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1.
An in vitro detached leaf assay, involving the inoculation of detached leaves with Microdochium nivale, was further developed and used to compare with whole plant resistance ratings to Fusarium head blight (FHB) of 22 commercial cultivars and published information on 21 wheat genotypes, identified as potential sources for FHB resistance. An incubation temperature of 10 °C and isolates of M. nivale var. majus of intermediate pathogenicity were found to be the most suitable for the differential expression of several components of partial disease resistance (PDR), namely incubation period, latent period and lesion length, in wheat genotypes used in the detached leaf assay. There were highly significant differences (P < 0.001) for each component of PDR within commercial cultivars and CIMMYT genotypes. Positive correlations were found between incubation period and latent period (r = 0.606; P < 0.001 and r = 0.498; P < 0.001, respectively, for commercial cultivars and CIMMYT genotypes), inverse correlations between incubation period and lesion length (r = -0.466; P < 0.01 and r = –0.685; P < 0.001, respectively) and latent period and lesion length (r = –0.825; P < 0.001 and r = –0.848; P < 0.001, respectively). Spearman rank correlations between individual PDR components and UK 2003 recommended list ratings were significant for incubation period (rs = 0.53; P < 0.05) and latent period (rs = 0.70; P < 0.01) but not for lesion length (r s = –0.26). Commercial cultivars identified with high resistances across all three PDR components in the detached leaf assay also had high whole plant FHB resistance ratings, with the exception of cv. Tanker which is more susceptible than the results of the detached leaf assay suggested, indicating an additional susceptibility factor could be present. Agreement between resistances found in the detached leaf assay and resistance to FHB suggests resistances detected in detached leaves are under the same genetic control as much of the resistances expressed in the wheat head of the commercial cultivars evaluated. In contrast, high resistances in each of the PDR components were associated with higher susceptibility across 19 CIMMYT genotypes previously evaluated as potential breeding sources of FHB resistance (incubation period: r = 0.52; P < 0.01, latent period: r = 0.53; P < 0.01, lesion length: r = –0.49; P < 0.01). In particular, the CIMMYT genotypes E2 and E12 together with Summai #3, known to have high levels of whole plant FHB resistance, showed low levels of resistance in each PDR component in the detached leaf assay. Such whole plant resistances, which are highly effective and not detected by the detached leaf assay, do not appear to be present in Irish and UK commercial cultivars. The most resistant Irish and UK commercial cultivars were comparable to the genotype Frontana and the most resistant CIMMYT germplasm evaluated in the leaf assay.  相似文献   

2.
Experiments over five growing seasons at Rothamsted (1998/99–2002/03), four seasons at Boxworth (1998/99, 1999/2000, 2001/02, 2002/03) in England (Leptosphaeria maculans) and three seasons (1998/99–2000/01) at Poznan in Poland (Leptosphaeria biglobosa) suggest that differences in the development of phoma stem canker epidemics between England and Poland relate to differences in weather patterns between the two countries. The duration of ascospore release was longer in England, where winter weather is mild and wet, than in Poland, where winters are cold and often with snow cover, but there was little difference between two sites in England (Rothamsted and Boxworth). Wetness provided by rainfall was essential for release of ascospores of both L. maculans in England and L. biglobosa in Poland. Temperature did not affect release of ascospores over the range 5–20 °C. Diurnal periodicity in release of ascospores of L. maculans in England and L. biglobosa in Poland was similar. The timing (date) of first release of ascospores of L. maculans or L. biglobosa in autumn was related to rainfall in August and September; with increasing rainfall the date was earlier. The incubation periods from first release of ascospores to first appearance of phoma leaf spots for both L. maculans in England and L. biglobosa in Poland, and from first leaf spots to first stem base canker in England, were described using a thermal time (degree-day) approximation.  相似文献   

3.
Foliar sprays and soil drenches with DL--amino-n-butyric acid (BABA) reduced the number of Heterodera avenae and H. latipons cysts on wheat and barley. Foliar sprays of wheat with 8000mgl–1 BABA reduced the number of H. avenae cysts by 90%, whereas 2000mgl–1 BABA was enough to reduce the number of H. latipons cysts by 79%. Multiple spray treatments with 2000mgl–1 BABA at 10-day intervals reduced the number of H. avenae cysts on wheat and barley. A soil drench of wheat with 125mgl–1 BABA reduced the number of H. latipons cysts by 93% and H. avenae cysts by 43%. Second-stage juveniles of these nematodes penetrated and formed syncytia in wheat roots soil-drenched with BABA. More adult males of H. avenae were produced in BABA (<250mg1–1)-treated wheat roots (~76%) than in untreated roots (27%). Soil drenches with higher concentrations of BABA inhibited development of adult males and females. Several chemical elicitors of induced resistance were tested for their ability to reduce the number of H. avenae cysts on wheat. Only BABA was found to be an effective resistance inducer. The number of egg masses of an unidentified Meloidogyne sp. root-knot nematode, which infects only monocots, was also reduced by 95% by a soil drench of wheat with 500mgl–1 BABA. Development of this nematode inside the BABA-treated roots was also inhibited.  相似文献   

4.
An aphid and virus survey was conducted from 1993 and 1999 on the eastern lowlands in Hungary. Aphid flight was monitored with two yellow pan traps placed on the edge and in the middle of seed potato fields. From 1993 and 1997, aphid flight was monitored with a Rothamsted type suction trap. The aphid and virus survey was continued in four different regions of Hungary in 2000. Aphid flight activity recorded by the suction trap and the yellow pan traps was different. Cumulative vector intensity based on yellow pan trap catches revealed a greater variation between years than among the different locations. In 4years out of 8, aphid flight was less intensive and quality seed potato was harvested regardless of the production site. Cumulative vector intensity is a good means to forecast the time of haulm destruction in seed potatoes.  相似文献   

5.
Mature green mango fruits of commercially important varieties were screened to investigate the levels of constitutive antifungal compounds in peel and to assess anthracnose disease after inoculation with Colletotrichum gloeosporioides. High-pressure liquid chromatography was used to quantify the levels of 5-n-heptadecenylresorcinol and 5-n-pentadecylresorcinol in the peel extracts. The fruit peel of the varieties ‘Kensington Pride’ and ‘Keitt’ were observed to have the highest levels of both 5-n-heptadecenylresorcinol (107.3–123.7 and 49.9–61.4 μg/g FW, respectively) and 5-n-pentadecylresorcinol (6.32–7.99 and 3.30–6.05 μg/g FW, respectively), and the fruits of the two varieties were found to have some resistance to postharvest anthracnose. The varieties ‘Kent’, ‘R2E2’, ‘Nam Doc Mai’, ‘Calypso’ and ‘Honey Gold’ contained much lower concentrations of resorcinols in their peel and three of these varieties were found to be more susceptible to anthracnose. Concentrations of 5-n-heptadecenylresorcinol were significantly lower at the ‘sprung’ and ‘eating ripe’ stages of ripening compared to levels at harvest. Concentrations of 5-n-pentadecylresorcinol did not differ significantly across the three stages of ripening. The levels of these two resorcinols were found to be strongly inter-correlated (P<0.01, r2=0.71), with concentrations of 5-n-heptadecenylresorcinol being an average 18 times higher than those of 5-n-pentadecylresorcinol. At the ‘eating ripe’ stage, significant relationships were observed between the concentrations of each type of alk(en)ylresorcinol and anthracnose lesion areas following postharvest inoculation, P<0.001, r2= 0.69 for 5-n-pentadecylresorcinol, and P<0.001, r2= 0.44 for 5-n-heptadecenylresorcinol.  相似文献   

6.
In controlled near-optimum conditions (18 °C), monocyclic sporulation capacity and spore infection efficiency were assessed for faba bean rust on the first and second leaves of field bean. After a latency period of 8–10 days, lesions sporulated duringc. 50 days. Spore production on the second leaf,c. 9×104 spores per lesion, was two times as high as spore production on the first leaf. Infection efficiency was similar for both leaf layers, with a mean value of 0.11 lesion per inoculated spore. Infection efficiency decreased strongly when spores originated from mother lesions older than 20 days. Three life-table statistics (the net reproduction numberR o , the mean generation timeT g , and the maximum relative growth rater max ) were calculated.R o was larger andT g was longer for the second than for the first leaf, butr max was nearly the same for both leaf layers (0.31–0.33 day–1).r max was compared with the exponential growth rater measured in a field experiment. From the difference between the two rates, the fraction of inoculum lost in field conditions was estimated at 0.54–0.94. The life-table statistics were also compared to those of other legume rusts, and implications of life-table analysis for comparative epidemiology were discussed.  相似文献   

7.
为了明确Cd与Zn复合胁迫对麦长管蚜Sitobion avenae(Fabricius)生长发育与繁殖的影响,在室内采用不同含量Cd~(2+)与Zn~(2+)溶液交互处理土壤-小麦-麦长管蚜系统,利用特定年龄生命表研究在不同含量Cd与Zn复合胁迫下麦长管蚜生命参数及繁殖的变化规律。结果表明,Cd、Zn以及Cd与Zn交互作用均极显著影响麦长管蚜的生命参数与繁殖,其中Zn对麦长管蚜种群参数的影响最大。在40 mg/kg Cd与400 mg/kg Zn复合胁迫下,麦长管蚜种群的内禀增长率、净增值率显著高于单一Cd胁迫;但不同含量Cd与800、1 600 mg/kg高含量Zn或不同含量的Zn与120、240 mg/kg高含量Cd复合胁迫时,其内禀增长率与净增值率却逐渐下降;其平均世代周期在复合胁迫条件下显著低于单一Cd胁迫。生殖力曲线面积的变化规律与种群参数的变化规律相同,推测40 mg/kg和400 mg/kg分别为Cd与Zn复合胁迫的关键含量。研究表明,低含量Cd与Zn复合胁迫能显著促进麦长管蚜生长发育,而高含量Cd与Zn复合胁迫并不能促进麦长管蚜的生长发育。  相似文献   

8.
The epidemiology ofMetopolophium dirhodum and its natural enemies on winter wheat was studied from 1975 to 1979 inclusive. AlateM. dirhodum colonize wheat from the middle of May onwards. Immigration occurs until mid-June. Population growth rates ofM. dirhodum can be as high as or occasionally even higher than those ofSitobion avenae. InM. dirhodum alatae are formed in a high proportion throughout the epidemic whereas inS. avenae the % of alatae becomes high at the end. In both species most of these alatae seem to emigrate. Both species have a similar potential to become a pest.Samenvatting De epidemiologie vanMetopolophium dirhodum werd bestudeerd van 1975–1989 en vergeleken met die vanSitobion avenae. Beide soorten migreren naar tarwe in de loop van mei. De relatieve populatie groeisnelheid vanM. dirhodum bleek tijdelijk zeer hoog te zijn (verdubbelingstijd 1,7 dag tegenover 2,0 voorS. avenae). Over de gehele periode van de epidemie is er weinig verschil in dagelijkse relatieve groeisnelheid van de populatie.Bij de ineenstorting, die altijd begint voor het deegrijpstadium van de tarwe, is van belang het ontstaan van gevleugelde bladluizen. Deze verlaten merendeels het gewas. Het belang van de natuurlijke vijanden voor de afname van de populatie is niet altijd duidelijk maar is soms groot en veroorzaakt dan een vroege ineenstorting van de plaag. M. dirhodum heeft even grote mogelijkheden de plaagstatus te bereiken alsS. avenae maar door zijn soms tijdelijk groter vermeerderingsvermogen zal het voorspellen moeilijker zijn.  相似文献   

9.
A dynamic, process-based simulation model is used to evaluate the effect of injury bySitobion avenae F. on yield of winter wheat at a range of attainable yield levels. The attainable yield is defined as the yield in the absence of pests and diseases, at the prevailing temperature and radiation and the available amount of soil nitrogen. Water limitation is not taken into account. Only the period from flowering to ripeness is considered. Aphid infestation intensity is expressed in aphid-days, the integral of aphid density (tiller–1) over time (day). The calculations show that damage per aphid-day decreases from flowering to ripeness because damage caused by honey-dew decreases with advancing crop development stage while damage caused by aphid feeding is about constant. Damage per aphid-day during a particular period of crop development increases in a nearly linear fashion with the attainable yield level. At attainable yield levels over approximately 9000 kg ha–1 and until crop development stage early milky ripe (DC 73), however, damage per aphid-day increases at a higher rate with the attainable yield level as compared to lower yield levels. The crop-physiological causes are discussed.Regression models are constructed that relate simulated aphid damage both during various periods of crop development and averaged over the entire post-anthesis phase, to the simulated attainable yield level. The accuracy of these simulation-based regression models and five published models of damage in winter wheat caused byS. avenae is evaluated using 21 data sets, obtained in experiments carried out between 1973 and 1984 in the Netherlands. Attention is focussed on two aspects of model accuracy: the agreement between predicted and measured damage and the size of the error in model predictions. In both aspects the simulation-based regression models are as good as the best published empirical models.  相似文献   

10.
The network of suction traps operated by the Rothamsted Insect Survey has provided records of aphid activity since 1965. Previous attempts to use this information with meteorological data for predicting aphid problems have concentrated mainly on simple linear regression techniques. In this paper the value of a more complex multiple regression approach is investigated using additional data from an increased range of sites, species and years. Data from 1966 to 1988 are used to produce models to predict the date of the first record of each of 49 aphid species at each of six sites. The models used were particularly successful in predicting the date of the first record at a range of sites in 1989 of four species: Myzus persicae, Macrosiphum euphorbiae, Sitobion avenae and Phorodon humuli.  相似文献   

11.
Coniothyrium minitans grew on all ten solid-substrates (barley, barley-rye-sunflower, bran-vermiculite, bran-sand, maizemed-perlite, millet, oats, peat-bran, rice and wheat) tested, producing high numbers of germinable pycnidiospores (1.9–9.3×108 g–1 air dry inocula). All solid substrate inocula survived better in the laboratory at 5 and 15 °C than at 30 °C for at least 64 weeks.In pot bioassays carried out in the glasshouse and field, soil incorporations of each inoculum almost completely inhibited carpogenic germination ofS. sclerotiorum. In the field bioassay, no sclerotia were recovered after 38 weeks fromC. minitans-treated pots compared to 56% from control pots. In the glasshouse bioassay, 9–30% of sclerotia were recovered after 20 weeks fromC. minitans-treated pots, but 88–100% of these were infected by the antagonist. The antagonist also spread to infect sclerotia in control pots.In larger scale glasshouse trials, single preplanting soil-incorporations of five inocula (barley-ryesunflower, maizemeal-perlite, peat-bran, rice and wheat) controlled Sclerotinia disease in a sequence of lettuce crops, with only small differences between the types of inocula tested. At harvest,C. minitans reduced sclerotial populations on the soil surface and over 74% of sclerotia recovered fromC. minitans-treated plots were infected by the antagonist.C. minitans survived in soil in all solid-substrate inocula-treated plots for at least 39 weeks at levels of 104–105 colony forming units cm–3 soil and spread to infect over 36% of sclerotia recovered from control plots.  相似文献   

12.
Black pod, caused by Phytophthora spp. is one of the most important diseases of cacao occurring worldwide. Losses due to black pod caused by P. palmivora are still moderate in Côte d'Ivoire but P. megakarya causes high losses in Ghana and other Central African countries. Variation in field attack has been observed between cacao genotypes, but evaluation of pod losses is unsuitable for obtaining rapid progress in breeding. Results of inoculation tests using young detached leaves, twigs and roots, obtained from field and nursery plants, are presented here and compared to field resistance of similar genotypes observed over a 10-year period. Nine different Upper Amazon Forastero genotypes were tested together with progenies obtained by crossing these with the susceptible check IFC5 (Amelonado genotype). Rank correlations between the early screening tests and the level of field attack were positive and mostly significant (r=0.58–0.95). The coefficient of correlation was slightly higher for leaves (r=0.88) and roots (r=0.89) than for twigs (r=0.76). Also, resistance of the different plant organs was correlated (r=0.6–0.9). Resistance of the Upper Amazon parents was well correlated with the resistance of their cross progenies (r=0.7–0.9), suggesting that resistance is highly heritable. Resistance of leaves and twigs from the nursery was better correlated with field resistance than resistance of leaves and twigs from the field, which might result from more uniform growing conditions in the nursery. Inoculation of leaves appears the most suitable early screening method for black pod resistance. Application of this test in breeding more resistant cacao cultivars is discussed.  相似文献   

13.
The study extending over all sixteen counties of Hungary has shown atrazine resistant biotypes of Amaranthus retroflexus L. to grow not only in and around maize monocultures but also in rotationally grown maize and even along highways and ruderal areas. In the present study made in 1983 resistant A. retroflexus was found in five counties (Bács-Kiskun, Csongrád, Hajdu-Bihar, Nógrád and Szabolcs-Szatmár) where Hartmann recorded it as absent in 1976. In addition, resistant populations were also found in the counties of Szolnok and Veszprém. The area in which populations of A. retroflexus have developed resistance to atrazine therefore appears to be extending.  相似文献   

14.
D. HORNBY 《EPPO Bulletin》1987,17(4):615-623
In seeking biological control of the wheat take-all fungus (Gaeumannomyces graminis var. tritici) by introduced organisms, the demonstration of satisfactory field performance is proving a formidable hurdle. A novel experimental design incorporating small plots, 37 x 31 cm, has been used in UK at Rothamsted and Woburn since 1983 to test different kinds of control for take-all and to explore some of the problems of providing adequate field tests of putative biocontrol agents. Three years of bacterial treatments, using different plots each year, provided no evidence of effective control of the disease. Of the few significant treatment effects, most occurred in spring and were temporary: at Woburn they were mostly decreases in take-all and at Rothamsted mostly decreases in growth of the wheat plant without concomitant changes in take-all.  相似文献   

15.
An aphid and virus survey was conducted from 1993 and 1999 on the eastern lowlands in Hungary. Aphid flight was monitored with two yellow pan traps placed on the edge and in the middle of seed potato fields. From 1993 and 1997, aphid flight was monitored with a Rothamsted type suction trap. The aphid and virus survey was continued in four different regions of Hungary in 2000. Aphid flight activity recorded by the suction trap and the yellow pan traps was different. Cumulative vector intensity based on yellow pan trap catches revealed a greater variation between years than among the different locations. In 4years out of 8, aphid flight was less intensive and quality seed potato was harvested regardless of the production site. Cumulative vector intensity is a good means to forecast the time of haulm destruction in seed potatoes.  相似文献   

16.
The relationships between yield loss and incidence (% plants with stems affected) or severity (mean stem score, 0–4 scale) of stem canker in winter oilseed rape were analysed using data from experiments at Rothamsted in 1991/92, Withington in 1992/93, Boxworth in 1993/94 and Rothamsted in 1997/98. Critical point models and area under disease progress curve (AUDPC) models were better than multiple point models for describing relationships between yield (tha–1) and incidence or severity of stem canker for the four experiments. Since yield is influenced by many factors other than disease, % yield loss was calculated and critical point models and AUDPC models relating % yield loss to stem canker were constructed. The critical point models for % yield loss on stem canker incidence for three of the four experiments were similar, but differed from that for Rothamsted in 1991/92. There were also no differences between models of % yield loss on AUDPC of both incidence and severity for these three experiments. Therefore, general models of % yield loss (L) against AUDPC of incidence (X) or severity (S) of stem canker from growth stages 4.8 to 6.4 were derived from the combined data sets for the three experiments: L=–0.76+0.0075X (R2=35%, p<0.001), L=0.26+0.53S (R2=37%, p<0.001). The relationships between % yield loss and % plants with different stem canker severity scores at different growth stages were also analysed; the greatest yield losses were generally associated with the largest severity scores, for plants assessed at the same crop growth stage, and were also associated with the early development of stem lesions. Further analyses showed that % yield loss was related to incidence or severity of both basal stem cankers and upper stem lesions in experiments at Boxworth in 1993/94 and at Rothamsted in 1997/98.  相似文献   

17.
The survival of the bacterial pathogen, Xanthomonas campestris pv. campestris (Xcc), was studied in plant debris-infested soil with different matric potentials (0, –10, –30, –50, –100, –200, and –900kPa), and on the phylloplane of crops used for rotation with cabbage. Populations of cellulolytic and proteolytic microorganisms were studied in relation to soil matric potential and Xcc. The survival of Xcc was negatively correlated (r=–0.710; P=0.06) with soil matric potential and with the abundance of cellulolytic microorganisms (P=0.05). In saturated soil, Xcc survived for only 19–28 days, while at –900kPa there was no significant change in the bacterial population within this period. Survival of Xcc on the phylloplane of cabbage (Brassica oleracea var. capitata) (host) was similar to that on mustard and lettuce (48 days), whereas the pathogen was detected for only 9 days on rice. It appears that high matric potentials reduced populations of Xcc in soil, whereas epiphytic survival of this pathogen depended on the plant species.  相似文献   

18.
The aphid‐transmitted viruses Potato virus Y (PVY) and Potato virus A (PVA) commonly affect seed potatoes in the UK. The transmission efficiency for aphid species is used to calculate a potential transmission risk and is expressed as a relative efficiency factor (REF). These REFs have not previously been calculated for UK strains of viruses or aphid clones. Using a previously published method, REFs have been calculated for the aphid species and viruses commonly occurring in UK potatoes. The efficiency of transmission of Myzus persicae is nominally set to a REF of 1 and REFs for other species are calculated relative to this. These data represent the first set of REFs calculated for PVA transmission. Macrosiphum euphorbiae (REF 0.91) was almost as efficient as M. persicae at PVA transmission. The data were further analysed to compare transmission rates of PVY and PVA using a binomial (logit) generalized mixed model to take into account the potential influence of variation in virus titre between leaves. This approach found that there is little variation between the efficiency of transmission between clones of each aphid species or between strains within a virus species. This is a first report that Aphis fabae, Metopolophium dirhodum, Sitobion avenae, Acyrthosiphon pisum and Cavariella aegopodii have the ability to vector PVA. This study also represents a first report that C. aegopodii has the ability to vector PVY and confirms the potential of S. avenae, A. fabae, M. euphorbiae and Rhopalosiphum padi as important PVY vectors.  相似文献   

19.
A significant increase in the occurrence of red stripe (caused by Acidovorax avenae subsp. avenae) has been observed in the last decade in Argentina. Considering that no extensive sampling of the main sugarcane-producing area in the country has been conducted to characterize the diversity and population structure of A. avenae subsp. avenae, molecular markers were employed to analyse 112 isolates from Tucumán. By using repetitive element polymorphism-based polymerase chain reaction (rep-PCR) almost all isolates were differentiated and grouped into 10 clusters, revealing a high genetic diversity. Using the amplified fragment length polymorphism (AFLP) technique, five pairs of isolates were discriminated that could not be distinguished with rep-PCR. Cluster analysis showed no clear association between isolate clustering, sugarcane host genotype, crop age, type of tissue sampled, fertilization, or year of sampling. Linkage equilibrium analysis by using rep-PCR data indicated that the population has some degree of clonality. Three housekeeping genes were also sequenced: ugpB and pilT sequences were highly similar to A. avenae subsp. avenae sequences from other Argentinian isolates, whereas the lepA sequence did not reveal significant similarity. An additional four housekeeping genes could not be amplified, suggesting the existence of differences in those regions. Subsequently, virulence of 14 A. avenae subsp. avenae isolates was evaluated under controlled conditions. Results showed a differential level of aggressiveness among the isolates on a resistant sugarcane variety. This study confirmed that rep-PCR is an adequate tool for genetic analysis and population structure characterization in bacteria, and revealed both high genetic diversity and clonal population structure of A. avenae subsp. avenae in Tucumán, Argentina.  相似文献   

20.
Bt-maize crop is increasingly used worldwide and the study of ecological side effects is a major subject in this domain. Under laboratory conditions, we determined Bt-maize effects on the non-target aphid Sitobion avenae (Fabricius) (Homoptera: Aphididae). We found no significant differences between S. avenae on MON810 and the near-isogenic line when alate offspring production, apterous survivorship, longevity, intrinsic rates of natural increase (rm), finite rates of increase and doubling times were compared. No significant differences were found between treatments for apterous pre-reproductive and reproductive periods. Additionally, we used immunological tests (ELISA) to detect Cry1Ab protein in maize leaves and S. avenae nymphs. Results showed that Bt-maize leaves expressed 0.203 (±0.05) μg Cry1Ab/g leaf tissue (Mean ± SEM). No Cry1Ab protein was present in S. avenae nymphs developing on Bt or conventional maize. We conclude that Bt-maize does not affect the development of the non-target aphid S. avenae and that Cry1Ab toxin quantities in these aphids are nil, suggesting an inconsequential risk for natural enemies of this aphid species.  相似文献   

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