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1.
The pathogenic variability of the barley scald fungus, Rhynchosporium secalis , in central Norway was examined in 1994. The climate in this region is usually cold and wet during the growing season of spring barley. Leaf blotch is prevalent and causes significant yield losses. Forty-two isolates of the fungus, from naturally infected spring barley in four counties, were differentiated into 32 pathotypes by the standard differential set for R. secalis . All pathotypes were complex and had virulence for nine to 22 differentials. The cultivar Osiris was resistant to all isolates tested. The cultivars C.I.8162, Hudson, Atlas 46 and C.I.3515 were resistant to the majority of the isolates. Several differentials with various resistance genes were susceptible to up to 100% of the isolates. Isolates were derived from local cultivars with no known resistance genes, suggesting that R. secalis populations in central Norway are characterized by a high degree of seemingly unnecessary pathogenicity. Because of the great variability and complexity of the pathotypes, traditional breeding methods using single major genes are not likely to be effective in central Norway.  相似文献   

2.
Barley spot blotch (SB), caused by Cochliobolus sativus, is an important barley disease which causes extensive grain yield losses. These losses may not always correlate directly with the amount of diseased leaf area. Two barley cultivars, Quebracho (susceptible to SB) and Carumbé (with intermediate susceptibility to SB), were compared in field experiments in 2003, 2004 and 2006. Plots of each cultivar were either inoculated with C. sativus or protected with fungicide under field conditions to generate contrasting treatments: i) diseased, and ii) free of disease, respectively. SB severity over the growing season, photosynthetic rate on leaves with no visible symptoms and grain yield were assessed for each treatment and year. There was no treatment effect on cv. Carumbé, while cv. Quebracho showed a significant yield reduction, even though SB severity during the grain filling period was <10 %. This yield reduction was associated with a reduced photosynthetic rate at the beginning of the grain filling period in cv. Quebracho. A similar experiment was conducted under greenhouse conditions, adding a treatment without inoculum or fungicide. There were no differences in photosynthetic rate or grain yield per plant among treatments. These results suggest a distinct physiological response to SB infection among cultivars affecting leaf photosynthetic rate, and SB severity may not be the best estimator of yield losses caused by SB.  相似文献   

3.
The infection efficiency and severity of leaf blotch on spring barley inoculated with three pathotypes of Rhynchosporium secalis from central Norway were studied under different temperature and humidity regimes. Seedlings of the cultivar Arve were subjected to two constant temperatures, 13° or 18°C. Dry periods of 8 h or longer before or after a wet period of 4 h, carried out in the first 48 h postinoculation, reduced disease severity assessed 16 days after inoculation. The effect of dry periods of up to 24 h was nullified when plants were subjected to high humidity for 48 h after the dry treatment. The disease developed most rapidly when the wet period was 48 h and the temperature 18°C. At or near the optimum temperature for R. secalis (18°C), leaf wetness duration as short as 2 h resulted in considerable disease. Isolates reacted differently to temperature. The most aggressive isolate caused severe disease irrespective of temperature (56–70% of the leaf area infected); however, disease severity caused by the least aggressive isolate was significantly higher at the optimum temperature compared with a lower temperature (13°C). This information can facilitate evaluation of weather data in relation to predicting leaf blotch for advisory purposes.  相似文献   

4.
The overwintering and the epidemic development in spring of leaf rust was studied in 11 winter barley cultivars at two different sites near Wageningen in 1976/1977. The amount of leaf rust decreased through the winter at both sites. Cultivars differed considerably in the amount of leaf rust in late winter. Both the moment and the rate of increase of leaf rust after the winter varied with cultivars. The ultimate amount of leaf rust in a cultivar was therefore determined by three factors: The amount of overwintering leaf rust, the onset of leaf rust increase and the rate of increase. The latter was determined by the partial resistance of the cultivar. Why the epidemics did not start at the same moment is yet unknown. The differential overwintering could be explained from the amounts of leaf rust and powdery mildew at the start of the winter, the effect of powdery mildew being a negative one. The correlation coefficient between the values observed in March and those predicted from the December leaf rust and powdery mildew readings was 0.93. In a second experiment carried out in 1979/1980 with six winter barley cultivars chosen from the first experiment the powdery mildew was succesfully excluded by treatment with fungicides. There was no decrease in the leaf rust over the winter nor a differential cultivar effect on overwintering.  相似文献   

5.
The effect of barley yellow dwarf virus (BYDV) on the development of net blotch (Pyrenophora eves) and leaf blotch (Rhynchosporium secalis) was examined on seven barley cuitivars. Seedlings were infected with BYDV at the two-leaf stage (G.S. 12). Their susceptibility to three isolates of p teres and isolates of two races (U.K. 1, U.K. 2) of R. secalis was examined at the four-leaf stsge (G.S. 14) and when plants were more mature (G.S. 33/38). At G.S. 14 numbers of lesions produced by P. teres and R. secalis were reduced, on average, by 37 and 72% respectively, and at G.S. 33/38 by 61 and 74%.  相似文献   

6.
Rhynchosporium secalis is one of the most destructive pathogens of barley worldwide, causing yield decreases of up to 40% and reduced grain quality. Rhynchosporium is a polycyclic disease. Primary inoculum includes conidia produced on crop debris, infected seeds and possibly ascospores, although these have not yet been identified. Secondary disease spread is primarily by splash dispersal of conidia produced on infected leaves, which may be symptomless early in the growing season. Host resistance to R. secalis is mediated by both 'major' or host-specific genes (complete resistance) and 'minor' genes of smaller, generally additive effects (partial resistance). Crop growth stage and plant or canopy architecture can modify the expression of resistance. Resistance genes are distributed unevenly across the barley genome, with most being clustered on the short arms of chromosomes 1H, 3H, 6H and 7H, or in the centromeric region or on the long arm of chromosome 3H. Strategies used to manage rhynchosporium epidemics include cultivar resistance and fungicides, and also cultural practices such as crop rotation, cultivar mixtures and manipulation of sowing date, sowing rate or fertiliser rate. However, the high genetic variability of R. secalis can result in rapid adaptation of pathogen populations to render some of these control strategies ineffective when they are used alone. Sustainable control of rhynchosporium needs to integrate major-gene-mediated resistance, partial resistance and other strategies such as customized fungicide programmes, species or cultivar rotation, resistance gene deployment, clean seed and cultivar mixtures.  相似文献   

7.
闫佳会  姚强  陈海民 《植物保护》2016,42(3):212-214
本研究旨在明确青海青稞主栽品种和后备品种对条纹病和云纹病的抗性,以期为抗病育种及田间病害防治提供理论依据。试验采用田间自然病圃法,对青海主栽的30个青稞品种(系)进行了条纹病和云纹病田间抗性鉴定。结果表明,供试青稞品种(系)对2种病害的抗性存在显著差异,但缺乏免疫品种。对条纹病表现高抗的有13个品种(系),占鉴定总数的43.3%,其中主栽品种有3个,即‘门农1号’、‘昆仑13号’、‘巴青1号’。品系17发病率最低。对云纹病表现高抗的有品系1、品系2、品系6、品系17、品系28、RQKQ-3、RQKQ-5、RQKQ-6、RQKQ-7、RQKQ-8、‘门农1号’、‘互青2号’、‘北青6号’和‘昆仑10号’,共14个,其病情指数均在10以下;表现中抗的共有8个,分别为品系5、品系11、RQKQ-1、RQKQ-9、‘巴青1号’、‘北青3号’、‘北青7号’和‘昆仑13号’。  相似文献   

8.
Lettuce cultivars adapted to Californian growing conditions were screened for resistance to fusarium wilt caused by Fusarium oxysporum f.sp. lactucae in order to determine if differences in susceptibility among currently grown cultivars might contribute to management of this disease. Based on a preliminary evaluation of 46 cultivars, eight that were among the most resistant of their horticultural type (iceberg, romaine or leaf) were selected for further testing. The relative susceptibility of these cultivars was assessed by: (i) root-dip inoculation, (ii) sowing seeds into infested potting mix and (iii) transplanting seedlings into an infested field. Evaluations of disease severity showed that both methods (i) and (ii) produced cultivar rankings that were significantly correlated with rankings from field trials [method (iii)]. Two romaine and two leaf cultivars were highly resistant to fusarium wilt (mean disease severity rating of ≤1·3 on a 1–4 scale) under all test conditions. Other romaine and leaf cultivars, however, were highly susceptible in root–dip tests, so there was no consistent association between cultivar type and susceptibility to fusarium wilt. Likewise, there was considerable variation in susceptibility to wilt among iceberg cultivars, but all were significantly more susceptible than the most resistant romaine and leaf cultivars.  相似文献   

9.
The colonization of the roots of four cultivars of subterranean clover by isolates representing four races of Phytophthora clandestina was studied. There was a highly significant race × cultivar interaction in the growth of inoculated tap roots and the degree of colonization of roots by the pathogen. While all races were able to infect the roots of all cultivars tested, roots of the susceptible cultivars were colonized more rapidly and extensively than those of the resistant cultivars. In compatible combinations, fungal colonization extended for a few centimetres in the tap root and lateral roots in the moderately susceptible cultivars Trikkala and Meteora, or throughout the whole root system leading to the death of the host in the very susceptible cultivar Woogenellup. In contrast, limited fungal colonization of the tap root and lack of extension of the fungus into lateral roots was typical of incompatible combinations. In all cultivars, lateral roots were as susceptible to infection as tap roots. The number of lateral roots of Woogenellup was significantly reduced by infection. However, neither the rate of lateral root formation nor the total number of lateral roots of Seaton Park, Meteora and Trikkala was reduced by infection with virulent or avirulent races of the pathogen.  相似文献   

10.
This study follows on from a previous study showing that binary mixtures of wheat cultivars affect the evolution of Zymoseptoria tritici populations within a field epidemic from the beginning (t1) to the end (t2) of a growing season. Here, we focused on the impact of interseason sexual reproduction on this evolution. We studied mixtures of susceptible and resistant cultivars (carrying Stb16q, a recently broken-down resistance gene) in proportions of 0.25, 0.5 and 0.75, and their pure stands. We determined the virulence status of 1440 ascospore-derived strains collected from each cultivar residue by phenotyping on seedlings. Virulence frequencies in the ascospore-derived population were lower in mixtures than in pure stands of the resistant cultivar, especially in the susceptible cultivar residues, as at t2, revealing that the impact of mixtures persisted until the next epidemic season (t3). Surprisingly, after sexual reproduction the avirulence frequencies on the resistant cultivar residues increased in mixtures where the proportion of the susceptible cultivar was higher. Our findings highlight two epidemiological processes: selection within the pathogen population between t1 and t2 driven by asexual cross-contamination between cultivars (previous study) and sexual crosses between avirulent and virulent strains between t2 and t3 driven by changes in the probabilities of physical encounters (this study). Mixtures therefore appear to be a promising strategy for the deployment of qualitative resistances, not only to limit the intensity of Septoria tritici blotch epidemics, but also to reduce the erosion of resistances by managing evolution of the pathogen population at a pluriannual scale.  相似文献   

11.
A multiplex Polymerase Chain Reaction (PCR) assay was developed to detect and quantify four fungal foliar pathogens in wheat. For Septoria tritici (leaf blotch) and Stagonospora nodorum (leaf and glume blotch), the -tubulin gene was used as the target region. Diagnostic targets for Puccinia striiformis (stripe or yellow rust) and P. recondita (brown rust) were obtained from PCR products amplified with -tubulin primer sequences. Final primer sets were designed and selected after being tested against several fungi, and against DNA of infected and healthy wheat leaves. For detection of the four pathogens, PCR products of different sizes were amplified simultaneously, whereas no products were generated from wheat DNA or other non-target fungi tested. The presence of each of the diseases was wheat tissue- and cultivar specific. Using real-time PCR measurements with the fluorescent dye SYBR Green I, PCR-amplified products could be quantified individually, by reference to a standard curve generated by adding known amounts of target DNA. Infection levels for each of the diseases were measured in the flag leaf of 19 cultivars at Growth Stage (GS) 60–64 in both 1998 and 1999. The infection levels for the cultivars were ranked, and showed, with a few exceptions, a good correlation with the NIAB Recommended List for winter wheat, which is based on visual assessment of symptoms. With PCR, the presence of the different pathogens was accurately diagnosed and quantification of pre-symptomatic infection levels was possible. Although sampling and DNA detection methods need further optimisation, the results show that multiplex PCR and quantitative real-time PCR assays can be used in resistance screening to measure the interaction between different pathogens and their hosts at different growth stages, and in specific tissues. This should enable an earlier identification of specific resistance mechanisms in both early-stage breeding material and field trials.  相似文献   

12.
Initial experiment on the reactions of five Japanese cultivars of cucumber toColletotrichum orbiculare infection in the greenhouse revealed that cv Suyo and Gibai were susceptible and moderately susceptible, respectively, while cv Shogoin fushinari and Sagami hanjiro were resistant to infection byC. orbiculare; cv Ochiai fushinari was moderately resistant. The ability of 16 plant growth promoting fungi (some isolates belonged to species ofPhoma and some non-sporulating isolates) isolated from zoysiagrass rhizospheres to induce systemic resistance in the above five cucumber cultivars was tested by growing plants in potting medium infested with barley grain inocula of PGPF in the greenhouse. The second true leaves of 21-day-old plants were challenge inoculated withC. orbiculare and disease assessed. Nine, out of 16 isolates, caused significant reduction of disease caused byC. orbiculare in at least two cultivars.Phoma isolates (GS8-1 and GS8-2) and non-sporulating isolates (GU21-2, GU23-3, and GU24-3) significantly reduced the disease in all the five cultivars. The disease suppression in cucumber was due to the induction of systemic resistance, since the inducer(s) and the pathogen were separated spatially and that the inducer did not colonize aerial portions. The resistance induced by certain isolates in a susceptible cultivar was less than that in a resistant cultivar. Disease suppression caused by isolate GU21-2 was similar to theC. orbiculare induced control in certain cultivars. The average rate of expansion of lesion diameter on leaves due toC. orbiculare was slower due to induction with the selected plant growth promoting fungi compared to the uninduced control plants. Roots of four cultivars were colonized by only three isolates, however, roots of one cultivar (Suyo) was colonized by five isolates suggesting the cultivar-specific root colonization ability.Abbreviations cv cultivar(s) - PGPF plant growth promoting fungal isolates - PGPR plant growth promoting rhizobacteria  相似文献   

13.
For wheat, the optimum time to apply fungicide to control disease on a given leaf layer is usually at, or shortly after, full leaf emergence. Data from field experiments on barley were used to investigate whether the same relationship was applicable to control of leaf blotch on barley. Replicated plots of winter barley were sown in the autumns of 1991, 1992 and 1993 at sites in southwest England with high risk of Rhynchosporium secalis infection. Single fungicide treatments at four doses (0·25, 0·5, 0·75 or 1·0 times the label rate) were applied at one of eight different spray times, starting in mid-March in each year, with intervals of 10–11 days between spray timings. Disease was assessed every 10–11 days and area under the disease progress curve (AUDPC) values were used to construct fungicide dose by spray time response surfaces for each of the upper four leaves, for each year. Spray timings shortly before leaf emergence were found to minimize the AUDPC for each year and leaf layer, and also the effective dose (the dose required to achieve a specified level of control), similar to wheat. Fungicide treatments on barley were effective for a longer period before leaf emergence than afterwards, probably because treatments before emergence of the target leaf reduced inoculum production on leaves below. This partly explains why fungicides tend to be applied earlier in the growth of barley compared with wheat.  相似文献   

14.
A Pyrenophora graminea strain expressing the -glucuronidase gene (GUS) was obtained via genetic transformation, and used to follow the penetration of the pathogen inside barley germinating seeds and the colonization of host tissues. Significant differences between resistant and susceptible barley cultivars were observed in the colonization of artificially-infected embryos by the fungus. These results suggest that the GUS transgenic strain of P. graminea will be useful for the early screening of barley cultivars for resistance to leaf stripe disease.  相似文献   

15.
ABSTRACT A leaf spot disease with unknown etiology has become more pronounced in spring and winter barley in Germany in recent years. The symptoms are similar to net blotch and Ramularia leaf spots, but the causal agents of these diseases are not identified. The symptom expression varied much on cultivars. Cultivars most affected by the disease of both spring and winter barley showed a significantly higher level of superoxide (O(2) ) production and lipid peroxidation (malondialdehyde), but a lower level of antioxidant potential expressed as superoxide dismutase (SOD) activity, catalase activity, and integral water-soluble antioxidant capacity (ACW) than insensitive cultivars. A high positive correlation between O(2) production and leaf spot development between ear emergence and milk ripeness was established in the most sensitive winter barley cv. Anoa (r(2) = 0.9622) and spring barley cv. Barke (r(2) = 0.9434). Leaf H(2)O(2) levels increased with the severity of leaf spots. The histochemical localization of O(2) and H(2)O(2) in the tissues adjacent to leaf spots indicated that these two active oxygen species (AOS) are involved in the formation of leaf spots. Reduction of symptom severity by applying strobilurin and azole fungicides was always associated with elevated SOD activity and ACW content and suppressed O(2) production. However, peroxidase activities were significantly higher in sensitive cultivars and in more severely affected tissues and decreased by applying fungicides. Thus, it is assumed that a possible genetic mechanism based on the imbalanced AOS metabolism contributes to formation of physiological leaf spots.  相似文献   

16.
Fukui R  Fukui H  Alvarez AM 《Phytopathology》1999,89(11):1007-1014
ABSTRACT Effect of temperature on leaf colonization in anthurium blight was studied using a bioluminescent strain of Xanthomonas campestris pv. dieffenbachiae. In a susceptible cultivar, colonization of leaf tissues (monitored by detection of bioluminescence) and symptom development (assessed visually) advanced rapidly at higher temperatures. For a susceptible cultivar, there was a linear relationship between degree-days and percent leaf area colonized by the pathogen, indicating that leaf colonization in a susceptible cultivar was a direct function of the cumulative effect of temperature. The degree-day intercept of the regression line represented the time from inoculation to detection of bioluminescence, and the slope indicated the increase of leaf colonization per degree-day. There also was a linear relationship between the logarithm of degree-days and the logarithm of percent leaf area showing visible symptoms in a susceptible cultivar. The degree-day intercept of this relationship represented the incubation period (about 500 degree-days). The degree-days required to detect bioluminescence was not considerably different between susceptible and resistant cultivars. However, the subsequent rates of leaf colonization were significantly lower for a resistant cultivar than for a susceptible cultivar in all temperature regimes. The results suggest that multiplication of the pathogen in the leaf tissues is optimized in the susceptible cultivar. In contrast, in the resistant cultivar, the defense mechanisms overshadow the temperature effect. The differential response to temperatures may be an additional indicator of cultivar susceptibility.  相似文献   

17.
小麦茎基腐是由多种镰孢菌侵染的世界性土传病害,亚洲镰孢菌(Fusarium asiaticum)是我国冬小麦主产区茎基腐镰孢菌的优势种群,对小麦生产造成巨大损失。本研究利用绿色荧光蛋白报告基因标记亚洲镰孢菌,研究其侵染抗感小麦的病理组织学过程,建立了茎基腐病菌与寄主互作的直观性的研究体系,对病害防治及抗病育种具有重要意义。基于PEG-CaCl_2介导原生质体转化法将gfp导入亚洲镰孢菌株CF0915,对转化子进行荧光表达、PCR验证、遗传稳定性、生长特性及致病力分析,选取与野生型表现相近的转化子进行侵染分析。结果表明,绿色荧光蛋白基因(gfp)与潮霉素基因(hyg)PCR扩增表明gfp已整合入真菌基因组中,转化子菌丝与分生孢子表现强烈绿色荧光信号,gfp能够在转化子中稳定遗传,菌落形态、生长速度及致病力与野生型菌株无显著差异;将gfp标记病菌分生孢子接种感病品种1 d后,大量孢子附着于根毛及根表皮细胞开始萌发,接种2 d后观察到抗性品种分生孢子萌发;感病品种接种3 d后,菌丝直接侵入表皮细胞或沿表皮细胞间层定殖生长,扩展至皮层组织,8 d后菌丝从根部迅速扩展至茎基部,至第10 d大量菌丝充塞根皮层细胞,叶鞘维管束也被菌丝侵染,并产生大量大型分生孢子,植株表现褐色病斑,14 d后根部及茎维管束被大量菌丝体填充,而后产生大量厚垣孢子,至25 d大部分感病品种幼苗萎蔫死亡;与感病品种相比,抗性品种在整个侵染过程中表现时间滞后。本研究对引起茎基腐病的亚洲镰孢菌侵染小麦的组织学过程观察,为病菌致病机理的阐释及抗病资源的利用提供了重要理论依据。  相似文献   

18.
The relative resistance of 15 winter barley, three winter wheat and three winter oat cultivars on the UK recommended list 2003 and two spring wheat cultivars on the Irish 2003 recommended list were evaluated using Microdochium nivale in detached leaf assays to further understand components of partial disease resistance (PDR) and Fusarium head blight (FHB) resistance across cereal species. Barley cultivars showed incubation periods comparable to, and latent periods longer than the most FHB resistant Irish and UK wheat cultivars evaluated. In addition, lesions on barley differed from those on wheat as they were not visibly chlorotic when placed over a light box until sporulation occurred, in contrast to wheat cultivars where chlorosis of the infected area occurred when lesions first developed. The pattern of delayed chlorosis of the infected leaf tissue and longer latent periods indicate that resistances are expressed in barley after the incubation period is observed, and that these temporarily arrest the development of mycelium and sporulation. Incubation periods were longer for oats compared to barley or wheat cultivars. However, oat cultivars differed from both wheat and barley in that mycelial growth was observed before obvious tissue damage was detected under macroscopic examination, indicating tolerance of infection rather than inhibition of pathogen development, and morphology of sporodochia differed, appearing less well developed and being much less abundant. Longer latent periods have previously been related to greater FHB resistance in wheat. The present results suggest the longer latent periods of barley and oat cultivars, than wheat, are likely to play a role in overall FHB resistance if under the same genetic control as PDR components expressed in the head. However the limited range of incubation and latent periods observed within barley and oat cultivars evaluated was in contrast with wheat where incubation and latent periods were shorter and more variable among genotypes. The significance of the various combinations of PDR components detected in the detached leaf assay as components of FHB resistance in each crop requires further investigation, particularly with regard to the apparent tolerance of infection in oats and necrosis in barley, after the incubation period is observed, associated with retardation of mycelial growth and sporulation.  相似文献   

19.
ABSTRACT Pyrenophora teres, the causal agent of net blotch of barley (Hordeum vulgare L.), induces a combination of necrosis and extensive chlorosis in susceptible barley cultivars. Cell-free filtrates from both net and spot forms of P. teres; P. teres f. sp. teres, and P. teres f. sp. maculata were found to contain phytotoxic low molecular weight compounds (LMWCs) and proteinaceous metabolites which appear to be responsible for different components of the symptoms induced by the two forms of the pathogen in a susceptible cultivar of barley (cv. Sloop). Proteins induced only brown necrotic spots or lesions similar to those induced by the pathogens 72 h after inoculation. In contrast, LMWCs induced general chlorosis seen 240 h after inoculation but not the localized necrosis. Neither hydrolyzed or heat- or protease-treated proteinaceous metabolites induced the symptoms. This is the first report of the involvement of proteins produced by P. teres in symptom development during net blotch disease of barley.  相似文献   

20.
A detached seedling leaf technique was developed to screen for resistance to septoria tritici blotch of wheat and to detect specific interactions between cultivars and isolates. Wheat seedlings were inoculated with spore suspensions of Mycosphaerella graminicola . Detached primary leaves were then placed in a clear plastic box such that their cut ends were sandwiched between layers of agar containing benzimidazole, with a gap below the middle of the leaves. Mean levels of disease were affected by light and temperature, and also by the concentration of benzimidazole, such that higher concentrations resulted in less disease. Second leaves were more susceptible than seedling primary leaves. However, none of these factors affected ranking of disease among cultivars or cultivar-by-isolate interactions. Kavkaz–K4500 1.6.a.4, Synthetic 6x and Triticum macha showed specific susceptibility and resistance to different isolates. The detached leaf technique could be a useful complement to field trials and an alternative to whole seedling assays in assessing cultivar resistance and investigating the genetics of the host–pathogen interaction.  相似文献   

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