is a promising strategy for controlling this disease. In this study, a novel bacteriophage with high lytic efficacy against S. scabies was isolated from a potato field at El-Minya, Egypt, and was designated SscP1EGY. The phage has an icosahedral head of 55 nm and a short tail of 7.5 nm, typical of a podovirus. Its infection cycle was 90 min, including 50 min of latent time and 40 min of rise period with a burst size of approximately 200 PFU per infected cell. The genome of SscP1EGY consists 51,751 nucleotides with 76 predicted genes. SscP1EGY infected and completely lysed seven tested S. scabies strains but showed no lytic activity against three beneficial Streptomyces species, other beneficial bacterial species, and non-target plant pathogenic bacteria. In greenhouse experiments, treatment of S. scabies-inoculated potato tubers with phage SscP1EGY resulted in reductions of (1) the severity of scab, (2) the number of lesions, and (3) the percentage of lesion surface, as compared to the inoculated tubers without phage treatment. Also, scab lesions appeared superficial in phage-treated tubers but pitted in non-phage-treated tubers. Our results suggest that SscP1EGY has a potential as a biological control agent for S. scabies. Based on our knowledge, SscP1EGY is the first sequenced S. scabies-infecting phage in Egypt. [ABSTRACT FROM AUTHOR]

Common scab of potato causes important economic losses worldwide following the development of necrotic lesions on tubers. In this study, the genomes of 14 prevalent scab-causing Streptomyces spp. isolated from Prince Edward Island, one of the most important Canadian potato production areas, were sequenced and annotated. Their phylogenomic affiliation was determined, their pan-genome was characterized, and pathogenic determinants involved in their virulence, ranging from weak to aggressive, were compared. 13 out of 14 strains clustered with Streptomyces scabiei , while the last strain clustered with Streptomyces acidiscabies. The toxicogenic and colonization genomic regions were compared, and while some atypical gene organizations were observed, no clear correlation with virulence was observed. The production of the phytotoxin thaxtomin A was also quantified and again, contrary to previous reports in the literature, no clear correlation was found between the amount of thaxtomin A secreted, and the virulence observed. Although no significant differences were observed when comparing the presence/absence of the main virulence factors among the strains of S. scabiei , a distinct profile was observed for S. acidiscabies. Several mutations predicted to affect the functionality of some virulence factors were identified, including one in the bldA gene that correlates with the absence of thaxtomin A production despite the presence of the corresponding biosynthetic gene cluster in S. scabiei LBUM 1485. These novel findings obtained using a large number of scab-causing Streptomyces strains are challenging some assumptions made so far on Streptomyces' virulence and suggest that other factors, yet to be characterized, are also key contributors. [ABSTRACT FROM AUTHOR]

In North America, potato early dying is often controlled using soil fumigants. Fumigants confer benefits on plant health but also impact soil microbial activity, including nitrogen (N) cycling. The purpose of this study was to evaluate the effects of two soil fumigants, chloropicrin and metam sodium, on potato crop yield, N uptake, and N use efficiency (NUE), as well as soilborne pathogens, soil microbial respiration rates and soil concentrations of NH4+-N and NO3−-N. We established a field study with a split-plot randomized complete block design in 2016 and 2017, with whole plots divided among three fumigation treatments (no fumigant, chloropicrin, or metam sodium) and split into five subplots, each receiving a different total application rate of N (45, 135, 202, 269, or 336 kg·ha−1 N). Both fumigants suppressed Verticillium dahliae propagule concentrations and foliar symptoms of potato early dying while increasing yield, final tuber set, N uptake, and NUE. Fumigation did not affect the agronomic optimum N rate, nor the response of marketable yield to N rate, but it did increase yield per unit N applied (partial factor productivity) by 16% and 35% over the non-fumigated controls in 2016 and 2017, respectively. Chloropicrin, but not metam sodium, reduced the prevalence of common scab symptoms in tubers. Both fumigants decreased microbial respiration rates before planting and at midseason. Fumigants reduced nitrification rates before planting and at midseason, with chloropicrin having a particularly strong effect before planting. While fumigation conferred benefits to yield and NUE, its effects on microbial community structure and function merit further study. [ABSTRACT FROM AUTHOR]

ABSTRACT Streptomyces scabies is a phytopathogen associated with common scab disease. This is mainly attributed to its ability to produce the phytotoxin thaxtomin A, the biosynthesis of which is triggered by cellobiose. During a survey of other metabolites released in the presence of cellobiose, we discovered additional compounds in the thaxtomin-containing extract from Streptomyces scabies. Structural analysis by mass spectrometry (MS) and nuclear magnetic resonance (NMR) revealed that these compounds are amino acid sequence variants of the TOR (target of rapamycin) kinase (TORK) pathway-inhibitory lipopeptide rotihibin A, and the main compounds were named rotihibins C and D. In contrast to thaxtomin, the production of rotihibins C and D was also elicited in the presence of glucose, indicating different regulation of their biosynthesis. Through a combination of shotgun and targeted proteomics, the putative rotihibin biosynthetic gene cluster rth was identified in the publicly available genome of S. scabies 87-22. This cluster spans 33 kbp and encodes 2 different nonribosomal peptide synthetases (NRPSs) and 12 additional enzymes. Homologous rth biosynthetic gene clusters were found in other publicly available and complete actinomycete genomes. Rotihibins C and D display herbicidal activity against Lemna minor and Arabidopsis thaliana at low concentrations, shown by monitoring the effects on growth and the maximal photochemistry efficiency of photosystem II. IMPORTANCE Rotihibins A and B are plant growth inhibitors acting on the TORK pathway. We report the isolation and characterization of new sequence analogues of rotihibin from Streptomyces scabies, a major cause of common scab in potato and other tuber and root vegetables. By combining proteomics data with genomic analysis, we found a cryptic biosynthetic gene cluster coding for enzyme machinery capable of rotihibin production. This work may lead to the biotechnological production of variants of this lipopeptide to investigate the exact mechanism by which it can target the plant TORK pathway in Arabidopsis thaliana. In addition, bioinformatics revealed the existence of other variants in plant-associated Streptomyces strains, both pathogenic and nonpathogenic species, raising new questions about the actual function of this lipopeptide. The discovery of a module in the nonribosomal peptide synthetase (NRPS) that incorporates the unusual citrulline residue may improve the prediction of peptides encoded by cryptic NRPS gene clusters.

Common scab of potato causes important economic losses worldwide following the development of necrotic lesions on tubers. In this study, the genomes of 14 prevalent scab-causing Streptomyces spp. isolated from Prince Edward Island, one of the most important Canadian potato production areas, were sequenced and annotated. Their phylogenomic affiliation was determined, their pan-genome was characterized, and pathogenic determinants involved in their virulence, ranging from weak to aggressive, were compared. 13 out of 14 strains clustered with Streptomyces scabiei, while the last strain clustered with Streptomyces acidiscabies. The toxicogenic and colonization genomic regions were compared, and while some atypical gene organizations were observed, no clear correlation with virulence was observed. The production of the phytotoxin thaxtomin A was also quantified and again, contrary to previous reports in the literature, no clear correlation was found between the amount of thaxtomin A secreted, and the virulence observed. Although no significant differences were observed when comparing the presence/absence of the main virulence factors among the strains of S. scabiei, a distinct profile was observed for S. acidiscabies. Several mutations predicted to affect the functionality of some virulence factors were identified, including one in the bldA gene that correlates with the absence of thaxtomin A production despite the presence of the corresponding biosynthetic gene cluster in S. scabiei LBUM 1485. These novel findings obtained using a large number of scab-causing Streptomyces strains are challenging some assumptions made so far on Streptomyces’ virulence and suggest that other factors, yet to be characterized, are also key contributors.

Potato common scab (CS) is a worldwide soil-borne disease that severely reduces tuber quality and market value. We observed that foliar application of tryptophan (Trp) could induce resistance against CS. However, the mechanism of Trp as an inducer to trigger host immune responses is still unclear. To facilitate dissecting the molecular mechanisms, the transcriptome of foliar application of Trp and water (control, C) was compared under Streptomyces scabies (S) inoculation and uninoculation. Results showed that 4867 differentially expressed genes (DEGs) were identified under S. scabies uninoculation (C-vs-Trp) and 2069 DEGs were identified under S. scabies inoculation (S-vs-S+Trp). Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses indicated that Trp induced resistance related to the metabolic process, response to stimulus, and biological regulation. As phytohormone metabolic pathways related to inducing resistance, the expression patterns of candidate genes involved in salicylic acid (SA) and jasmonic acid/ethylene (JA/ET) pathways were analyzed using qRT-PCR. Their expression patterns showed that the systemic acquired resistance (SAR) and induced systemic resistance (ISR) pathways could be co-induced by Trp under S. scabies uninoculation. However, the SAR pathway was induced by Trp under S. scabies inoculation. This study will provide insights into Trp-induced resistance mechanisms of potato for controlling CS, and extend the application methods of Trp as a plant resistance inducer in a way that is cheap, safe, and environmentally friendly.

Common scab is a soilborne disease that occurs in potato worldwide. Scab is usually present superficially on potato tubers but nonetheless reduces marketability. A genome-wide association study for common scab resistance was performed using 13,002 genome-wide SNPs, with 165 genotypes mostly for chip-processing. We identified a novel QTL for common scab resistance that explained at most 14.7% of the total variance; this QTL was within the 640 kb interval between 0.43 Mb and 1.07 Mb on potato chromosome 1. Recessive homozygosity at this QTL increased levels of resistance. There is no agreement in terms of the locations of QTLs and their genetic modes between the results of previous studies and the present study or among any study. As such, common scab resistance is a highly complex trait, as the QTLs discovered to date are all minor-effect QTLs. [ABSTRACT FROM AUTHOR]

Common scab (CS) is a potato disease that significantly decreases the market value of potato tubers after the development of necrotic lesions on their surface. Streptomyces scabiei is the main causal agent of CS; however, other closely related species, including S. acidiscabies and S. turgidiscabies, have also been shown to cause the disease. In this study, we characterized the genetic and phenotypic diversity of Streptomyces spp. causing CS in Prince Edward Island, the main potato-producing province in Canada. Two hundred and ninety-six pathogenic Streptomyces spp. isolates were retrieved from diseased tubers harvested from six fields located across a longitudinal geographical gradient. Genome fingerprinting analyses using repetitive elements PCR (ERIC- and BOX-PCR) revealed 14 distinct genetic groups. Thirteen groups were taxonomically affiliated with S. scabiei, whereas the fourteenth group was affiliated with S. acidiscabies. Their geographical distribution was characterized and revealed that on average between six and eight different genetic groups were detected per field, with variable abundance. Virulence assays showed strong differences in virulence between the genetic groups, ranging from low to highly virulent. Interestingly, pathogenic Streptomyces spp. populations in each field seem to be dominated by the most virulent genetic groups. The results obtained will contribute to better understanding of the population dynamic of pathogenic Streptomyces spp. causing CS of potato and promoting the development of more efficient detection and intervention tools to manage this important potato disease. [ABSTRACT FROM AUTHOR]

Abstract Background Soil microorganisms can mediate the occurrence of plant diseases. Potato common scab (CS) is a refractory disease caused by pathogenic Streptomyces that occurs worldwide, but little is known about the interactions between CS and the soil microbiome. In this study, four soil-root system compartments (geocaulosphere soil (GS), rhizosphere soil (RS), root-zone soil (ZS), and furrow soil (FS)) were analyzed for potato plants with naturally high (H) and low (L) scab severity levels. We aimed to determine the composition and putative function of the soil microbiome associated with potato CS. Results The copy numbers of the scab phytotoxin biosynthetic gene txtAB and the bacterial 16S rRNA gene as well as the diversity and composition of each of the four soil-root system compartments were examined; GS was the only compartment that exhibited significant differences between the H and L groups. Compared to the H group, the L group exhibited a lower txtAB gene copy number, lower bacterial 16S copy number, higher diversity, higher co-occurrence network complexity, and higher community function similarity within the GS microbiome. The community composition and function of the GS samples were further revealed by shotgun metagenomic sequencing. Variovorax, Stenotrophomonas, and Agrobacterium were the most abundant genera that were significantly and positively correlated with the scab severity level, estimated absolute abundance (EAA) of pathogenic Streptomyces, and txtAB gene copy number. In contrast, Geobacillus, Curtobacterium, and unclassified Geodermatophilaceae were significantly negatively correlated with these three parameters. Compared to the function profiles in the L group, several genes involved in “ABC transporters,” the “bacterial secretion system,” “quorum sensing (QS),” “nitrogen metabolism,” and some metabolism by cytochrome P450 were enriched in the H group. In contrast, some antibiotic biosynthesis pathways were enriched in the L group. Based on the differences in community composition and function, a simple model was proposed to explain the putative relationships between the soil microbiome and CS occurrence. Conclusions The GS microbiome was closely associated with CS severity in the soil-root system, and the occurrence of CS was accompanied by changes in community composition and function. The differential functions provide new clues to elucidate the mechanism underlying the interaction between CS occurrence and the soil microbiome, and varying community compositions provide novel insights into CS occurrence.

Disease resistance is an important characteristic for each variety of potato, and the search for pathogen resistance markers is one of the primary tasks of plant breeding. Higher plants possess a wide spectrum of enzymes catalyzing the hydrolysis of nucleic acids; it is believed that protection against pathogens is the most probable function of the enzymes. RNases are actively involved in several immune systems of higher plants, for example, systemic acquired resistance (SAR) and genetic silencing, hence RNase activity in plant leaves, as a relatively easily measured parameter, can serve as a good marker for the selection of pathogen resistant varieties. We have analyzed sixteen varieties of potatoes permitted for use on the territory of the Russian Federation and tested the correlation of the level of variety­specifc ribonuclease (RNase) activity with such economically valuable traits as maturity and resistance to viruses, late blight and common scab. In general, the level of RNase activity was variety­specifc, which was confrmed by very small values of average squared error for the majority of tested varieties. We have detected a statistically signifcant positive correlation of RNase activity in potato leaves with increased resistance of varieties to phytopathogenic viruses, a negative correlation with resistance to scab and an absence of a signifcant connection with maturity and resistance to late blight, regardless of the organ affected by the oomycete. Thus, the level of RNase activity in potato leaves can be used as a selective marker for resistance to viruses, while varieties with increased RNase activity should be avoided when selecting resistance to scab.

Scab of potato is caused by physiologically distinct species of Streptomyces in different geographic regions of the world. Different strains of this pathogen show considerable variation in their phenotypic and genotypic characteristics. During the current study, disease survey of key potato growing regions of northern India revealed that scab was widely present in potato fields, but in relatively low severity (1-7.9%). Kufri Pukhraj, a widely grown variety of potato in the region, had a mean disease severity of 7.3 per cent, whereas, a less grown variety Lady Rosetta had the highest disease severity (10.5%). One hundred and seven isolates of Streptomyces spp. were categorized into four groups, each having distinct substrate utilization patterns and antibiotic sensitivity. More than 97 per cent of the isolates produced melanin and most of them were pathogenic on potato, whereas, few isolates that did not produce melanoid pigment were non-pathogenic. Multiple antibiotic resistance was observed in the test isolates, with 14 of them tolerating two or more antibiotics. Three of the isolates viz., Strep101, Strep114 & Strep157 could tolerate three antibiotics and three isolates viz., Strep127, Strep154 & Strep178 could tolerate four antibiotics. [ABSTRACT FROM AUTHOR]

Common scab of potato caused by pathogenic Streptomyces species poses an economic burden to commercial potato cultivation. Despite decades of research, no molecular markers linked to this trait are currently available, making the development of scab resistant potato varieties inefficient. We evaluated common scab lesion type and tuber coverage in 198 individuals segregating for common scab resistance in replicated field trials with high natural disease pressure over two growing seasons. To identify genetic features associated with resistance, we genotyped the tetraploid (4x) population and parental lines (Kalkaska and Tundra) using the Illumina Infinium 8303 Potato Array and conducted genome-wide association analysis. Here, we report two significant single nucleotide polymorphism (SNP) markers on chromosome 1 associated with both scab traits in both years as well as a SNP marker on chromosome 2 associated with scab tuber coverage. Gene expression profiling of the parents of this population in response to Thaxtomin A treatment revealed differential expression of genes in tubers putatively involved in cell wall biosynthesis and hormone signaling. [ABSTRACT FROM AUTHOR]

Copyright of Progress in Plant Protection is the property of Institute of Plant Protection and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The outer potato periderm layer consists of dead suberized cells. Suberin, a protective biopolymer, is made of a polyaliphatic portion covalently linked to polyaromatic moieties. Evidence accumulates that Streptomyces scabies, the main causal agent of potato common scab, can degrade the suberin aliphatic part but its ability to degrade the aromatic portion has not been documented. This polyaromatic portion is mainly composed of cinnamic acids. In this study, two cinnamates (trans-ferulic or p-coumaric acids) were added to the culture medium of S. scabies strains EF-35 and 87.22. HPLC quantification revealed that both strains efficiently utilized these compounds. A proteomic study coupled with gene expression analysis led to the identification of putative catabolic pathways for cinnamates. Catabolism of both compounds appeared to occur via the β-ketoadipate pathway. Gene SCAB_15301, encoding for a putative vanillate monooxygenase, was partly deleted from S. scabies strain 87.22 genome. The mutant retained its ability to catabolize trans-ferulic acid into vanillate but lost its ability to further degrade the latter compound. When the wild-type mutant and complemented strains were grown in the presence of suberin-enriched potato periderm, accumulation of vanillic acid was observed only in the mutant culture medium. This work presents evidence that S. scabies can degrade not only the aliphatic part of suberin but also the constituents of suberin aromatic portion. This may provide ecological and pathological advantages to S. scabies as a saprophyte and pathogen.

Potato (Solanum tuberosum) is a staple food crop and is considered one of the main sources of carbohydrates worldwide. Late blight (Phytophthora infestans) and common scab (Streptomyces scabies) are two of the primary production constraints faced by potato farming. Previous studies have identified a few resistance genes for both late blight and common scab; however, these genes explain only a limited fraction of the heritability of these diseases. Genomic selection has been demonstrated to be an effective methodology for breeding value prediction in many major crops (e.g., maize and wheat). However, the technology has received little attention in potato breeding. We present the first genomic selection study involving late blight and common scab in tetraploid potato. Our data involves 4,110 (Single Nucleotide Polymorphisms, SNPs) and phenotypic field evaluations for late blight (n=1,763) and common scab (n=3,885) collected in seven and nine years, respectively. We report moderately high genomic heritability estimates (0.46 ± 0.04 and 0.45 ± 0.017, for late blight and common scab, respectively). The extent of genotype-by-year interaction was high for late blight and low for common scab. Our assessment of prediction accuracy demonstrates the applicability of genomic prediction for tetraploid potato breeding. For both traits, we found that more than 90% of the genetic variance could be captured with an additive model. For common scab, the highest prediction accuracy was achieved using an additive model. For late blight, small but statistically significant gains in prediction accuracy were achieved using a model that accounted for both additive and dominance effects. Using whole-genome regression models we identified SNPs located in previously reported hotspots regions for late blight, on genes associated with systemic disease resistance responses, and a new locus located in a WRKY transcription factor for common scab.

The purpose of the three–year–long field experiment was to identify the effect of the UGmax soil fertilizer (microbiological preparation) on the presence of Streptomyces scabies on tubers of two edible potato cultivars. The experiment was established using the randomized split-block method, in three replications, in the vicinity of central Poland (52°03'N; 22°3'E), on soil consisting of loamy sands, slightly acidic and acidic. The examined factors included: 1st factor: edible potato cultivars (Satina and Typhoon), 2nd factor: doses and dates of application of the UGmax soil fertilizer (1. control object without UGmax; 2. UGmax applied to soil before planting tubers at a dose of 1.0 dm3∙ha-1; 3. UGmax applied to soil before planting tubers at a dose of 0.5 dm3∙ha-1, when the height of plants is about 10–15 cm, and in the flower buds making phase at a dose of 0.25 dm3∙ha-1; 4. UGmax before planting tubers at a dose of 1.0 dm3∙ha-1 and when the height of plants is about 10–15 cm, and in the flower buds making phase at a dose of 0.5 dm3∙ha-1; 5. UGmax when the height of plants is about 10–15 cm, and in the flower buds making phase at a dose of 0.5 dm3∙ha-1). Symptoms of common scab were assessed on a 9–point scale on 100 tubers randomly collected from different experiment objects. As a result of the study, it was demonstrated that treatments with the use of the UGmax soil fertilizer limited the occurrence of common scab on potato tubers and affected the average level of infestation of the sample and the average level of infestation of infested tubers.

Thaxtomin A (TA) is a phytotoxin secreted by Streptomyces scabies that causes common scab in potatoes. However, the mechanism of potato proteomic changes in response to TA is barely known. In this study, the proteomic changes in potato leaves treated with TA were determined using the Isobaric Tags for Relative and Absolute Quantitation (iTRAQ) technique. A total of 693 proteins were considered as differentially expressed proteins (DEPs) following a comparison of leaves treated with TA and sterile water (as a control). Among the identified DEPs, 460 and 233 were upregulated and downregulated, respectively. Based on Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, many DEPs were found to be involved in defense and stress responses. Most DEPs were grouped in carbohydrate metabolism, amino acid metabolism, energy metabolism, and secondary metabolism including oxidation–reduction process, response to stress, plant–pathogen interaction, and plant hormone signal transduction. In this study, we analyzed the changes in proteins to elucidate the mechanism of potato response to TA, and we provided a molecular basis to further study the interaction between plant and TA. These results also offer the option for potato breeding through analysis of the resistant common scab.

Copyright of Progress in Plant Protection is the property of Institute of Plant Protection and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, we aimed at assessing the best conditions for the isolation of actinobacteria from old potato samples. A set of media and pretreatments were tested. The optimal were chosen for the isolation of actinobacteria from potatoes from Peru, Chile and Argentina. Isolates were tested on the presence of thaxtomin phytotoxin by amplification of the respective gene. Phylogenetic position of strains was compared with their geographical origin, pathogenic potential and existence of common scab (CS) symptoms on potato sample. We demonstrated that RNAlater can be successfully used for the long-term preservation of potato peel for subsequent isolation of actinobacteria on R2A medium. Many streptomycetes were thaxtomin-positive, though they are distantly-related to described pathogens causing CS. Genus Nocardia was first reported to be thaxtomin-positive. Potentially pathogenic strains were isolated not only from infected potato but also from those lacking CS symptoms. Some strains from scabby potatoes were thaxtomin-negative. [ABSTRACT FROM AUTHOR]

The outer potato periderm layer consists of dead suberized cells. Suberin, a protective biopolymer, is made of a polyaliphatic portion covalently linked to polyaromatic moieties. Evidence accumulates that Streptomyces scabies , the main causal agent of potato common scab, can degrade the suberin aliphatic part but its ability to degrade the aromatic portion has not been documented. This polyaromatic portion is mainly composed of cinnamic acids. In this study, two cinnamates (trans -ferulic or p -coumaric acids) were added to the culture medium of S. scabies strains EF-35 and 87.22. HPLC quantification revealed that both strains efficiently utilized these compounds. A proteomic study coupled with gene expression analysis led to the identification of putative catabolic pathways for cinnamates. Catabolism of both compounds appeared to occur via the β-ketoadipate pathway. Gene SCAB_15301, encoding for a putative vanillate monooxygenase, was partly deleted from S. scabies strain 87.22 genome. The mutant retained its ability to catabolize trans -ferulic acid into vanillate but lost its ability to further degrade the latter compound. When the wild-type mutant and complemented strains were grown in the presence of suberin-enriched potato periderm, accumulation of vanillic acid was observed only in the mutant culture medium. This work presents evidence that S. scabies can degrade not only the aliphatic part of suberin but also the constituents of suberin aromatic portion. This may provide ecological and pathological advantages to S. scabies as a saprophyte and pathogen. [ABSTRACT FROM AUTHOR]

[ Objective]The changes of physiological characteristics of different resistant potato varieties inoculated with potato common seal) bacteria were studied to provide theoretical basis for rapid screening and cultivation of resistant potato varieties. [ Method]The physiological and biochemical indexes of potato common seal) resistance were determined, and the activities of peroxidase (POD) , superoxide dismutase (SOD) , polyphenol oxidase ( PPO) ,malondialdehyde in resistant and susceptible potato treated with potato common scab were analyzed. [ Result]The results showed that the contents of POD, SOD and PPO were increased after potato tubers were inoculated with potato common scab. Among them, the activity of disease-resistant varieties POD PPO after inoculation was significantly higher than that of susceptible varieties. SOD activity of potato tubers was decreased, increased and then decreased after potato common scab infection, and the enzyme content of susceptible cultivars was higher than that of resistant eultivars. Inoculation of scab promoted the increase of MDA content in susceptible eultivars, and MDA content in susceptible cultivars was always higher than that in resistant cultivars. [ Conclusion] POD, SOD, PPO increased in different degree in tubers inoculated with common scab, but the activity of PAL did not change after inoculation. POD activity and PPO activity in tuber of resistant cultivars remained at a high level before and after inoculation, while the activity of POD activity PPO in tuber of susceptible cultivars was relatively low, indicating that POD activity and PPO activity in tuber played an active role in resisting scab infection of potato varieties. SOD activity of susceptible cultivars was significantly higher than that of resistant cultivars before and after inoculation. Resistant cultivars showed a trend of decreasing first and then increasing after inoculation. After inoculated with different resistant potato tubers, MDA content in susceptible varieties increased, and that of susceptible varieties was higher than that of resistant varieties, indicating that cells and biofilm of susceptible varieties were destroyed more seriously. In con elusion, POD activity, PPO activity, SOD activity, soluble sugar content, MDA content may be used as auxiliary means of the resistance i dentification for potato to common seal). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Antimicrobial potential of Controller, Impose, Phostrol, Ridomil Gold plus and Roxyl Plus was determined for Pectobacterium atrosepticum and Streptomyces scabies. The cidal effect against P. atrosepticum was only shown by the fungicide Controller. S. scabies was highly affected by Controller, Impose and Roxyl plus compared to RidomilGold plus and Phostrol that did not inhibit the growth. The MIC of Controller was found to be 4000 ppm for P. atrosepticum and S. scabies. On the other hand, the MICs of Impose and Roxyl Plus were found to be 4000 ppm and 3000 ppm respectively for S. scabies. Application of Controller against blackleg significantly decreased the incidence of the disease in potted potato plants. Application of Controller, Impose and Roxyl Plus at 3.0g/I to control common scab significantly decreased the disease. Conclusive results were obtained by the 4.0 g/I application. Residues of ingredients of these fungicides in potato tuber 60 day after application were below the approved maximum residue level (MRL). [ABSTRACT FROM AUTHOR]