Scab Development Research Articles

Role of previous crops and mineral fertilizers in pathogenesis of potato black scab and crop productivity

One of the main factors limiting the potato yield in Western Siberia is various crop diseases, among which soil and tuber infections hold a special place. The sore issue in potatoes production is black scab. The economic significance of this disease is estimated at 50 % yield loss during the growing season. The results of analyzing the effect of previous crops (potatoes, oats and tendergreen) and mineral fertilizers (N40P40K80) on pathogenesis of black scab in potato plantations, and also crop productivity are presented in the paper. Evaluation of the used techniques effect on development of black scab was performed on natural backgrounds in conditions of forest-steppe zone of Priobye in the Novosibirsk region. The seasonal dynamics of the Rhizoctonia solani fungus in the soil has a characteristic increase in the number at the end of plants growing season. In the conditions of Western Siberia, in the course of pathological process of black scab, the soil infection (proportion of the factor effect from 50 % during the phase of full germination to 90 % to the flowering phase) plays the most important role. Oats and tendergreen had been affecting on the agent of black scab disease during two years after cultivation as a precursor, and oats affected the pathogen more strongly in the second year of potato cultivation. On average according to factors, oats and tendergreen with mineral fertilizers (N40P40K80) reliably reduce development of black scab on plants 1.1-1.3 times as compared to potatoes cultivated in monoculture, and mineral fertilizers significantly (1.3 times) increase the plants performance. The predecessors (on average) had practically no effect on this indicator. The yield of potatoes in monoculture and after oats is almost the same, and after tendergreen it is insignificantly higher (1.1 times). Mastering environmentally friendly technologies for protecting potatoes from soil and tuber infections and implementation of those into production will contribute to obtaining stable crops of a high quality culture, and, as a result, formation of efficient agro-industrial complex ensuring the country’s food security.

Influence of plant immunity inducers on the degree of apple scab development when applied in plant protection systems in the zone of humid subtropics of Abkhazia

One of the ways to reduce pesticide load and prevent emergence of pathogen resistance can be the use of plant immunity inducers in plant protection systems. The purpose of these studies was to evaluate an efficiency of natural plant immunity inducers Albit® (poly-beta-hydroxybutyric acid), Immunocytophite® (arachidonic acid ethyl ether) and Ecogel® (chitosan lactate) in apple scab protection systems in Abkhazia. The maximum resistance of apple trees to this phytopathogen was recorded in the experimental variants with Albit® and Ecogel® application in half dosages of fungicides and in the variant of production processing (biological efficiency reached 79.4 %). Plant immunity inducers used on apple trees showed cultivar-specificity. For the four-year research period, the greatest efficiency of immunity inducers was achieved on the susceptible cultivar Idared in the second year of the experiment, while on the relatively scab-resistant cultivar Golden Rangers – it was achieved only in the third year. The greatest stability in the efficiency for a four-year period was observed for the tank mix Albit with half dosages of fungicides. Immunocytophyte® was characterized by lower inducing activity, which is associated with its activation of the jasmonate pathway for the formation of non-specific induced immunity.

СИСТЕМЫ ЗАЩИТЫ ЯБЛОНЕВОГО САДА ОТ БОЛЕЗНЕЙ И ВРЕДИТЕЛЕЙ

Weather conditions influenced the level of scab development and fruit damage by codling moth in 2017-2018. Significant changes in the daily air temperature during the growing season, long periods of low temperatures in May and early June, and frosts during blossoming were registered in 2017. There were the main reasons of plant weakening and increasing the development of scab. Weather conditions of the growing season in 2018 were characterized by uneven precipitation and excess of the average daily air temperature, which caused the development of codling moth. In the standard, the development of scab on leaves and fruits amounted to 47.0% and 29.1 % in 2017, and 9.8 % and 3.5 % in 2018. The fruit damage by codling moth in the standard in 2017 was 18.5 % and in 2018 — 50.9 %. Application of the experimental system of fungicides against scab (Indigo, KS; Cantor, KKR; Medea, ME; Grenni, CS) and tank mixture (Strobi, VDG + Grenni, CS) provided the biological efficiency on leaves and fruits of 91.9 % и 90.3 % (2017), 90.4 % и 91.4 % (2018), respectively. The application of plant protection products Gerold, VSK, Calypso, KS and Junona, ME against codling moth in experimental system provided the biological efficiency of 98.4 % (2017) and 94.7 % (2018).

Plant Protection And Foliar Fertilizing Technology Of Apple (Malus Domestica Borkh)

The systematic use of foliar fertilizers during growing season is a relatively new agronomic practice in Central Russia and it is still not widely used in horticultural enterprises of the region. One of the main reasons for this is the relatively high cost of this method. Producers prefer soil fertilization which adversely affect the environment. A significant reduction in cost of foliar fertilizing could be obtained by combining foliar nutrition with plant protection. The number of plant protection treatments, as well as toxicity of some products, is increasing annually. The use of fertilizers and plant protection products negatively affect the environment. It is very important to find ways of decreasing this load on surroundings. Currently, many different biological preparations for plant protection exist which are suggested to replace chemicals. The problem is in their relative low effectiveness compared to traditional plant protection products. The authors have studied the most popular plant protection products (in a traditional protection system) and application of foliar fertilizers (in a mineral foliar fertilizer system) in comparison with ecologized plant protection system (based on bacterial and low-toxic preparations) in tank mixtures with seaweed extracts-based foliar fertilizers. The authors have considered yield, scab development, content of calcium in leaves and fruits as the main criteria of this study. The research was carried out in the irrigated orchard (1,480 trees/ha), planted in leached meadow-chernozem soil. The investigation was carried out in 2013-2015. The results of traditional plant protection system in tank mixtures with mineral foliar fertilizer application, as well as ecologized products with seaweed extracts-based preparations, have been compared. Traditional plant protection system in combination with mineral foliar fertilizers have ensured a higher content of calcium in leaves and fruits, less damage from scab and higher yields. We can consider two ways of replacing traditional plant protection and fertilizing approach: the development of new highly efficient ecologized products or increased financial support.

Cultivar Resistance to Common Scab Disease of Potato Is Dependent on the Pathogen Species.

Common scab of potato is a superficial tuber disease caused by Streptomyces species that produce the phytotoxin thaxtomin. Because common scab development is highly dependent on the effects of this single toxin, the current operating paradigm in common scab pathology is that a potato cultivar resistant to one strain of the common scab pathogen is resistant to all strains. However, cultivar resistance to common scab disease identified in one breeding program is often not durable when tested in other potato breeding programs across the United States. We infected 55 potato cultivar populations with three distinct species of the common scab pathogen and identified cultivars that were resistant or susceptible to all three species and cultivars that had widely varying resistance dependent on the pathogen species. Overall lower virulence was associated with the strain that produces the least thaxtomin. This result showcases several cultivars of potato that are expected to be resistant to the majority of common scab populations but also highlights that many potato cultivars are resistant to only specific species of the pathogen. These results demonstrate that extension specialists and growers must consider their local population of the common scab pathogen when selecting which cultivars to plant for common scab resistance.

Test of fungicide Farmaiod, GS for apple tree viral diseases control

In the Krasnodar Territory, on the Renet Simirenko apple variety, symptoms corresponding to the manifestation of viral diseases were found: chlorotic leaf spot, dark green depressed spots on the fruit, which manifest themselves at the end of ripening before harvesting and during storage. Identification of pathogens was performed by Enzyme Immunoassay (ELISA). Samples were tested for the presence of apple chlorotic leaf spot virus (ACLSV), apple stem pitting virus (ASPV), apple stem grooving virus (ASGV), and apple mosaic virus (ApMV). As a result of the analysis, viruses of chlorotic leaf spot of the apple tree (ACLSV) and pitted of apple tree wood (ASPV) were detected. To protect the apple tree from viruses, the drug Farmaiod, GS, whose active ingredient is iodine, was tested. The first treatment was carried out during the 2014 leaf fall period with a consumption rate of 1.0 l/ha and continued in the following 2015 in the phenophase "green cap" and "fruit diameter 10-20 mm" in two versions with consumption rates of 0.5 and 1,0 l/ha. With the onset of leaf fall in the same areas, the treatment cycle was repeated according to the same scheme. Accounting was carried out by the method of visual diagnostics, in addition, at the end of the first and second seasons, virological analyzes were performed by ELISA. As a result of research, it was noted that 3-fold use of the drug Farmaiod, GS in apple trees of the variety Renet Simirenko restrained the development of the apple tree acle virus (ASPV) and completely suppressed the apple leaf chlorophyll virus (ACLSV). The weather conditions of 2016 test triggered a strong manifestation of scab on leaves and fruits. In the experimental variants, it was noted that the drug at 78.3-83.1 % inhibits the development of apple scab. Treatment with Farmaiod, GS also fostered harvest increase and premium output. The maximum results regarding restraints of infectious processes as well as harvest increase were received when applying the preparation with consumption rate of 1,0 l/ha.

MUTU BUAH JERUK KALAMANSI PADA BERBAGAI TINGKAT SERANGAN PENYAKIT KUDIS

[FRUIT QUALITIES OF CALAMANSI UNDER DIFFERENT SCAB DISEASE SEVERITIES]. Citrus scab caused by Elsinoe fawcettii dan Elsinoe australis fungi is an important disease for calamansi lime. The pathogen can result creamy-yellowish, raised, rounded, corky scabs appear on the rind surface of the fruit that reduces marketabilityof the fruit. The objective of this study was to evaluate the development and intensity of scab and their effects on the physical and chemical qualities of calamansi fruits. The observations were made on 30 fruit samples collected from farmer’s calamansi orchard for the development and intensity of disease symptoms, fruit appearances, juice content, and total soluble solids of the juice. The results showed that the pathogen began to attack on early fruit set phase. The intensity of the disease at the beginning of the observation was 11.06% and increased to 58.18% with an average rate of attack intensity of 14.54%. The disease reduced the fruit weight, fruit diameter, juice volume and total soluble solid levels.

МОНИТОРИНГ РАЗВИТИЯ ПАРШИ ЯБЛОНИ (VENTURIA INAEQUALIS (COOKE) G. WINTER) В САДУ НАУЧНО-ИССЛЕДОВАТЕЛЬСКОГО ИНСТИТУТА «ЖИГУЛЕВСКИЕ САДЫ»

Studies conducted in perennial plantations of fruit crops of the Research Institute “Zhiguliy Gardens” in 2015-2018 showed that the main disease in the apple orchard is the scab Venturia inaqualis (Cooke) G. Winter. The variety most susceptible to this pathogen is the apple variety Spartak. Weather conditions in 2015, 2016 and 2017 favored the development of scab epiphytotics. Monitoring of the scab development dynamics taking into account the weather conditions made it possible to change the plant protection scheme in a timely manner and achieve a positive dynamics of reducing the development of scab on leaves and fruits in 2018 and reduce the stock of the pathogen for 2019.

Working collection formation of apple-tree (Malus domestica Mill.) gene pool for priority breeding trends

Aim. To define the priority trends of apple breeding in the southern steppe of Ukraine and to identify varieties – sources of high valuable-for-breeding indices for building up a working collection. Results and Discussion. Spring frosts and wet weather in May-June contributing to development of the scab pathogen (Venturia inaequalis), high temperature and water deficit in the 2nd half of the growing period, when fruits grow and ripen, are the major stress weather/climatic factors for apple trees in the southern steppe of Ukraine. Therefore, the priority in breeding is given to developing varieties that would be resistant to several unfavorable factors. At the same time, commercial use of new varieties is possible provided high commercial quality indicators of fruits. High resistance of buds to spring frosts was observed in varieties Vechirnia Zoria, Moldavskoye Krasnoye, and Prima. Oligogenic varieties (genes Vm and Vf), including Harant, Skifske Zoloto, and Liberty, showed no signs of scab development. Varieties with polygenic resistance to this disease were identified; they included Vechirnia Zoria, Ornament, Carola. Drought-tolerant varieties with high water-holding capacity of leaves and their turgor restoration after wilting, including Carola, Florina, and Prima, were selected by a laboratory method. Assessment of drought tolerance in the field made it possible to enrich this group with numerous varieties. Varieties giving fruits with high commercial qualities on insufficient water availability, such as Vechirnia Zoria, Harant, Moldavskoye Krasnoye, Ornament and others, were distinguished. Varieties combining resistance to several unfavorable abiotic and biotic factors with high marketability traits of fruits were singled out. Among them. Harant, Delicious Spur, Liberty, and Prima should be mentioned. Conclusions. The development of varieties with complex tolerance to spring frosts, drought, scab pathogen and high qualities of fruits is the priority trend in the breeding of apple trees in the southern steppe of Ukraine. Varieties - sources of individual valuable traits and their various combinations were identified. Varieties Vechirnia Zoria, Moldavskoye Krasnoye, Ornament, and Golden Resistant combine the maximum number of valuable-for-breeding features. It is varieties-sources of several traits that should make up a working collection of apple trees to increase the breeding efficiency.

Развитие парши яблони и эффективность систем защиты в борьбе с ней

Развитие парши яблони и эффективность систем защиты в борьбе с ней

A new interspecific pear cultivar Yutaka: highly resistant to the two major diseases scab and black spot on Asian pears

Scab, caused by Venturia nashicola, is the most important disease of Asian pears. In Japan, the most popular and widely grown pear cultivar (cv.) Kousui is resistant to black spot, caused by the Japanese pear pathotype of Alternaria alternata, but highly susceptible to scab. Recently, a new interspecific pear cv. Yutaka carrying high fruit quality was registered officially after a cross between the Chinese pear cv. Hongli and the Japanese pear cv. Housui. Accordingly, tests were conducted to assess resistance of cv. Yutaka to scab, black spot and anthracnose. When conidial suspensions of V. nashicola were spray inoculated onto potted trees, leaves of cv. Yutaka showed no disease symptoms although severe scab development was recorded on the susceptible reference cv. Kousui. Furthermore, neither black spot symptoms nor necrosis formation were observed when leaves of cv. Yutaka were inoculated with conidial suspensions of the A. alternata Japanese pear pathotype or treated with a culture filtrate containing the host-specific AK-toxin of this pathogen, respectively. These results strongly indicate that cv. Yutaka is highly resistant to scab and black spot. Inoculation tests also suggested the potential high levels of resistance of cv. Yutaka to anthracnose caused by Colletotrichum gloeosporioides sensu lato. The introduction of this new pear cultivar will reduce fungicide applications in pear orchards and thus lower the risk of fungicide resistance development in these pathogens.

Protection of potato against scab

The results of studies to determine the effectiveness of chemical and biological preparations for potato scab development are presented. Their positive influence on potato yield is shown. It has been established that the use of fungicides and biologics for the presowing treatment of tubers, somewhat limits the development of ordinary scab. The highest efficiency for two years of observations was noted with the use of fungicides Rovral Aquaflo 500 and Serkadis.

Effect of Sulphur and Irrigation Regimes on Potato Common Scab Development in Khartoum Area

Effect of Sulphur and Irrigation Regimes on Potato Common Scab Development in Khartoum Area

Validation of a mechanistic model for predicting fruit scab infection on different loquat cultivars

Scab, caused by Fusicladium eriobotryae , is the main disease affecting loquat ( Eriobotrya japonica ) in the Mediterranean basin. A mechanistic epidemiological model developed in Spain to predict infection of loquat fruit by conidia was assessed in the main loquat cultivated area of Italy (Sicily). A 3-year study (2014–2016) was carried out in an experimental orchard on three loquat cultivars: Algerie, Peluche and San Filipparo. For each cultivar, output of the model was compared with observed scab development on fruits. The scab epidemics observed were different in different years and cultivars, representing a suitable data set for model validation. The model correctly predicted loquat scab, as demonstrated by the goodness of fit between model predictions and observed disease incidence on fruits ( R 2 > 0.85), confirming the accuracy and robustness of the model for predicting scab development in loquat orchards. The use of the model for fungicide scheduling against F. eriobotryae may improve the management of loquat scab by reducing the number of required fungicide applications.

Chloropicrin Soil Fumigation Reduces Spongospora subterranea Soil Inoculum Levels but Does Not Control Powdery Scab Disease on Roots and Tubers of Potato

The effect of chloropicrin fumigation on the soil populations of Spongospora subterranea and the development of powdery scab, formation of root galls and tuber yield was investigated in seven field trials conducted in Minnesota and North Dakota. Sixteen potato cultivars, with different levels of susceptibility to disease on roots and tubers, were planted in plots treated with chloropicrin at rates ranging from zero to 201.8 kg a.i. ha−1. The amount of S. subterranea DNA in soil was determined using qPCR. Bioassays were conducted to further assess the effect of chloropicrin fumigation on root colonization by S. subterranea in two potato cultivars with contrasting disease susceptibility. In the field, chloropicrin applied at rates between 70.1 to 201.8 kg a.i. ha−1 significantly decreased S. subterranea initial inoculum in soil but increased the amount of disease observed on roots and tubers of susceptible cultivars. The effect of increasing disease was confirmed in controlled conditions experiments. Although the amount of S. subterranea DNA in roots of bioassay plants increased with increasing chloropicrin rates, it remained similar among potato cultivars. Chloropicrin fumigation significantly increased tuber yield which in cultivars such as Shepody and Umatilla Russet were associated with the amount root galls (r = 0.30; P < 0.03). Results of these studies contradict earlier reports on the use of chloropicrin fumigation for the control of powdery scab. Factors other than inoculum level, such as environmental conditions that affect inoculum efficiency and host susceptibility, may be significant contributors to the development of powdery scab and root gall formation.

Measures to Prevent and Combat Pear Scab (Venturia pirina) in the Climate Conditions of Lapusel

In this paper we studied the emergence and development of pear scab (Venturia pirina), as well as the combat methods, testing a couple of fungicides. The aim of the research has been to highlight the resistance, respectively the sensitivity of some pear varieties against the fungi attack, in order to make recommendations for the new plantations, as well as the testing of 7 fungicides, remarking the product with the highest biological effectiveness. The researches were conducted in the years 2013-2014 at the company SC Mecanochim Lapusel, Maramures County. The experiments were conducted on plots planted with the Olivier de Serres and Bergamotte Crassane varieties. The attack was calculated determining the attack frequency, intensity and degree. The linear-interrupted method was used, comprising 3 variants of 5 trees each. Analyzing the climate data, it has resulted that in 2013 scab had favourable development and attack conditions. The Olivier de Serres variety was noted for its resistance to fungus attack, with a frequency of 0.2-1.3% on fruits and insignificant frequency on leaves, for all 7 tested product variants. The Bergamotte Crassane variety was placed on the other end, with a higher frequency and intensity, both on fruits (2-3%) and on leaves (2.5-3.5%). The infections diminished in 2014 due to the unfavourable climatic conditions. Three products had better results, from the seven tested products, thus: Alcupral 50PU, Stroby DF and Chorus 50 WG.

Differentiation in populations of the apple scab fungusVenturia inaequalison cultivars in a mixed orchard remain over time

The ascomyceteVenturia inaequaliscauses annual epidemics of apple scab worldwide. Scab development is reduced in mixed cultivar orchards compared with monocultures. In order to use mixtures in commercial production, how the population of scab changes in a mixed orchard needs to be understood, together with how likely a super race, with virulence factors overcoming multiple resistance factors in the mixed orchard, is to emerge and become dominant. This study used simple sequence repeat (SSR) markers to investigate the temporal change of scab populations in two mixed cultivar orchards in theUKto infer the likelihood of emergence of a scab super race. There were no significant differences between the populations at the two sampling times (6 or 7 years apart) in either of the two mixed orchards. In one of the orchards, apple scab populations on different cultivars were significantly different and the differences did not diminish over time. These results suggest that it is not inevitable that a super race ofV. inaequaliswill become dominant during the lifetime of a commercial apple orchard.

Pseudomonas fluorescens LBUM223 Increases Potato Yield and Reduces Common Scab Symptoms in the Field.

Common scab of potato, caused by pathogenic Streptomyces spp., is an important disease not efficiently controlled by current methods. We previously demonstrated that Pseudomonas fluorescens LBUM223 reduces common scab development under controlled conditions through phenazine-1-carboxylic (PCA) production, leading to reduced thaxtomin A production by the pathogen, a key pathogenicity and virulence factor. Here, we aimed at determining if LBUM223 is able to increase potato yield and control common scab under field conditions, while characterizing the biocontrol mechanisms involved. We investigated if a reduction in pathogen soil populations, activation of induced systemic resistance in potato, and/or changes in txtA gene expression, involved in thaxtomin A biosynthesis in pathogenic Streptomyces spp. were involved in common scab control by LBUM223. Common scab symptoms were significantly reduced and total tuber weight increased by 46% using biweekly applications of LBUM223. LBUM223 did not reduce pathogen soil populations, nor was potato systemic defense-related gene expression significantly altered between treatments. However, a significant down-regulation of txtA expression occurred in the geocaulosphere. This is the first demonstration that a Pseudomonas strain can directly alter the transcriptional activity of a key pathogenesis gene in a plant pathogen under field conditions, contributing to disease control.

Toward an Integrated Use of Biological Control by Cladosporium cladosporioides H39 in Apple Scab (Venturia inaequalis) Management.

Apple scab, caused by Venturia inaequalis, is the most important disease in apple production, reducing yield and quality of fruit. Control of apple scab in commercial orchards currently depends on multiple applications of fungicides. The potential of the antagonistic isolate Cladosporium cladosporioides H39, originating from a sporulating colony of V. inaequalis, to control apple scab development was tested in eight trials during 2 years in orchards in Eperjeske (Hungary), Dabrowice (Poland), and Bavendorf (Germany) planted with different cultivars. Treatments were conducted as calendar sprays or after infection periods. Additional trials in an orchard in Randwijk (The Netherlands) focused on the effect of timing of antagonist application before or after infection periods. The overall results of the field trials consistently showed-for the first time-that stand-alone applications of the antagonist C. cladosporioides H39 can reduce apple scab in leaves and fruit. This was demonstrated in an organic growing system as well as in conventional orchards by spray schedules applied during the primary or the summer season. In both systems, the same control levels could be reached as with common fungicide schedules. Efficacies reached 42 to 98% on leaf scab incidence and 41 to 94% on fruit scab. The antagonist was also effective if applied one or even several days (equivalent to approximately 300 to 2,000 degree h) after infection events in several field trials and a trial conducted in Randwijk with single-spray applications at different intervals before or after infection events. Better understanding of the biology of the antagonist will help to further exploit its use in apple scab control.

High soil moisture reduces common scab caused by Streptomyces turgidiscabies and Streptomyces europaeiscabiei in potato

Common scab (Streptomyces spp.) is a worldwide economic important disease of potato (Solanum tuberosum L.) because it degrades the appearance of the tubers and thereby decreases market value. For the newly reported Streptomyces turgidiscabies and Streptomyces europaeiscabiei in Norway, little is known about their specific environmental requirements, particularly their pathogenicity under varying moisture levels. Scab development after soil inoculation of S. turgidiscabies and S. europaeiscabiei in dry, normal and wet soils was studied in three pot experiments (2009–2011) under controlled climate conditions at natural light in Tromsø, Norway (69.7 N). With increased soil moisture, statistical significant reductions in scab severity were found in two out of three experiments for S. turgidiscabies (about 50% reduction). Similarly, scab caused by S. europaeiscabiei was reduced significantly in one experiment (65% reduction), and with a tendency of reduction in the other experiments. Scab development from seed-transmitted inoculum was investigated for both species. In one trial with four scab severity levels on mother tubers (0%, 10%, 30% and 50% of surface covered), we found that seed-transmitted disease development occurred for both species although few lesions were recorded. There were no significant differences in scab severity on progeny tubers, no matter the infection levels on seed tubers. These results indicate that seed tubers might play a minor role for transmitting common scab for S. turgidiscabies and S. europaeiscabiei, but further work is warranted. Related to growers practice, the results implicate that potato common scab caused by S. europaeiscabiei and S. turgidiscabies may be reduced by irrigation during the early stages of tuber formation, similar to currently recommended control measures for Streptomyces scabies.