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1.
Cultivar disease resistance ratings to nodorum blotch (caused by Parastagonospora nodorum) provide critical information to growers to assist with disease management. However, less has been done in terms of yield losses from diseases under different cultivar resistance scenarios. The purpose of this study was to characterize yield and quality loss responses to wheat nodorum blotch as influenced by variety partial resistance, epidemic intensity, and environment. The trial series includes four site/years in Western Australia. Five varieties, Magenta, Calingiri, Trojan, Janz, and Scout were used for all four trials. These varieties represented resistant/susceptible categories MRMS, MS, MSS, S, and SVS, respectively, and were selected on the basis that they were adapted to the western region, had similar maturities, and were resistant to diseases that were potential contaminants. Trials were sown in a strip-plot design with three replicates and five disease levels, with intersecting main-plots of varieties and disease levels, which facilitated comparisons across disease levels within varieties. Current categories of resistance were well reflected in yield and quality responses. A negative exponential relationship was observed between yield and disease, with a nonlinear yield loss function for both flag leaf and glume infection. This indicates that yield is most affected during early stages of disease on flag leaves and glumes. The functional form of yield loss response over four site years was similar among varieties, but varieties differed in their extent of disease expression. Partial resistance in commercial wheat varieties reduced yield loss by 40%–60% of losses observed in susceptible varieties.  相似文献   

2.
A field study is described which explored the possibility of controlling Stagonospora nodorum and Septoria tritici on wheat using a barley pathogen, Drechslera teres. Pre-treatment of wheat cv. Hussar flag leaves with D. teres resulted in a significant reduction in disease caused by S. nodorum and S. tritici, resulting in a significant increase in grain yield. When cv. Brigadier leaves were treated with D. teres prior to inoculation with S. nodorum there was an initial increase in disease expression whilst D. teres had no effect on symptoms produced by S. tritici on cv. Brigadier. There was significantly less disease on leaves of cvs. Hussar and Brigadier pre-treated with D. teres prior to inoculation with an equal mixture of S. nodorum and S. tritici compared to plants pre-treated with water. It is concluded that D. teres and other non-host pathogens show potential as biological control agents for S. nodorum and S. tritici.  相似文献   

3.
The fungal communities on wheat leaves showing symptoms similar to stagonospora nodorum blotch were analysed using terminal restriction fragment length polymorphism (T-RFLP). Collection of diseased leaves was carried out in eleven winter wheat fields located in three regions of Sweden during mid-July in 2003–2005. Fourteen different fungal species were found on the leaves out of which thirteen were identified to the species level and one to the genus level. The majority of the samples had between one and four species present of which at least one was a pathogen. Among the analysed leaves three major leaf pathogens were found: Phaeosphaeria nodorum was common during 2003 and 2004, Mycosphaerella graminicola dominated during 2005. Pyrenophora tritici-repentis was present in all fields, but sometimes in just a few samples. Phaeosphaeria nodorum and P. tritici-repentis often co-occurred on the same leaf. In addition, seven species of yeast and three saprophytes frequently occurred on the leaves every year. The variation in fungal community was largest between the different years while the region of Uppland diverged from the other two regions in species composition. No significant differences in fungal communities were found within a single field, indicating a uniform community at the lowest spatial level.  相似文献   

4.
Tan spot, caused by Pyrenophora tritici-repentis, is a common disease of wheat (Triticum aestivum) responsible for economic losses in some wheat growing areas worldwide. In this study the pathogenic and genetic diversity of 51 P. tritici-repentis isolates collected from different ecological regions of Argentina were analyzed. Virulence tests were conducted on 10 selected wheat cultivars: Buck Halcón, Chris, Gabo, Glenlea, Klein Dragón, Klein Sendero, Max, ND 495, ProInta Guazú and ProInta Imperial. Data revealed significant differences between all main factors evaluated and the interactions for 19 of the isolates analyzed. Based on the reaction type of each isolate/cultivar combination, 48 different pathogenic patterns were detected. The molecular analysis using Inter-Simple Sequence Repeats (ISSR) revealed the existence of 36 different haplotypes among 37 isolates of P. tritici-repentis originally selected for this study. These results indicate that P. tritici-repentis on wheat in Argentina is a heterogeneous fungus, implying that screening wheat germoplasm for resistance for tan spot disease requires a wide range of pathogen isolates.  相似文献   

5.
A method is presented to quantify the net effect of disease management on greenhouse gas (GHG) emissions per hectare of crop and per tonne of crop produce (grain, animal feed, flour or bioethanol). Calculations were based on experimental and survey data representative of UK wheat production during the period 2004–06. Elite wheat cultivars, with contrasting yields and levels of disease resistance, were compared. Across cultivars, fungicides increased yields by an average of 1·78 t ha?1 and GHG emissions were reduced from 386 to 327 kg CO2 eq. t?1 grain. The amount by which fungicides increased yield – and hence reduced emissions per tonne – was negatively correlated with cultivar resistance to septoria leaf blotch (Mycosphaerella graminicola, anamorph Septoria tritici). GHG emissions of treated cultivars were always less than those of untreated cultivars. Without fungicide use, an additional 0·93 Mt CO2 eq. would be emitted to maintain annual UK grain production at 15 Mt, if the additional land required for wheat production displaced other UK arable crops/set aside. The GHG cost would be much greater if grassland or natural vegetation were displaced. These additional emissions would be reduced substantially if cultivars had more effective septoria leaf blotch resistance. The GHGs associated with UK fungicide use were calculated to be 0·06 Mt CO2 eq. per annum. It was estimated that if it were possible to eliminate diseases completely by increasing disease resistance without any yield penalty and/or developing better fungicides, emissions could theoretically be reduced further to 313 kg CO2 eq. t?1 grain.  相似文献   

6.
The Epidemiology of Purple Leaf Blotch on Leeks in Victoria, Australia   总被引：1，自引：0，他引：1  
The incidence of purple leaf blotch disease was investigated on seven successive commercial leek crops grown at Cranbourne, Victoria between 1996 and 1997. First symptoms occurred on older leaves, 54–69 days after transplanting. Lesions with typical symptoms were colonised by either Alternaria porri (6%), Stemphylium vesicarium (42%) or mixtures of both pathogens (52%). Purple leaf blotch was caused by a disease complex and was endemic at nobreak Cranbourne due to the continuous cropping of leeks. Disease incidence in all monitored crops increased as plants matured (123–158 days after transplanting) until harvest but never exceeded 11% due to fortnightly applications of mancozeb. Disease levels showed no significant correlation with weekly temperature, precipitation, relative humidity or leaf wetness duration. Disease levels were significantly (P < 0.05) higher on autumn/winter (May/June) 1997 crops when 38 periods of leaf wetness 8 h because of dew and low temperatures (10–13 °C). The weekly rate of increase of disease incidence was significantly (P < 0.01) correlated with days after transplantation. nobreak Concentrations of airborne A. porri and S. vesicarium conidia within leek crops showed a diurnal periodicity and maximum numbers were trapped between 11:00 and 15:00 h. The concentration of airborne S. vesicarium conidia was three to six times the concentration of airborne A. porri conidia. Conidia were more abundant during spring/summer (September–February). Ascospores of Pleospora allii were found during May–September. The greater concentrations of airborne S. vesicarium conidia suggest that it may be the dominant pathogen in the purple leaf blight complex. Fungicide sprays were unnecessary until 8–10 weeks after transplanting, and regular protectant sprays curtailed but did not eradicate purple leaf blight. The results indicated that predictive models, based on temperature and the frequency of leaf wetness periods 8 h, will assist in reducing fungicide inputs as plants mature and, in southern Victoria, fungicide applications on leeks should be timed for autumn/winter when infection periods occur.  相似文献   

7.
Soybean cultivar Samsoy 1, and the breeding lines TGx 849-313D and TGx 996-26E, grown in a field with a heavy epidemic of frogeye leaf spot caused byCercospora sojina, were treated with double foliar applications of the fungicide benomyl. The treatments were made using four application schedules at six different growth stages, starting from V3 (fully developed leaves, beginning with trifoliate nodes) to R5 (beginning seed_, to determine the effect of the fungucide timing on frogeye leaf spot severity, soybean grain yield and grain quality. Generally, applications at R1 (beginning bloom) and R3 (beginning pod) significantly (P<-0.05) reduced disease severity in the 2 susceptible genotypes, Samsoy 1 and TGx 849-313D. Plot yields of these genotypes were also significantly greater than the untreated controls when the fungicide applications were made at R1 and R3. There was no significant difference in diseave severity or grain yield, between the untreated control and the different times of application, on the resistant genotype TGx 996-26E. Improved seed germination and lower levels of seed infection byC. sojina occurred for all fungicide timings in the susceptible genotypes. The results suggest that fungicide spraying initiated at R1 and followed up at R3 is most effective in frogeye leaf spot control and can also result in higher grain yields, than applications made earlier or later in the season. Control of frogeye leaf spot, however, is best achieved by growing resistant cultivars.  相似文献   

8.
Three field experiments were carried out with the bean cultivar Carioca Comum to investigate the relationships among visual and virtual severity of angular leaf spot (caused by Phaeoisariopsis griseola), area under visual and virtual disease progress curves (AUDPC), healthy leaf area index on any given day (HLAI), healthy leaf area duration (HAD), healthy leaf area absorption (HAA), effective leaf area duration (ELAD), effective leaf area absorption (ELAA) and yield of Phaseolus vulgaris. To obtain a wide range of disease severities, the plots were sprayed with fungicide at different stages of plant growth (before, during and after flowering). Visual and virtual severity and AUDPC showed no significant correlation with yield. However, HAD, HAA, ELAD and ELAA were significantly correlated with yield. Variables that considered the effective leaf area (ELAD and ELAA) provided similar or better coefficients of determination (R2) than those that considered the remaining green leaf area only (HAD and HAA). Single-point models with HLAI, effective leaf area index (ELAI), intercepted radiation by healthy leaf area (HRI) and intercepted radiation by effective leaf area (EHRI) to estimate yield at various times during the crop season were developed. The slope of the relationship between yield and HLAI, ELAI, HRI and EHRI proved to be stable, regardless of planting date and bean growth stage (from R6 to R8).  相似文献   

9.
Fungicides applied at different growth stages were compared for the control of wheat glume blotch, caused by Septoria nodorum (Berk.) Berk. In glasshouse and small-scale field tests, 11 commercially used fungicides, when applied to fully emerged wheat ears, cv. Hobbit, gave only partial control of ear infection by spores applied immediately after spraying. They gave better control of infection of leaves by a similar inoculum. Larger field trials, moreover, indicated better foliar and ear disease control from fungicide applications made before ear emergence, compared with those applied later. In another field trial, nine fungicides were applied to replicated plots of winter wheat, cultivars Atou and Hobbit at GS 31, GS 39, GS 55 or GS 71. On five occasions from anthesis (25 June) until 30 July disease was assessed and green leaf area measured. The trial was harvested on 22 August 1980. Significantly greater yields and grain weights were obtained from plots sprayed with fungicide at GS 39 than from those sprayed at any other time or left unsprayed. Treatments made before symptoms of infection by S. nodorum developed (i.e. before GS 55) prolonged the duration of green leaf areas during the post-anthesis period. Grain weight and yield increases were related closely to the duration of green leaf area above 75 96, but not to the amount of green leaf area at any single assessment nor to the subsequent degree of disease development. The data on which this abstract is based form part of a continuing research programme, the results of which will be published in full at a later date. Full details on the 1980 results referred to above appear in the Annual Report of Long Ashton Research Station (1980).  相似文献   

10.
Interactions between Stagonospora nodorum and Septoria tritici were studied. Results from a detached glume experiment indicated that the interaction may be isolate-dependent, as it was shown that the interaction between the two pathogens may be beneficial or antagonistic depending on the isolate of each pathogen present. The number of spores produced by both pathogens was significantly greater when an aggressive isolate of S. tritici was mixed with a non-aggressive isolate of S. nodorum, whereas the number of spores produced by both pathogens was significantly less when two non-aggressive isolates were mixed. There was a significant reduction in disease level when S. tritici was applied prior to S. nodorum, compared to vice versa in the growth chamber. Results from growth chamber and field studies showed that S. nodorum produced significantly more spores when both pathogens were present together. It is concluded that S. tritici has a stimulatory effect on spore production by S. nodorum. However, there was a reduction of S. tritici spores observed in the dual inoculation treatments, suggesting that S. nodorum inhibits S. tritici.  相似文献   

11.
Field trials were conducted over two seasons to evaluate the efficacy of a water extract of garlic either alone, or in combination with reduced quantities of Benlate (benomyl 50% a.i., WP), for control of brown blotch of bambara groundnut caused byColletotrichum capsici. Results obtained showed that garlic extract has potential for control of brown blotch under field conditions, although it is not so effective as benomyl. Combining the extract with lower dosages of benomyl, however, appeared to have a synergistic effect. Consequently, the treatment comprising half the recommended dosage of benomyl (0.3 gl −1) combined with 1% (w/v) garlic extract was as effective as the full dosage of the fungicide which gave complete control of the disease. http://www.phytoparasitica.org posting Feb. 2, 2003.  相似文献   

12.
In South Asia, foliar blight of wheat (Triticum aestivum L.) is a disease complex caused by Cochliobolus sativus (the spot blotch pathogen) and Pyrenophora tritici-repentis (the tan spot pathogen) which can reduce yields by >30?%. Little is known about the effects of wheat genotypes and their planting time on foliar blight epidemics. Field experiments were conducted to determine the infection potential and epidemic development of C. sativus and P. tritici-repentis on two susceptible (Sonalika and BL1473) and two tolerant (NL750 and Milan/Shanghai-7) wheat genotypes under optimum (November 26) and late (December 11 and December 26) planting conditions. The dynamics of airborne conidia were studied using air samplers. The highest aerial concentrations of conidia and disease incidence of both pathogens on all four wheat genotypes were detected during the first 3?weeks of March under both optimum and late seeding conditions in both years. Compared to optimum sowing time (i.e. November 26), wheat genotypes had higher disease severity when planted late on December 11 and 26. The disease complex reduced grain yield by 20.5, 27.2 and 37.3?% for November 26, December 11 and December 26 plantings, respectively in 2004. The corresponding differences were 17.7, 23.6 and 30.2?% in 2005. The findings of this study provide valuable information on the epidemiology of spot blotch and tan spot, which could help in developing strategies for managing these diseases in South Asian region through the selection of suitable genotypes and planting dates.  相似文献   

13.
Fungicide resistance in plant pathogens is often caused by a single point mutation in a gene encoding fungicide target proteins. Such is the case for resistance to MBI-D (inhibitors of scytalone dehydratase in melanin biosynthesis) fungicides in rice blast fungus (Magnaporthe oryzae), which is caused by a mutation in the scytalone dehydratase gene that results in a replacement of valine with methionine at codon 75 of the fungicide target protein. PCR-Luminex, a novel system developed for high-throughput analysis of single nucleotide polymorphisms (SNPs) was successfully introduced to diagnose MBI-D resistance using specific oligonucleotide probes coupled with fluorescent beads. The PCR-Luminex system was further tested for its potential in identifying species causing Fusarium head blight on wheat. Four major pathogens, Fusarium graminearum (=F. asiaticum), F. culmorum, F. avenaceum, and Microdochium nivale, known to cause the disease, were tested, and the species were identified using the PCR-Luminex method. So far, this report is the first on the application of the DNA-based PCR-Luminex system in the area of crop protection and/or agricultural sciences.  相似文献   

14.
Reduced growth of plants and excessive generalised and spotty yellowing of leaves occurred in ornamental crotons that were infected with a geminivirus, which was detected by spot hybridization tests using a cloned probe derived from DNA-A of acalypha yellow mosaic geminivirus. The croton virus was transmitted by the whitefly,Bemisia tabaci, toNicotiana tabacum andAcalypha indica, in which it caused leaf curl and yellow mosaic, respectively, but it was not transmitted to five other species. Infected crotons may therefore serve as reservoirs of a geminivirus that is able to infect a crop species.  相似文献   

15.
Stagonospora nodorum blotch (SNB) caused by Stagonospora nodorum is a severe disease of wheat (Triticum aestivum) in many areas of the world. S. nodorum affects both seedling and adult plants causing necrosis of leaf and glume tissue, inhibiting photosynthetic capabilities, and reducing grain yield. The aims of this study were to evaluate disease response of 280 doubled haploid (DH) individuals derived from a cross between resistant (6HRWSN125) and susceptible (WAWHT2074) genotypes, compare quantitative trait loci (QTL) for seedling and adult plant resistance in two consecutive years, and assess the contribution of QTL on grain weight. Flag leaves and glumes of individuals from the DH population were inoculated with mixed isolates of S. nodorum at similar maturity time to provide accurate disease evaluation independent of morphological traits and identify true resistance for QTL analysis. Fungicide protected and inoculated plots were used to measure relative grain weight (RGW) as a yield-related trait under pathogen infection. The lack of similar QTL and little or no correlation in disease scores indicate different genes control seedling and adult plant disease and independent genes control flag leaf and glume resistance. This study consistently identified a QTL on chromosome 2DL for flag leaf resistance (QSnl.daw-2D) and 4BL for glume resistance (QSng.daw-4B) from the resistant parent, 6HRWSN125, explaining 4 to 19% of the phenotypic variation at each locus. A total of 5 QTL for RGW were consistently detected, where two were in the same marker interval for QSnl.daw-2D and QSng.daw-4B indicating the contribution of these QTL to yield related traits. Therefore, RGW measurement in QTL analysis could be used as a reliable indicator of grain yield affected by S. nodorum infection.  相似文献   

16.
The disease septoria tritici blotch of wheat is initiated by ascospores of the teleomorph Mycosphaerella graminicola or pycnidiospores of the anamorph Septoria tritici. We report for the first time the presence of the teleomorph, M. graminicola, in Denmark. With the objective of elucidating the importance of the teleomorph for the development of septoria tritici blotch, data on the occurrence of fruit bodies of the anamorph (pycnidia) and the teleomorph (pseudothecia) stages were collected over three growing seasons. Pseudothecia were present in the springs, however, high numbers of pseudothecia compared to pycnidia were not observed until July, too late to influence the epidemic. On an individual leaf layer, pycnidia were observed well before pseudothecia. As the leaves aged, progressively higher proportions of fruit bodies were observed to be pseudothecia. The period from the appearance of pycnidia to detection of pseudothecia was estimated as 29–53 days. At harvest, high proportions of sporulating fruit bodies in the crop were pseudothecia, suggesting that the primary source of inoculum for new emerging wheat crops in autumn is likely to be ascospores.  相似文献   

17.
Since the year 1991, up-to-date data about the actual infestation situations of the most important fungal diseases have been made available to the official advisory service and to the farmers by means of the “Monitoring for cereal diseases”. The classification of infestation is taken according to the scientifically elaborated thresholds of the Wheat Crop System Bayern and the Barley Crop System Bayern, respectively. The extensive data material allowed an evaluation over several years for the various cultivated areas. The least importance in winter wheat had eyespot, brown rust und yellow rust. Most exceedings of the thresholds were caused by Septoria tritici and Drechslera tritici-repentis. On about one third of the examined locations, exceedings of the threshold could already be noted before the growth stage “flag leaf just visible”. According to the infestation situation, in more than half of the cases one treatment would have been appropriate. In the past five years, the net blotch caused by Drechslera teres has turned out to be the most important disease in winter barley. With some difference in importance followed Rhynchosporium leaf blotch, powdery mildew and brown rust. At almost 80% of the locations, threshold exceedings were registered until the growth stage “flag life ligule just visible” (BBCH 39). In the majority of cases, the infestation situation makes a single treatment in winter barley appearing reasonable. In the years 2001–2004 the main pathogen in spring barley had been powdery mildew, followed by Drechslera teres and Rhynchosporium secalis. The exceedings of the thresholds had been spread over a broad range of growth stages. In the past five years the infestation of fungal diseases in triticale has been low. However since 2005 an increase of infestation, especially of powdery mildew, has been registered. The evaluation of the results from the “Monitoring for cereal diseases” over several years allows to estimate the risk of the different fungi in the regions. From that, conclusions about the fungicide intensities required in the average of cases can be drawn.  相似文献   

18.
Fungal leaf spot diseases of wheat (Triticum aestivum L.) in Nepal cause significant yield reduction. Although field testing has identified a few partially resistant cultivars, most wheat grown in Nepal lacks adequate resistance to leaf spot diseases. During 2009–2010, 116 local and commercial spring wheat cultivars and advanced breeding lines were selected from multi-year field experiments in Nepal and evaluated for seedling resistance to three leaf spot diseases: spot blotch, Stagonospora nodorum blotch (SNB) and tan spot races 1 and 5 (two of the most prevalent races) in the growth chambers at North Dakota State University, Fargo, ND, USA. The wheat cultivars and lines were artificially inoculated with individual pathogens or races at the two-leaf stage and disease reactions were evaluated 6 to 10 days after inoculation (DAI). Results indicated that 30%, 31%, 19% and 10% of the tested wheat cultivars and lines were resistant to spot blotch, SNB, tan spot races 1 and 5, respectively. Six advanced breeding lines (SW89-5422, BL 2127 = DANIAL88/HLB30//NL297, BL 3033, FILIN/IRENA/5/CNDO/R143//ENTE/MEXI-2/3/AE. SQUA (TAUS)/4WEAVER, GAN/AE.SQUARROSA (236)//DOY1/AE.SQUARROSA(447)/3/MAIZ/4/INQALAB91, Mayoor//TK SN1081/Ae. Squarrosa (222)/3/FCT, were resistant to spot blotch, SNB and tan spot race 1. Similarly, two wheat cultivars Chirya 3 and Chirya 7 were resistant to spot blotch, and tan spot races 1 and 5. The resistant wheat lines identified in this study represent potentially useful and untapped sources of resistance to multiple leaf spot diseases and should be utilized in wheat breeding programs in Nepal in order to develop wheat cultivars with broad-spectrum resistance.  相似文献   

19.
Seven four-way bread wheat mixtures were compared to their components (individual cultivars and two-way mixtures) for septoria tritici blotch severity, grain protein content, and grain yield. Four-way mixtures and two-way mixtures performed better than the average of individual pure line components. Disease severity and protein content were most influenced by mixtures, with mixture efficiencies being greater in the four-way than in the two-way mixtures. Performances of four-way mixtures in terms of diseased leaf area reduction, grain yield, 1000-grain weight, and grain protein content were better predicted by performances of two-way mixtures than by those of pure lines. Our results suggest that two-way mixtures should be screened to remove unfavourable cultivar pairs and those binary mixtures that show complementarity should be selected in order to construct four-way mixtures.  相似文献   

20.
Bacterial fruit blotch (BFB) of cucurbits, caused by Acidovorax avenae subsp. citrulli, is a serious threat to the watermelon and melon industries. To date, there are no commercial cultivars of cucurbit crops resistant to the disease. Here we assessed the level of tolerance to bacterial fruit blotch of various commercial cultivars as well as breeding and wild lines of melon, using seed-transmission assays and seedling-inoculation experiments. Selected cultivars were also tested in a greenhouse experiment with mature plants. All tested cultivars/lines were found to be susceptible to the pathogen, and most of them showed different responses (relative tolerance vs. susceptibility) in the different assays; however, some consistent trends were found: cv. ADIR339 was relatively tolerant in all tested assays, and cv. 6407 and wild lines BLB-B and EAD-B were relatively tolerant in seed-transmission assays. We also provide evidence supporting a strong correlation between the level of susceptibility of a cultivar/line and the ability of the pathogen to adhere to or penetrate the seed. To the best of our knowledge, this is the first attempt to assess melon cultivars/lines for bacterial fruit blotch response.  相似文献   

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