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1.
The effects of soil inoculum level and three environmental factors (soil type, soil moisture regime and temperature) on the incidence and severity of powdery scab caused by Spongospora subterranea were investigated in potato plants grown under controlled environmental conditions. Symptoms of powdery scab on tubers were assessed visually, after which DNA was extracted from tuber peelings and quantified in a real-time polymerase chain reaction assay using primers and a TaqMan® probe specific to S. subterranea to establish tuber infection levels. Soil inoculum concentration of S. subterranea did not significantly affect the incidence and severity of either tuber infection or powdery scab symptoms at maturity. No significant differences in disease incidence and severity were found between sandy, loamy and clay soils, although the two lighter soils yielded more powdery scab than clay soil. Constant dampness of the soil resulted in significantly more disease than a fluctuating moisture regime. Infection and disease levels were high at all three temperatures tested (9, 12 and 17°C), but symptoms were most severe at 12°C. The percentage of plants with infected tubers did not increase after tuber initiation, although the amount of S. subterranea DNA detected in tubers and the severity of powdery scab symptoms increased in mature plants. Latent tuber infections were found to be common, especially under conditions suboptimal for disease development. This new information may be important for the prevention of powdery scab in potato-growing areas around the world.  相似文献   

2.
Potato mop‐top virus (PMTV), the cause of spraing in potato tubers, is transmitted by Spongospora subterranea, the cause of powdery scab, and by planting infected seed tubers. This study was undertaken to determine the relative importance of these sources of infection in seed potato production in Scotland. The transmission of PMTV from tested seed tubers to daughter plants was examined over 2 years and six cultivars. The development of foliar symptoms varied with year and cultivar. Infection of daughter tubers derived from PMTV‐infected seed tubers was more prevalent on plants affected by foliar symptoms than those without symptoms. The rate of transmission of PMTV from infected seed tubers to daughter tubers ranged from 18 to 54%. Transmission was affected by cultivar and by origin of seed tubers used for a cultivar, but not by a cultivar's sensitivity to PMTV infection. The incidence of PMTV in daughter tubers of cv. Cara grown from seed potatoes from one source (common origin) by more than 25 seed producers was examined over two successive generations. The incidence of PMTV in daughter tubers was not correlated with that in the seed tubers but appeared to be strongly associated with soil inoculum. The incidence of PMTV was correlated with powdery scab in those crops in which both were present. There was some evidence from soil tests conducted in 2006 using a tomato bait plant and real‐time RT‐PCR that planting PMTV‐infected seed potatoes could increase the risk of introducing the virus into land not infested by PMTV.  相似文献   

3.
This study was undertaken to determine the current occurrence in Scottish seed potato crops of Potato mop‐top virus (PMTV), which is transmitted by Spongospora subterranea and causes spraing (brown arcs and lines) in the flesh of potato tubers, rendering them unsaleable. In 2004, a stratified survey of four commonly grown cultivars was conducted, while in 2007 and 2008, only samples from powdery scab‐affected crops were collected. The incidence of crops in which infection by PMTV was present was 37·5% in the stratified survey in 2004, but was greater in surveys in which tubers with powdery scab were tested (47·2% in 2007 and 44·6% in 2008). Similarly, the frequency of crops with incidences of more than 10% tuber infection was lower (9·4%) in 2004 than in 2007 (25·4%) and in 2008 (26·2%). Significant differences in crop infection were found amongst the four major seed‐producing regions and the counties within these regions. The incidence of crop and tuber infection was least for class Pre‐basic seed potatoes and greatest for class Super Elite 3 and Elite seed potatoes. The results indicate that the prevalence of PMTV has not increased since surveys in the early 1970s.  相似文献   

4.
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5.
The incidence and severity of root infection and root galling caused by Spongospora subterranea were assessed in potato plants (cv. Estima) grown under controlled environmental conditions. The effects of temperature, soil type, soil moisture regime and soil inoculum level on infection and root gall development were determined by molecular and visual methods at two plant growth stages. Root gall severity was scored at harvest, after which DNA was extracted from the roots and quantified in a real-time polymerase chain reaction (PCR) assay specific for S. subterranea . Root galling was severe at 17°C, with a disease score of 3·1 on a 0–4 scale, low (0·6) at 12°C, and did not occur at 9°C. The level of inoculum in soil, in the form of artificially added sporosori, had no effect on the incidence and severity of visual symptoms, with 21%, 41% and 33% incidence observed at 5, 15 and 50 sporosori g−1 soil, respectively. Incidence of infection, as detected by the real-time PCR assay, was greater with increasing soil inoculum concentrations, ranging from 48% at 5 sporosori g−1 to 59% (15 sporosori g−1) and 73% (50 sporosori g−1) of plants infected at maturity, but this effect was not statistically significant. No correlation was found between the occurrence of galls on roots and powdery scab on tubers of the same plants.  相似文献   

6.
Potato tuber necrosis in the form of spraing symptoms is caused by infection with Potato mop‐top virus (PMTV) or Tobacco rattle virus (TRV); spraing has become more important in the Swedish potato crop production. In this study, the presence in Sweden of three potato‐infecting viruses associated with necrotic symptoms in tubers was demonstrated: PMTV, TRV and Tobacco necrosis virus (TNV). This study shows that both PMTV and TRV are frequent in Swedish potato fields. PMTV was found in all Swedish counties, except the two most northern ones. TRV was present at several locations in southern and up to the central parts of Sweden. Both viruses were found further north than observed in earlier surveys. PMTV and TRV were analysed in tubers with spraing symptoms and it was not possible to decide visually if the symptoms were caused by either PMTV or TRV. Furthermore, a high occurrence of symptomless tuber infections was observed for several potato cultivars. A unique observation from this study was a mixed infection of both PMTV and TRV in tubers of cv. Berber, where no visual differences on symptom development were detectable for these tubers compared to single infections. During the survey, tubers of cv. Melody were found to display necrotic symptoms in the skin that are characteristic for the ABC disease. This suggested infection by TNV, which also could be confirmed.  相似文献   

7.
Potato cultivars in elite seed production in Finland were tested for susceptibility to primary and secondary infection by potato mop-top furovirus (PMTV) in field and pot experiments during 1987 and 1988. The tubers of all 22 cultivars tested became infected under favourable conditions in naturally infested soil, and most of them showed external and internal spraing symptoms when stored first at 18°C for 2 weeks and then 2 weeks at 8°C. The second incubation cycle increased the percentage of tubers manifesting symptoms and the halving of tubers also favoured symptom development. The cultivars most tolerant to primary infection were Pito, Hertha and Record, and the most susceptible were Sabina, Olympia, Saturna and Matilda. The same cultivars, excluding Saturna, were also the most susceptible to secondary infection, which decreased tuber yield up to 37%. The virus could be detected fairly reliably in soils by the bait-plant method, and in the tubers after a repeated cycle of incubation at 18 and 8°C. Electron microscopy and serological methods are useful in both virus detection and identification but they still have severe limitations.  相似文献   

8.
The thermal death points of Erwinia carotovora subsp. atroseptica and subsp. carotovora were determined in relation to duration of heat treatment, age of culture and culture medium. No isolates cultured in liquid media survived heating at 53°C for 5 min while those on solid media were killed by heating at 54°C for 10 min. After immersing naturally contaminated potato tubers for 10 min in water at 55°C, Erwinia could not be detected. The same treatment of naturally or artificially contaminated seed tubers gave complete absence of blackleg infection in the field and decreased the amounts of powdery scah(Spongospora subterranea) and black scurf (Rhizoctonia solani) on progeny tubers.  相似文献   

9.
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10.
Potato mop-top furovirus (PMTV) was isolated for the first time in Sweden in 1985. During 1986 and 1987, soil samples from potato fields, mainly in the south-west of Sweden, were tested for PMTV. The virus was detected in 49 out of 305 samples tested. PMTV was also found to be present in soil collected from potato riddles during potato grading in early spring. The soil samples were tested by using Nicotiana clevelandii and N. debneyi as bait plants in a glasshouse. Seven potato cultivars were grown in a PMTV-infested field. PMTV symptoms in the tubers, i.e. external and/or internal brown rings and arcs (spraing), were observed in cvs Evergood, Provita, Saturna and Ukama but not in cvs Bellona, Bintje or King Edward. Very few, or no, PMTV symptoms were found in tubers of susceptible cultivars when examined 2-3 weeks after lifting. In later examinations spraing appeared and increased. The increase was greater in tubers stored at 9°C than in those at 4°C, and in cut than in uncut tubers.  相似文献   

11.
A time-saving and cost-effective polymerase chain reaction (PCR)-based method was developed for species-specific detection of the scab pathogens ( Streptomyces scabies and S. turgidiscabies ) prevalent in potato ( Solanum tuberosum ) in northern Scandinavia. Species specificity of primers was verified using a collection of previously characterized Streptomyces strains isolated from potato scab lesions in Finland and Sweden. A total of 1245 scab lesions was tested from potato cvs Matilda and Sabina grown in the field in two geographic regions of Finland in 2000 and 2001. Freshly harvested or stored potato tubers were incubated at room temperature (18–21°C) under humid conditions for a few days. Bacterial growth was collected from scab lesions for DNA isolation and PCR. The two scab pathogens were detected in the same potato fields, tubers and scab lesions. The relative incidence of S. scabies was high in freshly harvested tubers but was much lower than that of S. turgidiscabies following storage. Both pathogens were seed-transmitted in Matilda and Sabina after 24 weeks of storage at 4°C.  相似文献   

12.
Infection of several commercially important potato cultivars with Tobacco rattle virus (TRV) can result in systemic infection with M-type virus, which persists through generations of vegetative propagation, although spraing symptoms in the tubers rarely develop. In field trials of nine such cultivars it was shown that TRV infection can delay plant emergence and retard subsequent growth, reduce tuber yield and mean tuber weight, increase tuber numbers and the proportion of small tubers, increase the incidence of growth cracks and misshapen tubers, diminish dry matter content, and exacerbate after-cooking blackening. Each cultivar was affected differently, showing different combinations and degrees of these effects. Virus concentration in leaf extracts from individual plants was also highly variable. These, and other potato cultivars similarly susceptible to TRV, are grown on large areas of UK and European potato land. The implications of growing such cultivars for the seed, ware and processing sectors of the potato industry are discussed.  相似文献   

13.
Information is reviewed on root infection of potato by the plasmodiophorid Spongospora subterranea f. sp. subterranea. This pathogen has long been recognized as the cause of root galls (hyperplasia) and the economically important disease powdery scab on tubers (modified stolons). The significance for plant productivity of the zoosporangium stages of the pathogen in potato roots has only recently begun to be documented. Two experiments are described that assessed effects of S. subterranea root infection on potato plant root function and productivity. A greenhouse experiment measured root function and plant parameters for eight potato cultivars with markedly different susceptibilities to tuber powdery scab. Water uptake and plant growth were reduced by S. subterranea inoculation in all eight cultivars. The magnitudes of these negative effects, and intensities of root hyperplasia, differed among the cultivars, but were not related to respective susceptibilities to tuber powdery scab. A field trial assessed root function and plant productivity for a cultivar (Iwa) that is very susceptible to Spongospora tuber and root diseases. Soil water content beneath uninoculated plants was consistently less than for inoculated plants, indicating that inoculation reduced water uptake (root function). Inoculation reduced shoot and root dry weights, and reduced weight of tubers per plant by 42%. Spongospora subterranea causes three diseases of potato: root membrane dysfunction, root hyperplasia and tuber powdery scab. The root diseases caused by the pathogen are likely to be important both for powdery scab management and for deleterious effects on potato crop yields.  相似文献   

14.
马铃薯粉痂病由Spongospora subterranea f.sp.subterranea引起,是典型的土传病害,主要危害块茎和根部。2004年调查了昭通市和会泽县7个乡镇,8个马铃薯品种的粉痂病发生情况。在调查的品种中,会-2发病最轻,平均发病率27%。会泽县马铃薯粉痂病平均发病率59%,昭通市马铃薯粉痂病平均发病率35%。分析土壤中氮、磷、钾、有机质含量及pH与发病率的关系。PB06发病率与土壤中氮、有机质呈正相关,与磷、钾、pH呈负相关,其中与钾含量相关系数为0.693。会-2发病率与土壤pH、钾含量呈负相关,相关系数分别为0.384、0.858,其中与钾含量相关性显著;与磷、有机质含量呈正相关,相关系数分别为0.727、0.323;与氮含量呈正相关,相关系数为0.993,相关性显著。  相似文献   

15.
Variant somaclones of potato cultivar Russet Burbank, selected for resistance to common scab using in vitro cell selection techniques, were tested for resistance to powdery scab, another important disease of potato caused by Spongospora subterranea. This pathogen also invades roots, producing root galls. Most variants consistently showed increased resistance to powdery scab, both in field and glasshouse challenge, when compared to the parental cultivar, several significantly so. On average, the best variant reduced powdery scab incidence by 51% and severity (tuber surface coverage) by 64%. In contrast, no improvement in the extent of root infection and root galling was seen. These results suggest host interactions during root and tuber infection are distinct. Correlation analyses of disease indices amongst the selected variants showed no association between Sp. subterranea root infection and gall scores, nor between root infection and tuber disease severity. However, a weak positive association was found between root gall score and tuber disease, and a strong correlation between tuber disease incidence and severity scores. Interestingly, positive correlations were also found between the extent of powdery and common scab resistance expressed and both incidence and severity of these diseases within the variants, suggesting a common defence mechanism. The role of thaxtomin A in selecting for concurrent resistance to both diseases is discussed.  相似文献   

16.
The incidence of potato pathogens on healthy roots of micropropagated (MP) and seed tuber (ST) plants was examined on successive dates during the growing season in two field experiments. Microplants were grown in a glasshouse for 4–5 weeks in perlite or peal-based substrates, and exposed or not to natural inoculum before planting in the field. The seed tubers originated from stocks of visually clean or moderately blemished tubers and were surface-sterilized or not before planting. Polyscytalum pustulans and Helminthosporium solani only infected roots of ST plants and inoculated MP plants. The incidence of P. pustulans was affected by seed tuber-borne inoculum and, in I year, by the substrate. H. solani was detected infrequently on roots. Rhizoctonia solani was present at low frequencies in most root samples, and more ST than MP plant roots were colonized; there were no substrate effects. In 1 year, increased inoculum levels increased root infection, but only in MP roots. Colletotrichum coccodes occurred at high frequencies and was most common in roots of ST plants. Progeny tubers showed some treatment effects when tested in September and after storage for 6 months, but there were no consistent relationships between root and progeny tuber infection.  相似文献   

17.
Potato seed certification is a disease management tool that minimises the risk of spreading seed tuber-borne inoculum of infectious diseases. Traditionally, certification sampling strategies have relied upon visual assessment of a seedlot from samples taken at one or two points within the load of seed tubers. However methodologies in selection of tuber samples have not been critically assessed for their precision in estimating disease load. This study presents an analysis of 37 potato seedlots over a 3 year period. Analysis of sample data using receiver operating curves (ROCs) indicates that point sampling taking two samples of 100 tubers at the beginning and end of a seedlot gives equivalent disease estimation as a continuous sampling strategy taking ten samples of 20 tubers randomly throughout the seedlot, although at lower statistical precision. This was confirmed both by visual assessment of tuber-borne disease and by analysis of pathogen DNA content from tuber peel. Across the 3 years of study, powdery scab and black scurf were the major seed tuber-borne diseases recognised and this corresponded with high levels of pathogen DNA from peel analysis for both Spongospora subterranea and Rhizoctonia solani AG3 respectively.  相似文献   

18.
 马铃薯粉痂菌(Spongospora subterranea f. sp. subterranea)是引起马铃薯粉痂病的病原。本研究根据粉痂菌内部转录间隔区和线粒体DNA的保守区域,分别设计了2对适用于普通PCR的引物A5/A9、C3/C8和1对适用于荧光定量PCR的引物QF/QR,用于检测块茎和土壤样品中的粉痂菌。特异性检测结果表明:引物对A5/A9和C3/C8,以马铃薯粉痂菌DNA为模板,能分别扩增出264和367 bp大小的单一条带,而对其他非靶标DNA无扩增;引物对QF/QR对马铃薯粉痂菌有单一的熔解峰,说明三对引物特异性良好。灵敏性检测结果表明:荧光定量PCR灵敏度为13.8 fg·μL-1,是普通PCR灵敏度的1 000倍。进一步建立循环域值(Ct)与质粒DNA含量的曲线关系,获得标准曲线y=-3.893 9 x+35.228,R2 = 0.9966,呈良好线性关系。通过对不同地区采集的18份带菌种薯和18份带菌土壤进行普通PCR和荧光定量PCR检测,引物A5/A9、C3/C8和QF/QR对带菌种薯检测率均为100%,对带菌土壤的检测率分别为44.44%、66.67%和100%。本研究建立的马铃薯粉痂病菌快速检测方法,能及时、准确地检测带菌种薯和土壤,为马铃薯粉痂病的早期诊断和防治提供依据。  相似文献   

19.
The incidence of Aspergillus niger (black mould) was found to be high on seed produced in hot (desert) climates. The fungus was transmitted from contaminated seeds to the cotyledons and first true leaves of seedling onions grown under controlled conditions. Seedlings grown from contaminated seeds had longer roots but shorter shoots than those grown from healthy seeds. Seed treatment with either benomyl plusthiramat the rate of 2.5 + 2.5 g active ingredient/kg seed or in hot water (15 min immersion at 60°C) eliminated the fungus in a naturally infected seed stock, untreated seed of which gave 30% infected seedlings.  相似文献   

20.
Potato tubers of five cultivais were incubated at five temperatures between 2 and 20°C for 1 month and then inoculated with Phoma exigua var. foveata and stored at 5°C. Larger rots usually developed on tubers previously incubated at the higher temperatures but cultivar differences were greatest where tubers had been incubated at 2°C. In another experiment, rot size was related to the duration of incubation at 20°C before inoculation.
In a series of experiments, tubers were stored at different temperatures after inoculation; other factors (e.g. wound type or r.h.) were also investigated in some of these. Combining the results of all experiments a linear decrease of % wounds infected (logit transformation) with storage temperature was demonstrated. The size of rots was not simply related to temperature, but tended to increase over the range 2–10°C and then stabilized or declined at higher temperatures. Relative humidity treatments of 75% v. 95% did not consistently affect either the incidence of rotting or rot size. The other factors investigated did not usually interact significantly with temperature.
The relevance of the results for resistance testing is discussed and a simple equation relating disease incidence to inoculum levels, type of damage and temperature is proposed.  相似文献   

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