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1.
M. Bengtsson E. Wulff H. J. Lyngs Jørgensen A. Pham M. Lübeck J. Hockenhull 《European journal of plant pathology / European Foundation for Plant Pathology》2009,124(2):187-198
The effect of an extract of Yucca schidigera on the control and infection process of the apple scab pathogen, Venturia inaequalis, was examined and compared with the chemical resistance inducer, acibenzolar-S-methyl (ASM). In seedling assays, both materials significantly reduced apple scab symptoms and pathogen sporulation on leaves
and both showed similar control efficacies as the reference treatment, sulphur. Whereas yucca extract and sulphur gave significant
inhibition of conidial germination in vitro, ASM did not inhibit germination. Histopathological studies of the infection process of V. inaequalis in apple leaves showed that the yucca extract primarily acted by inhibiting pre-penetration events and penetration itself.
In contrast, the ASM treatment significantly inhibited more stages of the infection process (pre-penetration, penetration
and post-penetration events). These observations suggest that the yucca extract acted mainly by a direct fungitoxic effect
whereas ASM, as expected, acted as a resistance inducer. However, expression studies of two genes encoding the PR proteins,
PR1 and PR8, in apple seedlings indicated that yucca extract may also affect plant defence as expression of both genes was
up-regulated following yucca treatment, to a level similar to that observed after treatment with ASM. The fungitoxic effect
of sulphur on V. inaequalis was also confirmed in this study. 相似文献
2.
A 2-year study was conducted to determine the widespread occurrence of overwintered conidial inoculum of Venturia inaequalis and its impact on the apple scab control in 18 apple orchards (organic and integrated) with various levels of scab in the Netherlands. Autumn assessments of scab lesions showed that the integrated orchards had a significantly lower scab incidence (<20%) compared to that of the organic orchards (>60%). At the bud-break phenological stage, the mean numbers of nonviable and viable conidia on 1 cm pieces of shoots ranged from 1 to about 90 and from 6 to more than 1000 in the integrated and the organic orchards, respectively, for both years. However, viable conidia on shoots were found only in 2 integrated and 6 organic orchards out of the 18 and the viability of conidia was below 2%. The mean numbers of viable and nonviable conidia per 100 buds ranged from 24 to more than 1000 and from 230 to almost 5000 in the integrated and the organic orchards, respectively, for both years. In both years, some 60–85% of the conidia was found on the outer bud scales. The percentage viability associated with the outer bud tissues was below 2% for all the orchards. However, the percentage of viable conidia within the inner bud tissues ranged from 0% to 6% in the integrated and from 2% to 11% in the organic orchards for both years. Differences between the organic and the integrated orchards were clearly demonstrated for overwintered conidia associated with both shoot and bud samples. The relationship between autumn scab incidence and numbers of overwintered conidia associated with shoots or buds was exponential. If the autumn scab incidence was above 40%, then the number of overwintered conidia markedly increased. We conclude that specific treatments for overwintering conidia of Venturia inaequalis may not be necessary in integrated orchards with a low scab incidence in the previous autumn. However, the risk of early scab epidemics initiated by overwintered conidia potentially is high in organic orchards. Preventative measures in early spring and also in the previous year must be established in these orchards. 相似文献
3.
A new class of agricultural fungicides derived from strobilurins act as respiration inhibitors by binding to mitochondrial cytochrome b. The effects of the strobilurin, kresoxim-methyl, on conidia germination, mycelial growth and the protection of apple leaves from scab development were investigated for two isolates of Venturia inaequalis randomly selected from a culture collection. Inhibition of mycelial growth required relatively high doses of kresoxim-methyl (ED50=1 μg ml-1) for both isolates. In comparison, germination of conidia was highly sensitive for one of the isolates (ED50=0·005 μg ml-1), while the level of inhibition achieved for the second isolate was 60-fold less (ED50=0·3 μg ml-1). As deduced from identical sequences of cytochrome b cDNAs prepared from both isolates, the different responses of germinating conidia to kresoxim-methyl were not caused by differences in the sequence of cytochrome b as the target site for strobilurin action. Strong synergistic effects of salicylhydroxamic acid on kresoxim-methyl inhibitory potency suggested that the reduced kresoxim-methyl sensitivity observed for germinating conidia was caused by interference of the alternative respiratory pathway with inhibitor action. However, this mechanism of target site circumvention in germinating conidia had no adverse effects on the protection of apple leaves from scab infection by kresoxim-methyl. © 1998 Society of Chemical Industry 相似文献
4.
Achim E. Gau Mostafa Koutb Markus Piotrowski Klaus Kloppstech 《European journal of plant pathology / European Foundation for Plant Pathology》2004,110(7):703-711
Leaves of apple (Malus domestica cv. Elstar) were infected with a cloned isolate of the apple scab Venturia inaequalis. The intercellular washing fluid (IWF) of these plants was collected and the variation in the composition of proteins in the IWF was analysed by SDS-PAGE and two-dimensional gel electrophoresis during and after the infection with V. inaequalis, the causal agent of apple scab. The subsequent analysis of induced proteins by electron spray ionization quadrupole time of flight mass spectroscopy revealed the presence of -1,3-glucanase, chitinase, thaumatin-like protein and a cysteine-like protease in M. domestica leaves infected by V. inaequalis. These results were confirmed by immunoblotting with antibodies against some of these proteins. Moreover, a non-specific lipid transfer protein was identified in uninfected leaves: the amount declined to a non-detectable level within the first week after infection by V. inaequalis. The analysis of the IWF of M. domestica cv. Remo, bearing resistances to apple scab, powdery mildew and fire blight, showed a protein pattern comparable to that of the IWF from V. inaequalis infected leaves from cultivar Elstar indicating the constitutive production at least of some of the pathogenesis-related proteins in the resistant cultivar. 相似文献
5.
BACKGROUND: Myclobutanil, a demethylation inhibitor (DMI) fungicide, is an important fungicide for controlling apple scab and powdery mildew. Overuse of this fungicide has led to establishment of scab isolates with reduced sensitivity to this fungicide in several countries. Experiments were conducted to determine the sensitivity of the causal agent of apple scab, Venturia inaequalis (Cooke) Winter, to myclobutanil in the UK, in order to assess whether there is a relationship between fungal insensitivity and the number of DMI applications, and establishing whether fungal sensitivity varied greatly within an orchard. RESULTS: Reduced sensitivity of V. inaequalis to myclobutanil was positively related linearly to the number of DMI applications. ED50 values ranged from 0.028 to 1.017 mg L?1 (average = 0.292) for the baseline population, whereas isolates from two other orchards had much greater ED50 values, ranging from 0.085 to 5.213 mg L?1 (average = 1.852). There was significant variation in fungal sensitivity to myclobutanil among fungal isolates from different locations within a single orchard. CONCLUSIONS: Spatial spread of insensitive isolates of V. inaequalis to myclobutanil is likely to be limited in distance. Conidia may be an important source of primary inoculum. Myclobutanil should still be effective for most field isolates, but its use should be strategically integrated with other groups of fungicides. Copyright © 2009 Society of Chemical Industry 相似文献
6.
Differentiation in populations of the apple scab fungus Venturia inaequalis on cultivars in a mixed orchard remain over time 
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下载免费PDF全文 The ascomycete Venturia inaequalis causes 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 the UK to 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 of V. inaequalis will become dominant during the lifetime of a commercial apple orchard. 相似文献
7.
Xiaomei Liu Shenwen Cao He Zhang Yunxie Wei Jinji Pu 《European journal of plant pathology / European Foundation for Plant Pathology》2017,147(2):313-323
The aim of this study was to confirm the presence of races in populations of the fungus Venturia inaequalis that are able to overcome specific apple scab resistance gene(s) within the major apple-growing areas of Poland. The monitoring was conducted in six orchards located in the north, centre and south of Poland. The study involved the use of 16 differential genotypes for pathogenicity testing conducted under both greenhouse and orchard conditions. In addition, the occurrence of apple scab on 10 apple cultivars containing the Rvi6 gene was assessed in four organic orchards in central Poland. Apple scab was found on their leaves for the first time in Poland in 2010. The use of differential genotypes containing specific resistance genes suggested that 10 apple scab resistance genes had been overcome by V. inaequalis in the orchards monitored in this study. 相似文献
8.
Evaluations of plant resistance to pathogens are rarely made using isolates from wild habitats, although the heterogeneity of such habitats may generate pathogen diversity which could be a source of new virulence in cultivated habitats. The aim of this study was to investigate whether scab resistance factors, identified and characterized in apples using isolates of Venturia inaequalis from a cultivated habitat, remained effective against isolates from a wild habitat. Three V. inaequalis core collections originating from the cultivated apple Malus × domestica and from two wild species, M. sieversii and M. sylvestris, were established to maximize pathogen diversity. For each core collection, 10 isolates were inoculated in mixtures onto 51 genotypes from an apple progeny segregating for two qualitative resistance genes and six quantitative resistance loci (QRL). On each apple genotype, isolates that contributed to the scab symptoms were identified within the mixture using microsatellite markers. The most frequently detected isolates were inoculated singly to compare their aggressiveness according to their host origin. The results showed that isolates from a wild habitat were able to infect the susceptible apple genotypes. However, these isolates were never more aggressive than isolates from the cultivated habitat on the resistance factors tested. It can therefore be concluded that the resistance factors used in this study, identified with V. inaequalis isolates from a cultivated habitat, remained effective against isolates from M. sylvestris and M. sieversii. 相似文献
9.
苹果黑星病是辽宁省植物检疫对象。目前主要分布于小苹果栽植区及大、小苹果混栽区,已接近辽宁南部的大苹果主产区。经自然感病和人工接种证明,大、小苹果上的黑星病菌可以交互侵染,目前一些主栽的大苹果品种均能感染此病。辽宁地区苹果黑星病的初次侵染来源是落地越冬病叶上于翌春产生的子囊孢子。分生孢子不能越冬成活。苹果枝条及芽鳞不带菌。黑星病菌的两种孢子随气流传播,使病害逐步扩大蔓延。经过6年的观察,苹果黑星病发生始期早晚及发病轻重,与早春和夏季的降水量多少成正相关。田间药剂防治试验结果,以托布津、乙磷铝、多菌灵、特克多等药剂防治效果良好。 相似文献
10.
The relative importance of conidia and ascospores as primary inoculum of Venturia inaequalis in a southeast England orchard 下载免费PDF全文
下载免费PDF全文 Apple scab, caused by Venturia inaequalis, can lead to large losses of marketable fruit if left uncontrolled. The disease appears in orchards during spring as lesions on leaves. These primary lesions are caused by spores released at bud burst from overwintering sources; these spores can be sexually produced ascospores from the leaf litter or asexual conidia from mycelium in wood scab or within buds. The relative importance of conidia and ascospores as primary inoculum were investigated in an orchard in southeast England, UK. Potted trees not previously exposed to apple scab were placed next to (c. 1 m) orchard trees to trap air‐dispersed ascospores. Number and position of scab lesions were assessed on the leaves of shoots from both the potted trees (infection by airborne ascospores) and neighbouring orchard trees (infection by both ascospores and splash‐dispersed, overwintered conidia). The distribution and population similarity of scab lesions were compared in the two tree types by molecular analysis and through modelling of scab incidence and count data. Molecular analysis was inconclusive. Statistical modelling of results suggested that conidia may have contributed approximately 20–50% of the primary inoculum in early spring within this orchard: incidence was estimated to be reduced by 20% on potted trees, and lesion number by 50%. These results indicate that, although conidia are still a minority contributor to primary inoculum, their contribution in this orchard is sufficient to require current management to be reviewed. This might also be true of other orchards with a similar climate. 相似文献
11.
V. Caffier B. Le Cam P. Expert M. Tellier M. Devaux M. Giraud M. Chevalier 《Plant pathology》2012,61(5):915-924
Atypical scab‐like symptoms were reported for the first time in 2007 in the south of France on fruits of apple cultivars carrying the Rvi6 (=Vf) major resistance gene to Venturia inaequalis. With microscopic observations, nucleotide sequence data and pathological tests, it was shown that the causal agent was Venturia asperata. Scanning electron microscopy was used to compare its infection process and conidiogenesis to those of Venturia inaequalis on apple and Venturia pirina on pear. Venturia asperata produced fewer hyphae and fewer spores than the two other Venturia species, and resulted in weaker symptoms. This fungal species was previously described as a saprotroph on apple leaf litter. This is the first report of damage on apple fruits caused by V. asperata. Changes in host and cultural practices may have created a new context favourable for the emergence of this pathogen. It was also detected on symptomless leaves and on overwintered leaves on the ground. Pseudothecia developed on overwintered leaves and released ascospores over a 2‐month period from the end of March until the end of May, suggesting that the fungus is able to survive from season to season. However, it is not yet known if this new disease will establish over coming years and become an emergent disease. 相似文献
12.
V. Caffier F. Didelot B. Pumo D. Causeur C. E. Durel L. Parisi 《Plant pathology》2010,59(6):1072-1080
For sustainable management of scab‐resistant apple cultivars, it is necessary to understand the role of aggressiveness in the adaptation of Venturia inaequalis populations and particularly the costs to the organism of acquiring additional virulence. The aims of the present study were (i) to identify the quantitative variables that are most important in determining the differences in aggressiveness among groups of V. inaequalis isolates, and (ii) to ascertain whether virulent and avirulent isolates of V. inaequalis differ significantly in aggressiveness. The aggressiveness of eight isolates that differed in their virulence to the major resistance gene Rvi6 was compared on the non‐Rvi6 apple cv. Gala. Three components of aggressiveness, namely lesion density, the number of spores per square centimetre of leaf area, and the number of spores per lesion, were evaluated 21 days after inoculation, and the kinetics of lesion density over time were analysed in terms of maximum lesion density, length of latent period and rate of lesion appearance. On the second youngest but fully developed leaf at the time of inoculation, maximum lesion density in the virulent group was 20% lower and the latent period 7% longer, than in the avirulent group. However, the alternative hypothesis, namely that isolates had adapted to quantitative resistance present in cv. Gala depending on their cultivar of origin, could not be rejected. The analysis of the kinetics of lesion density by a non‐linear mixed‐effect model proved useful in the assessment of aggressiveness. 相似文献
13.
Fiaccadori R Cicognani E Alberoni G Collina M Brunelli A 《Pest management science》2011,67(5):535-540
BACKGROUND: Venturia inaequalis (Cooke) Winter with reduced sensitivity to strobilurins has been reported in several countries, including Italy. This study aimed to characterise the sensitivity to strobilurins of three different types of V. inaequalis population: (a) wild types; (b) from commercial orchards satisfactorily managed with strobilurins; (c) from an experimental orchard with control failures by trifloxystrobin and kresoxim‐methyl. In vitro sensitivity tests included antigerminative activity on population conidia and mycelial growth inhibition on monoconidial isolates. Cleaved amplified polymorphic sequence (CAPS) analysis was used for the detection of G143A substitution. RESULTS: Wild‐type populations showed EC50 values lower than 0.031 mg L?1, while those of orchards with good performance by strobilurins presented EC50 values never higher than 0.063 mg L?1. Samples with scab control failures showed a strongly reduced population sensitivity. Similar differences were confirmed in monoconidial isolates. The G143A substitution was always detected in low‐sensitivity populations, only sometimes in well‐controlled populations and generally not in wild types. CONCLUSIONS: In vitro sensitivity assays were able to discriminate the three population types with different scab management, while the qualitative PCR analysis (CAPS) was only partially reliable. High sensitivity differences among V. inaequalis populations with good and poor field control by strobilurins were observed. Copyright © 2011 Society of Chemical Industry 相似文献
14.
Thomas A. J. Passey Andrew D. Armitage Maria K. Sobczyk Michael W. Shaw Xiangming Xu 《Plant pathology》2020,69(4):669-676
Apple scab is one of the most economically important diseases of apples worldwide. The disease is caused by the haploid ascomycete Venturia inaequalis. Growing apples in cultivar mixtures may reduce disease severity. To determine how the pathogen population structure is affected by host mixtures we studied 24 V. inaequalis isolates sampled from three different apple cultivars (Bramley, Cox, and Worcester) growing in a mixed orchard approximately 50 years old. The isolates were aligned against a reference genome and single nucleotide polymorphisms (SNPs) were called between the isolates. The populations isolated from Bramley and Worcester were distinct, while Cox isolates were an admixture. This supports previous tests of the ability of isolates to cross-infect hosts, and molecular comparisons using simple sequence repeats (SSRs). Genotype-specific allele (GSA) loci were not distributed randomly across contigs in proportion to contig length, but were clustered. Clustered GSA loci were observed in almost all contigs. This indicates population differentiation across the whole genome, presumably due to lack of crossing-over events between Bramley and Worcester isolates. This lack is probably due to physical separation effects: sexual mating is more likely to take place and succeed between isolates from lesions on the same leaf than from contact between independently infected leaves in leaf litter on the orchard floor. This would especially be the case if sexual reproduction is initiated before leaf-fall. 相似文献
15.
16.
Characterization of Neofabraea vagabunda isolates causing apple bull's eye rot in Italy (Emilia‐Romagna region) 下载免费PDF全文
下载免费PDF全文 I. Cameldi F. Neri M. Menghini A. Pirondi I. M. Nanni M. Collina M. Mari 《Plant pathology》2017,66(9):1432-1444
Neofabraea vagabunda is the prevalent cause of bull's eye rot, one of the main postharvest diseases of apple, in many producing areas, but its biology has not been studied in detail. The molecular identification, by DNA sequencing of the β‐tubulin region, of 41 isolates collected from apples showing bull's eye rot in the Emilia‐Romagna region confirmed N. vagabunda as the main species in Italy. A biological and morphological characterization of N. vagabunda isolates was performed in vitro. Assays at temperatures ranging from 0 to 30 °C carried out on 10 isolates demonstrated: (i) a marked influence of temperature on colony morphology, conidial production, conidial size and mycelial growth, showing the cold‐tolerant character of N. vagabunda; and (ii) that culture at 15 °C on tomato agar (TA) for 14 days is a rapid and reliable method to favour pathogen conidial production. Trials performed on 38 isolates using these incubation conditions recorded the presence of two N. vagabunda morphotypes, differing for colony morphology, conidial size, conidiomata formation and temperature requirement. The alkalizing ability of the pathogen during growth on TA was also demonstrated for the first time. The pathogenicity of 25 N. vagabunda isolates was proved in vivo on artificially infected Cripps Pink apples. A pH increase was also recorded in apple tissue infected by N. vagabunda isolates (on average 0.2 and 0.3 units of pH after 60 and 120 days of incubation, respectively), suggesting that the N. vagabunda transition from quiescence to necrotrophic colonization in apples could involve the secretion of alkalizing compounds. 相似文献
17.
The project ‘Promotion of Biological Methods in Apple Growing’ which started in Switzerland in 1985 concentrates on the control of Venturia inaequalis (scab) and Podosphaera leucotricha (powdery mildew). The project considers the selection of suitable cultivars resistant or only slightly susceptible to fungal diseases and the assessment of tolerable economic loss. It also includes curative treatments with sterol-synthesis-inhibiting fungicides, according to scab infection periods, as well as applications of plant extracts (proposed by the Institute of Biological Husbandry) and suspensions of antagonists or their culture filtrates as plant-protecting agents. Screening experiments on apple seedlings showed that root extracts of Rumex obtusifolium significantly reduced powdery mildew infections under greenhouse conditions. In field experiments treatments with R. obtusifolium extracts at intervals of 7–10 days were less effective. Saponin-containing extracts of different plants gave satisfying control of scab on seedlings in the growth chamber but were not very effective in the field. Applications of spore suspensions and culture filtrates of the phyllosphere fungi Chaetomium spp. reduced scab and mildew infections on apple seedlings to some extent. It was found that in the last 2 years even primary infections of P. leucotricha were severely parasitized by Ampelomyces quisqualis. Preliminary studies showed that the lack of efficacy of this biocontrol system is due to the delayed spread of the hyperparasite. 相似文献
18.
Ascospores of Mycosphaerella pomi, the pathogen of Brooks fruit spot of apple, were produced in pseudothecia on previously infected and overwintered apple leaves from late April through early August in Aomori Prefecture, Japan. In June 2003, the ascospores were germinating and producing Cylindrosporium-type conidia on apple fruit and leaf surfaces in an orchard. After ascospores were sprayed on apple leaves, Cylindrosporium-type conidia developed on the leaf surfaces. Such Cylindrosporium-type conidia caused typical symptoms of Brooks fruit spot on apple trees after inoculations. These results suggested that the Cylindrosporium-type conidia also serve as an infection source, in addition to the ascospores, for Brooks fruit spot in apple orchards. 相似文献
19.
M. Gerlagh H.M. Goossen-van de Geijn A.E. Hoogland P.F.G. Vereijken 《European journal of plant pathology / European Foundation for Plant Pathology》2003,109(5):489-502
White mould disease leads to production of sclerotia, which subsequently survive in soil and may be responsible for future epidemics. The effect of the mycoparasite Coniothyrium minitans in decreasing survival of sclerotia of Sclerotinia sclerotiorum was studied. Infection of sclerotia of S. sclerotiorum by C. minitans can be achieved by a single conidium. Under optimal conditions, 2 conidia per sclerotium produced 63% of the maximum infection (ca. 90%) of sclerotia produced by up to 1000 conidia. Similar results were observed on the infection of stem pieces infected by S. sclerotiorum. In field trials, application of conidial suspensions of C. minitans to a bean crop soon after white mould outbreak led to a higher percentage of sclerotial infection than later applications. Ninety per cent infection of sclerotia was obtained within 3 weeks of application by C. minitans suspensions in the range of 5 × 105 and 5 × 106 conidia ml–1 at 1000 l ha–1. The concentration of the conidial suspensions and the isolate used were of less importance. The result was marginally affected by the germinability of the conidia (75% against 61% infected sclerotia at 91% and 16% viability of isolate IVT1, respectively). Less apothecia of S. sclerotiorum developed in soil samples collected after 2 months from plots sprayed immediately after disease outbreak than from those treated 11–18 days later. It is concluded that a suspension of 106 conidia ml–1 in 1000 l ha–1 (= 1012 conidia ha–1) sprayed immediately after the first symptoms of disease are observed, results in > 90% infection of sclerotia of S. sclerotiorum. The infection of sclerotia, which prevents their carry-over, occurs within a broad range of inoculum quality. 相似文献
20.
Jorunn Børve Arne Stensvand 《European journal of plant pathology / European Foundation for Plant Pathology》2017,147(4):943-948
Fungi within the Colletotrichum acutatum species complex occur asymptomatically on plant parts of many different plant species. Leaves from apple orchards in southern Norway were sampled, frozen for five hours and incubated for six days to reveal presence of asymptomatic infections of C. acutatum. Number of leaves (incidence) and leaf area covered (severity) with conidial masses of C. acutatum were assessed biweekly on cv. Aroma from late May to late September during three growing seasons. The first finding of conidial masses occurred in the second half of July, and there was a higher incidence occurring in August and September. Sampling of leaves from fruit spurs and vegetative shoots of cvs. Aroma and Elstar showed that conidial masses of C. acutatum developed on leaves on both shoot types, and there was no difference in incidence between these two types. The fungus was detected on leaves from six of eight commercial orchards of cv. Aroma over three years, with a mean incidence of 5.5 %. After storage, bitter rot was found on apple fruit from all eight orchards. There was no correlation between incidence of conidial masses of C. acutatum on leaves and on fruit. In all orchards and seasons investigated, incidence and severity on leaves varied from 0 to 67 % and 0 to 85 %, respectively. The discovery of apple leaves containing conidial masses of C. acutatum clearly indicate for leaves as a potential source of inoculum for fruit infections. 相似文献