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1.
Beet cyst nematode-resistant cultivars, which were introduced recently, originated from the homozygous inbred line B883. This translocation product was unstable and the transmission of resistance when crossed with a susceptible cultivar did not exceed 94%. Tests with the resistant cultivars in climate cabinets showed a wide variety of resistance against Heterodera schachtii and beet necrotic yellow vein virus (BNYVV), expressed as average numbers of infective units per plant and percentages of resistant plants. In a series of field trials at different levels of infection of H. schachtii, their multiplication rates on all resistant cultivars depended on the initial density, which was caused by the presence of small numbers of susceptible plants. Since tolerance to wilting was also incorporated in B883, reasonable yields were obtained in the presence of H. schachtii. However, at increasing initial densities of H. schachtii, yields decreased considerably, since penetrating juveniles cause a hypersensitivity reaction in resistant plants. Based upon the results of three series of field trials, it was concluded that resistant cultivars should preferably be applied at population densities between 500 and 2000 eggs and juveniles of H. schachtii per 100ml of soil. Cultivars with double resistance against H. schachtii and BNYVV behaved like those with H. schachtii resistance in soils infected with beet cyst nematodes, but not with BNYVV. In soils with a combined infection of H. schachtii and BNYVV double resistant cultivars were far superior to single resistant ones, since damage caused by BNYVV was far more serious than damage caused by H. schachtii. No substantial interaction between soil pathogens nor types of resistance could be detected.  相似文献   

2.
A collection of 241 isolates of Rhizoctonia solani obtained from potato plants grown in different areas in France was characterized for anastomosis grouping, symptomatology on tubers of different cultivars and sensitivity to three fungicides. Most isolates collected belonged to (anastomosis groups (AGs)) AG 3, but 2% and 4% of the isolates were AG 5 and AG 2-1. AG 3 and AG 2-1 isolates were mostly obtained from sclerotia on tubers, but all AG 5, some AG 3 and some AG 2-1 isolates were recovered from superficial tuber alterations, like deformations, corky or scabby lesions. Sclerotia were formed on tubers produced by healthy stem cuttings grown in soil artificially infested with AG 3, but not on tubers grown in soil infested with either AG 5 or AG 2-1. No variation in susceptibility to sclerotial formation was observed among five potato cultivars. In all cases, a large proportion of tubers showed superficial corky lesions, often associated with deformations. The proportion of tubers with lesions and deformations was highest in soil infested with AG 2-1 and significantly lower on cv. Samba in all treatments. All isolates were highly sensitive to flutolanil, iprodione and pencycuron, except the AG 5 isolates, moderately sensitive to pencycuron. These results show that, although AG 3 is the most common R. solani group on potato in France, AG 5 and AG 2-1 may be present. Isolates differed for pathogenicity. In vitro sensitivity to fungicides varied among AGs.  相似文献   

3.
A total of 304Rhizoctonia solani isolates and 60 binucleateRhizoctonia-like fungi were recovered from stems and tubers of infected potato plants over a 2-yr period in northeast Turkey.R. solani isolates were identified to 11 anastomosis groups (AGs): AG-1 (0.66%), AG-2-1 (5.6%), AG-2-2 (0.99%), AG-3 (83.9%), AG-5 (4.6%), AG-6 (0.66%), AG-8 (1.32%), AG-9 (0.33%), AG-10 (1.32%), AG-12 (0.33%), and AG-13 (0.33%). In the greenhouse tests, most of the AG-3 isolates were significantly more virulent than isolates belonging to other AGs on potato cv. Batum. Isolates of other anastomosis groups differed in their virulence. Results indicated that AG-3 is an important pathogen on potatoes grown in the study area. Five of 22 commercial and local potato cultivars evaluated for their reaction toR. solani AG-3 isolates (TP-2) under greenhouse conditions were highly resistant; the remaining cultivars exhibited different levels of susceptibility to the pathogen isolate. http://www.phytoparasitica.org posting July 14, 2005.  相似文献   

4.
水稻纹枯病是由死体营养型真菌立枯丝核菌Rhizoctonia solani AG1-IA亚群引起的一种土传病害,在世界水稻种植区均有发生,是限制水稻高产的主要病害之一。虽然国内外学者针对纹枯病菌已开展了大量的研究工作,但由于该菌寄主范围较广、抗性水稻资源缺乏及其田间抗性鉴定的不稳定性等问题,该病害的研究仍没有取得突破性进展。挖掘自然界中存在的纹枯病抗源材料,选育抗病水稻品种是防控该病害、降低水稻产量损失,从而最大限度保障全球水稻产业可持续发展的有效手段。该文对近年来国内外关于水稻纹枯病菌与寄主的互作分子机制、抗性水稻基因资源挖掘及其抗性机制的最新研究进展进行综述,并提出下一步的重点研究方向,以期为推动水稻对纹枯病的抗性机制解析及抗纹枯病水稻育种提供参考。  相似文献   

5.
Four lines (designated MR0, MR1, MR2, and M8) from 13 accessions of Beta vulgaris subsp. maritima were selected on the basis of phenotypes produced after foliar rub-inoculation with Beet necrotic yellow vein virus (BNYVV). The susceptible phenotype developed bright yellow local lesions, whereas the resistant phenotype had symptoms ranging from no visible lesions to necrotic lesions at the inoculation site. MR1 and MR2 lines had a resistant phenotype depending on the isolate and the MR0 line was susceptible to all isolates of BNYVV tested. The M8 line was highly susceptible; the virus spread systemically and caused severe stunting. These plant lines will be useful for distinguishing BNYVV isolates having different pathogenicities, especially those controlled by RNA3 and/or RNA5.  相似文献   

6.
Sixty-eight Rhizoctonia solani isolates (31 AG-1, 37 of AG-2-2) associated with web blight (WB) of common bean, Phaseolus vulgaris, were examined for sequence variations in the ITS-5.8S rDNA region. The isolates were collected in bean-growing lowland and mountainous regions in Central and South America. Sequences of these isolates were aligned with other known R. solani sequences from the NCBI GenBank and distance and parsimony analysis were used to obtain phylogenetic trees. WB isolates of AG-1 formed two clades separated from known AG-1 subgroups. WB isolates of AG-2-2 formed one clade separated from known AG-2-2 subgroups. Other isolates belonged to AG-1 IA and AG-1 IB. Based on phylogenetic analysis, we confirmed that at least five genetically different subgroups incite WB of common beans. Three new subgroups of R. solani have been identified and designated as AG-1 IE, AG-1 IF and AG-2-2 WB. DNA sequences of these isolates provided needed information to design taxon-specific primers that can be employed in ecological/epidemiological studies and seed health tests.  相似文献   

7.
Powdery mildew (Podosphaera pannosa) is the most important fungal disease in greenhouse roses and is in practice controlled by fungicides. The creation of novel cultivars with durable resistance to powdery mildew is highly desirable. To understand the inheritance of mildew resistance, a tetraploid rose population with a size of 181 seedlings was obtained by crossing two tetraploid genotypes each having partial resistance. The population and its parents were tested under greenhouse conditions with two well-defined monospore isolates (2 and F1) using artificial inoculation with spore suspensions. Disease score at 11 days post-inoculation, latent period and rate of symptom development were used to describe seedling resistance. The tests for both isolates exhibited a wide and significant variation among genotypes for resistance. The distribution of the genotypic means of the disease scores was continuous and showed a considerable transgression. Statistical analysis, scatter plot of disease scores for the isolates, and correlation analyses indicated that the two isolates differed in pathogenicity. The outcome of the tests showed that the inoculation assay with spore suspensions was a reliable and effective way to screen large numbers of genotypes under greenhouse conditions for genetic and breeding studies. This is the first report on spore-suspension inoculation to be used successfully in rose.  相似文献   

8.
The rDNA-ITS sequence of Rhizoctonia solani AG 1-ID was determined and compared to those of R. solani AG 1-IA, AG 1-IB, and AG 1-IC. The similarity of the isolates from each AG 1 subgroup was almost identical (99%–100%), whereas it was lower between subgroups (91%–95%) than within subgroups. Phylogenetic analysis indicated that isolates of AG 1-ID and other subgroups were separately clustered. Isolates of R. solani AG 1 were clearly separated from R. solani AG 2-1, AG 4, and binucleate Rhizoctonia AG-Bb and AG-K. These results showed that analysis of the rDNA-ITS sequence is an optimal criterion for differentiating R. solani AG 1-ID from other subgroups of R. solani AG 1.  相似文献   

9.
小麦品种(系)对纹枯病抗性鉴定及抗病资源的筛选   总被引:7,自引:2,他引:7  
室内苗期采用菌落上直播催芽麦粒法和田间连续 2年采用小麦粒砂土壤接菌法对25个小麦品种进行了抗纹枯病性鉴定。结果表明 ,品种间抗感性存在明显差异 ,室内和田间抗感性表现基本一致 ,田间两个年度间抗感性表现具有相对的稳定性。品种南阳82505、S048、荆麦66等 7个品种室内病级为1.03~1.50 ,田间相对抗病性指数为 0.40~0.79,两个年度均表现为中抗。 1998~2000年度共鉴定品种材料5.48份 ,抗性材料占17.9% ,其中湖北省94-5036、96-951等 11份区预试材料表现为中抗 ,占区预试鉴定材料总数的 20.8%。  相似文献   

10.
A rapid resistance/susceptibility test for Peronospora parasitica (downy mildew) was established by inoculating leaf-disks of four Brassica oleracea accessions. Several conditions were tested: disk disinfection or not, agar medium with or without nutrients and with 50 or 100 ppm of benzimidazole. Using disinfected disks placed on agar (no nutrient and benzimidazole at 50 or 100 ppm), the responses of leaf-disks to four isolates were similar to those obtained using the classical cotyledon test, whereas undesired contaminations occurred in all other conditions. The possible effect of the particular leaf used for obtaining the disks was also studied. In each incompatible interaction tested, disks were resistant whatever the leaf used. In compatible interactions, susceptible phenotypes were observed on disks derived from the six lowest leaves, but disks from upper leaves were resistant. The genetic basis of resistance in a F1 hybrid broccoli was assessed, by testing six isolates on an F2 population derived from this hybrid. The cotyledon test only allows inoculation of two isolates per seedling, whereas many isolates can be tested on each plant by using leaf-disks. The segregation of the resistance to each of the six isolates was analysed: two dominant genes (tightly linked) control resistance to all isolates (one to five isolates; the other to only one isolate).  相似文献   

11.
Small differences in activity between batches of purified beet necrotic yellow vein virus (BNYVV) were observed in ELISA. A four-parameter modelled dose-response curve of purified BNYVV was used for the conversion of ELISA values to virus concentrations. Seedlings of the susceptible cultivar Regina and the partially resistant cultivars Nymphe and Rima were tested for resistance to BNYVV in a mixture of sand and infested soil. Plants were grown in a green-house with low nutrient supply and at temperatures below the optimum of both the vectorPolymyxa betae and BNYVV. Root systems were small and consisted mainly of lateral roots. Significant differences in average virus concentrations were found between cultivars, both when using the complete root systems and when using either the top or the bottom part of the root systems. Average virus concentrations in Regina were always significantly higher than in Rima and higher than in Nymphe on all occasions except one (P<0.05). Differences between Nymphe and Rima were less evident. Variation between plants was greatest within Rima. The test described in this paper can be used for the discrimination of different cultivars and for the identification of individual plants with resistance to BNYVV.  相似文献   

12.
为明确山东省玉米纹枯病菌对噻呋酰胺的敏感性及其抗药性风险,采用菌丝生长速率法分别测定了采自山东泰安、临沂、潍坊、莱芜、日照及青岛6个地区的102株玉米纹枯病菌对噻呋酰胺的敏感性。结果表明:其EC50值分布范围为0.010~0.194 μg/mL,平均EC50 值为 (0.086 ± 0.004) μg/mL,且敏感性呈连续单峰曲线分布。通过紫外诱导与药剂驯化的方法各获得5株耐药性菌株 (TA3-X2、TA17-X6、LY8-3、QD14-Y7和WF6-A2) 和1株抗性突变体 (QD2-Y4),其抗性水平在6.46~20.08倍之间,突变频率分别为0.87%和0.52%。对抗性突变体生物学性状的研究表明,紫外诱导获得的5株耐药性菌株其耐药性不能稳定遗传,而经药剂驯化获得的1株抗性突变体QD2-Y4的抗药性可稳定遗传;耐药性菌株TA3-X2的菌丝生长速率高于亲本菌株,其余菌株与亲本菌株差异不明显;5株耐药性菌株和1株抗性突变体的菌丝干重和菌核干重均低于亲本菌株;TA3-X2、WF6-A2及QD2-Y4的致病力低于亲本菌株,TA17-X6、LY8-3及QD14-Y7的致病力与亲本菌株无明显差异。交互抗性测定表明,噻呋酰胺抗性突变体与戊唑醇、丙环唑、咯菌腈、井冈霉素、苯醚甲环唑和多菌灵之间均无交互抗性,与啶酰菌胺和氟唑菌苯胺之间则存在交互抗性。研究表明,山东省6个地区的玉米纹枯病菌对噻呋酰胺比较敏感,推测噻呋酰胺可作为防治玉米纹枯病的理想候选药剂。  相似文献   

13.
Common bacterial blight (CBB) in edible beans (Phaseolus vulgaris), incited Xanthomonas campestris pv. phaseoli, reduces bean yields and seed quality. The main objective of this study was to determine resistance to common bacterial blight in bean genotypes. Twenty-two bean genotypes grown in Turkey including common and snap bean cultivars/lines were collected from different parts of Turkey and tested for resistance against to Xanthomonas campestris pv. phaseoli strain MFD-11. All the common and snap bean lines/cultivars tested were moderately susceptible, susceptible or highly susceptible, except AG-7117 which was found resistant to Xanthomonas campestris pv. phaseoli. This is the first report of a resistance source in a common bean line (AG-7117) against Xanthomonas campestris pv. phaseoli.  相似文献   

14.
Rhizomania, caused by Beet necrotic yellow vein virus (BNYVV), is vectored by Polymyxa betae. The disease can only be controlled by growing partially resistant sugar beets, which quantitatively reduce virus replication and spread. None of the known major resistance genes (Rz1, Rz2, Rz3), alone or in combination, are able to prevent BNYVV infection entirely. Here we report for the first time the identification of a Spanish soil, containing an A-type BNYVV with RNA 1-4, displaying Rz1 resistance-breaking abilities comparable to soils from the USA and to those from France containing the French (Pithiviers) P-type BNYVV with RNA 5. A resistance test with several soil samples vs. different sugar beet cultivars was conducted under standardised conditions. Sugar beets were analysed after 12 weeks of greenhouse cultivation for taproot weight, BNYVV and relative P. betae content. The soil samples from Spain, France and the USA produced high virus contents and strong rhizomania symptoms in Rz1 plants, indicative of resistance-breaking abilities. In addition, all resistance-breaking soil samples produced detectable virus concentrations in plant lateral roots of the Rz1 + Rz2 cultivar, and plants grown in the Spanish soil sample also had reduced taproot weight and displayed severe rhizomania disease symptoms. Additionally, the main pathogenicity factor P25, responsible for the formation of BNYVV symptoms, showed high sequence variability in the amino acid tetrad at position 67–70. The results suggest the geographically independent selection of BNYVV resistance-breaking isolates following the uniform cultivation of Rz1-containing sugar beet cultivars.  相似文献   

15.
Field experiments were conducted during 1997 and 1998 to determine the effects of sugar beet cultivar susceptibility to Cercospora leaf-spot on the sensitivity ofCercospora beticola isolates to the triazole fungicide flutriafol. Four cultivars with different levels of disease resistance were treated in experimental plots with six spray applications of flutriafol. Disease assessments were carried out at 15-day intervals. Sensitivity to flutriafol was measured on isolates collected from the plots ∼15 days after the last flutriafol application. Measurements of disease severity and calculations of AUDPC (area under disease progress curve) values showed a distinct differentiation among cultivars, reflecting their level of disease resistance. Disease severity was significantly lower in cvs. ‘Bianca’ and ‘Areth’ than in ‘Univers’ and ‘Rizor’ both in the untreated and in the flutriafol-treated plots. Fungal isolates from flutriafol-treated plots were less sensitive to the fungicide than were isolates from untreated plots. However, no differences in isolate sensitivity were observed among the cultivars, as regards their level of disease resistance. Despite the fact that the use of resistant cultivars cannot eliminate selectively the resistant strains, it can eliminate both resistant and sensitive isolates. Reducing the number of treatments with DMIs, by applying them only when environmental conditions are favorable for disease development, is a prerequisite for successful resistance management; therefore, the use of disease-resistant varieties could aid toward management of DMIs resistance inC. beticola. http://www.phytoparasitica.org posting May 6, 2003.  相似文献   

16.
A new disease of sugar beet called Syndrome des Basses Richesses, which appeared in Burgundy and Franche-Comté, France, in 1991, is of uncertain aetiology. However, evidence for aerial transmission of the disease, symptom similarity with yellow wilt and preliminary results of phytoplasma detection, support the hypothesis of a phytoplasma being associated to the disease. A search for a natural phytoplasma vector, was conducted in Franche-Comté in 1997 and 1998, in an area where sugar beet crops had been affected since 1996. A cixiid, tentatively identified as Pentastiridius beieri, not described in the preceding years and not formerly reported as a phytoplasma vector, was present in sugar beet plots in high populations from June to August in 1997 and 1998. Individuals were captured and used for transmission experiments to periwinkle and sugar beet seedlings. They were further tested for the presence of a phytoplasma in their body, using PCR amplification of 16S rDNA of phytoplasmas. In 1997 and 1998, from 2% to 13.3% of the individuals carried a stolbur phytoplasma and insects which tested positive, appeared to have transmitted, through feeding, a stolbur phytoplasma to periwinkles and to sugar beets. This cixiid, whose vectoring capacity of stolbur phytoplasma to plants, is now clearly demonstrated, is available for experimental inoculations, in order to examine the role of phytoplasmas in the Syndrome des Basses Richesses, through the observation of symptom expression in phytoplasma-inoculated plants.  相似文献   

17.
采用浸叶法测定了北京地区6个粘虫Mythimna separata(Walker)田间种群对5种不同类型杀虫剂的抗药性。结果表明:与相对敏感品系相比,6个田间种群对5种杀虫剂均表现出不同程度的抗性水平。其中,对氯虫苯甲酰胺(抗性倍数为1.314~4.213)、甲氨基阿维菌素苯甲酸盐(抗性倍数为1.000~4.385)和毒死蜱(抗性倍数为1.083~5.936)表现为敏感至低水平抗性;对虫螨腈(抗性倍数为1.355~20.80)和氯氟氰菊酯(抗性倍数为1.748~13.98)表现为敏感至中等水平抗性。因此,北京地区的粘虫防治应注重将氯虫苯甲酰胺、甲氨基阿维菌素苯甲酸盐和毒死蜱与虫螨腈或氯氟氰菊酯交替或轮换使用,以延缓抗药性的产生与发展。  相似文献   

18.
The legume species Medicago truncatula is gaining interests as a plant for structural and functional genomics that can be used to identify agronomically important genes in crop legumes. Resistance to the alfalfa rust (Uromyces striatus) was studied in a germplasm collection of M. truncatula. Accessions varied in resistance, as expressed by disease severity, but none showed macroscopically visible necrosis. Histological investigations, in selected lines covering the whole range of resistance reactions, revealed little difference in spore germination and none in orientation of germtubes on the leaf surface. However, appressorium formation on the stoma was significantly reduced in some accessions. Differences in resistance among accessions were more evident once the stoma were penetrated by the infection structures. Resistance was mainly due to a restriction of haustorium formation with varying levels of early abortion of the colonies, a reduction in the number of haustoria per colony, and hampered colony growth. In addition, necrosis of the host cells associated with infection hyphae was detectable in some accessions from the beginning of colony development. This information will be useful for eventual mapping and cloning analyses of resistance genes in M. truncatula that will in turn be useful for understanding other legume/rust interactions.  相似文献   

19.
Head rot is a major disease of broccoli caused by the soft rot pathogens Pseudomonas fluorescens and Erwinia carotovora. Two in vitro pathogenicity tests were evaluated as a methods to identify broccoli cultivars susceptible or resistant to bacterial head rot. One test used mature heads excised from the plant and inoculated with squares of cotton lint which had been soaked in a bacterial suspension. The other test involved stab-inoculating axenically grown seedlings. With the excised head test, susceptible cultivars showed a black soft rot, whilst less susceptible or moderately resistant cultivars showed only watersoaking, or browning and slight softening of the tissue. No cultivar was completely resistant. Ten cultivars were tested, and their susceptibility ratings corresponded with previously recorded field data, with one exception. This laboratory test could be used to screen for susceptibility to head rot in broccoli breeding programmes. The seedling test distinguished differences in aggressiveness among bacterial isolates but not cultivar susceptibility. Increasing head size correlated negatively with disease resistance. Head shape, i.e. cultivars which showed a domed shape rather than a flat shape, was positively correlated with disease resistance. Thus small domed heads are more resistant to head rot than large flat heads. Other morphological characteristics, viz. floret prominence and number, and sepal stomatal number were not correlated with host resistance.  相似文献   

20.
Solacol®, a formulation of the antibiotic validamycin, at 0.33% in 2% malt extract agar, reduced the spread of fungi on dilution plates drastically and allowed twice as much incubation time before subculturing; this resulted in an elevated number of species isolated. Using pure cultures of 62 common soil fungi, it was shown that all fast-growing species (exceptPythium ultimum) were efficiently inhibited but not completely suppressed. Inhibition was comparable to that by 0.5% oxgall, though, while this substance completely suppressed several species, Solacol very strongly inhibited onlyGaeumannomyces graminis, Gerlachia nivalis, Harzia acremonioides, Verticillium biguttatum andRhizoctonia solani. In a further experiment each separate constituent of Solacol was tested against 22 fungi at equivalent concentrations. Validamycin strongly inhibitedChaetomium globosum and two Basidiomycetes, though hardly more than the non-ionic detergent which mainly inhibited the other fungi. A few species were, however, more inhibited by Solacol than by the detergent alone. Solacol at 0.33% is a suitable aid in dilution plating of soil fungi, by increasing the number of colonies and species observed.Samenvatting Solacol®, een formulering van het antibioticum validamycine, remde de groei van schimmels in verdunningsplaten met een concentratie van 0.33% in 2% moutagar en maakte het mogelijk de periode tot afenten met een factor 2 te verlengen; daardoor was het aantal geïsoleerde soorten duidelijk toegenomen. Met reincultures van 62 algemene grondschimmelsoorten werd aangetoond, dat alle snelgroeiende soorten (met uitzondering vanPythium ultimum) voldoende geremd, maar niet volkomen onderdrukt werden. Het remmingspercentage was vergelijkbaar met dat van 0.5% ossegal, hoewel dit laatste sommige soorten volkomen onderdrukte; Solacol remde alleenGaeumannomyces graminis, Gerlachia nivalis, Harzia acremonioides, Verticillium biguttatum enRhizoctonia solani zeer sterk. In een volgend experiment werden de componenten van Solacol t.o.v. 22 fungi apart getoetst in concentraties equivalent aan 0.33% Solacol. Validamycine remde alleenChaetomium globosum en twee basidiomyceten behoorlijk, maar nauwelijks meer dan de niet-ionische uitvloeier, die in hoofdzaak de overige remeffecten veroorzaakte. Enkele soorten werden echter door het complete Solacol veel sterker geremd dan door de uitvloeier alleen. Solacol in een verdunning van 0,33% wordt aanbevolen bij verdunningsplaten voor het isoleren van grondschimmels ten einde het aantal kolonies en soorten te verhogen.  相似文献   

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