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1.
The oilseed rape cultivar Cresor was resistant to 14 isolates of Peronospora parasitica derived from crops of Brassica napus in the UK. Segregation for resistance to one isolate among F2 plants and F3 progeny of crosses between Cresor and the susceptible cultivars Victor and Jet Neuf indicated that resistance was controlled by a single gene. There was evidence that genetic background and environment could influence the phenotypic expression of this resistance. Two sexual progeny isolates derived from a homothallic isolate of P. parasitica avirulent on Cresor were completely virulent on this cultivar. This suggested that the parental isolate was heterozygous at a matching locus or loci for avirulence and demonstrated the race-specific nature of the resistance.  相似文献   

2.
The response of cotyledons of oilseed rape ( Brassica napus ssp. oleifera ) accessions to infection by isolates of Peronospora parasitica under controlled conditions was assessed on a 0–7 scale (disease reaction). In interactions scored 0–3, 4–5 and 6–7, the host was considered resistant, partially resistant and susceptible, respectively. Accession RES-26, selected from the spring oilseed rape cultivar Janetzkis, was partially resistant to isolate R1 and resistant to isolate P003 of P. parasitica , which distinguishes it from three previously described differential response groups ('A', 'B' and 'C') of accessions in B. napus . The resistance of RES-26 to isolate P003 seemed to be conditioned by a single, partially dominant gene and the resistance of RES-02, which belongs to group 'A' (resistant to R1 and P003), by two independent partially dominant genes. The gene for resistance to P003 in RES-26 is either closely linked, allelic or identical to one of the two genes for resistance in RES-02. Resistance of RES-02 to R1 is conditioned by a single, incompletely dominant gene. The genes for resistance to isolates R1 and P003 in RES-02 are either closely linked, allelic or identical. The cotyledonary leaves of each seedling responded independently when inoculated simultaneously each with a different isolate of the pathogen.  相似文献   

3.
Brassicaceae weeds are a widespread problem in Australian oilseed rape crops. The weeds not only compete for resources during crop growth, but also have the potential to reduce both oil and meal quality of the harvested crop. This study investigated oil and meal quality of weedy species from the Brassicaceae family that were collected throughout cropping regions of Australia. Eighty‐nine lines from 19 species were grown and evaluated in the same environment for their potential to contaminate Australian oilseed rape seed lots. Seed and flowering characteristics of each species were also examined. The glucosinolate concentration of most of the weedy species was greater than 100 μmol g?1 of oil‐free meal, well above the threshold for meeting oilseed rape quality. Erucic acid content of 18 of the 19 weedy species also exceeded the oilseed rape quality standard of less than 2% erucic acid. This study highlights the potential of the weedy species to reduce the quality of Australian oilseed rape crops.  相似文献   

4.
The hypothesis that enhancing the level of glucosinolates in leaves of oilseed rape would increase resistance to two fungal pathogens was tested. Thirty-three Brassica napus lines with variable leaf glucosinolate contents were assessed for susceptibility to infection by Leptosphaeria maculans and Alternaria spp. under field conditions. The data clearly showed that there was not a simple positive relation between glucosinolate content and resistance, and that the hypothesis can be refuted. The level of Alternaria infection of both leaves and pods was positively correlated with glucosinolate content, while for L. maculans there was no significant relationship between the two variables. It is suggested that these pathogens have become specialists on glucosinolate-containing taxa in an analogous way to insect herbivores.  相似文献   

5.
Verticillium wilt of oilseed rape ( Brassica napus ) is caused primarily by Verticillium longisporum and has become a serious problem in northern Europe. In order to evaluate whether V. longisporum and V. dahliae differ in their interaction with oilseed rape, phenotypical and molecular assessments were made. Oilseed rape plants for fungal assessments were inoculated with V. longisporum and V. dahliae via root-dipping and samples were taken from roots, stems, leaves, flowers, pods and seeds during plant development. The infection by V. longisporum was found to start mainly in lateral roots and root-hairs, followed by colonization of the xylem vessels and extensive spread in stems and leaves, whereas V. dahliae infected the main roots and remained in the region below the cotyledon node of the plants. Re-isolation studies, together with PCR analysis of samples taken from early growth stages through to fully ripe plants, showed that the onset of flowering was a critical phase for V . longisporum to colonize plants. No seeds infected with V. longisporum were found. Mycelial growth from V. dahliae but not V. longisporum was significantly reduced on media containing tissue from a low glucosinolate B. napus genotype compared with growth on media containing tissue from a high glucosinolate cultivar. The results of this study suggest that V. longisporum favours B. napus as host and that the transition from the vegetative to the generative phase is of importance for the spread of the fungus in oilseed rape plants.  相似文献   

6.
The growth of two isolates of the downy mildew fungus Peronospora parasitica , one obtained from cauliflower ( Brassica oleracea ) and the other from oilseed rape ( B. napus ) was assessed in their respective hosts of origin, and also in the alternative combination. Both isolates were capable of infecting either host, but there were marked contrasts in the time course and extent of mycelial development, the amounts of associated host-cell necrosis, and eventual intensity of sporulation. Oilseed rape, which was partially resistant to the isolate from cauliflower, exhibited extensive necrosis of mesophyll cells, in conjunction with reduced mycelial development, and delayed and reduced sporulation by the pathogen. The isolate from oilseed rape was virulent on both host species. Pathogenesis in the susceptible combinations was accompanied by large increases in electrolyte leakage, and increased activity of the enzymes β-glucosidase, ribonuclease, and peroxidase. Effects on chlorophyll content were variable and activities of acid phosphatase and acid phosphodiesterase were unaffected. Electrophoretic analyses of extracts from fungal sporangia and infected seedlings indicated that the large increases in β-glucosidase were of pathogen origin, while evidence from inhibitor studies suggested that enhanced ribonuclease activity was due to a new post-infectional form of the enzyme. The significance of these findings is discussed in relation to pathogenesis and host resistance mechanisms.  相似文献   

7.
Blackleg disease (phoma stem canker) of Brassica napus (canola, oilseed rape) is caused by the fungus Leptosphaeria maculans . In some regions of Australia, resistance in oilseed rape cultivars derived from B. rapa subs . sylvestris (e.g. cv. Surpass 400) became ineffective within three years of commercial release. The genetic control of avirulence in L. maculans towards cv. Surpass 400 is described. When Australian field isolates were screened on this cultivar, three phenotypic classes were observed; virulent, intermediate and avirulent. Analysis of crosses between fungal isolates varying in their ability to infect cv. Surpass 400 demonstrated the presence of two unlinked avirulence genes, AvrLm1 and AvrLmS . Complementation of isolates (genotype avrLm1 ) with a functional copy of AvrLm1 , and genotyping of field isolates using a molecular marker for AvrLm1 showed that virulence towards Rlm1 is necessary, but not sufficient, for expression of a virulent phenotype on cv. Surpass 400. Taken together, these data strongly suggest that cv. Surpass 400, with ' sylvestris -derived' resistance, contains at least two resistance genes, one of which is Rlm1 .  相似文献   

8.
ABSTRACT Verticillium wilt caused by the vascular fungal pathogen Verticillium longisporum is one of the most important pathogens of oilseed rape (Brassica napus sp. oleifera) in northern Europe. Because production of this major oilseed crop is expanding rapidly and no approved fungicides are available for V. longisporum, long-term control of the disease can only be achieved with cultivars carrying effective quantitative resistance. However, very little resistance to V. longisporum is available within the gene pool of oilseed rape, meaning that interspecific gene transfer from related species is the only possibility for broadening levels of resistance in current varieties. The amphidiploid species B. napus can be resynthesized by crossing the two progenitor species Brassica oleracea and Brassica rapa, hence resistant accessions of these two diploid species can be used as resistance donors. In this study a total of 43 potential B. rapa and B. oleracea resistance donors were tested with regard to their reaction to a mixture of two aggressive V. longisporum isolates, and resistances from diverse lines were combined by embryo rescue-assisted interspecific hybridization in resynthesized rapeseed lines. Progenies from crosses of the two B. rapa gene bank accessions 13444 and 56515 to the B. oleracea gene bank accessions BRA1008, CGN14044, 8207, BRA1398, and 7518 showed a broad spectrum of resistance in pathogenicity tests. Of 45 tested resynthesized lines, 41 lines exhibited a significantly higher level of resistance than the moderately V. longisporum-tolerant oilseed rape cultivar Express. These lines represent a promising basis for the combination of different resistance resources in new varieties.  相似文献   

9.
Jensen  Hockenhull  & Munk 《Plant pathology》1999,48(5):604-612
Seedlings of six cauliflower cultivars ( Brassica oleracea convar. botrytis var. botrytis ) were assessed for resistance to a Danish isolate of Peronospora parasitica , under controlled conditions. Resistance, characterized by restricted sporulation and necrotic dark flecks at the inoculation site on the cotyledons, was expressed in the hybrids 9306 F1, 9311 F1, and the open pollinated cultivar Perfection. Testing of the parent lines and F2 generations of the two resistant hybrids suggested that resistance was a dominantly inherited trait controlled by a single gene. Inoculation of the cultivars with seven isolates, from different geographical origins, showed that the resistance was isolate specific. The two hybrid cultivars expressing cotyledon resistance and two hybrids expressing susceptibility were assessed for adult plant resistance under field conditions. The AUDPC (Area Under the Disease Progress Curve), based on disease incidence and severity, revealed significant differences between the cultivars. At harvest, the cultivars exhibited significantly different levels of defoliation and curd attack. The cultivars 9306 F1 and 9311 F1 showed high levels of resistance in all assessments, whereas the two cultivars exhibiting susceptibility at the seedling stage, 9304 F1 and 9305 F1, also exhibited susceptibility through the adult plant stage. Thus, the resistance exhibited under field conditions resembled that identified at the seedling stage under controlled conditions. The results suggest that cotyledon resistance similar to that described could provide resistance throughout the adult plant stage, including curds.  相似文献   

10.
Phoma stem canker (blackleg), caused by Leptosphaeria maculans , is an important disease on oilseed rape (canola, rapeseed, Brassica napus , Brassica juncea , Brassica rapa ) causing seedling death, lodging or early senescence in Australia, Canada and Europe, but not in China. The two forms of L. maculans (A group and B group) that occur on oilseed rape are now considered to be separate species. The epidemiology and severity of phoma stem canker differs between continents due to differences in the pathogen population structure, oilseed rape species and cultivars grown, climate and agricultural practices. Epidemics are most severe in Australia, where only the A group occurs, and can be damaging in Canada and western Europe, where both A and B groups occur, although their proportions vary within regions and throughout the year. Epidemics are slight in China, where the A group has not been found. Dry climates (Australia, western Canada) lengthen the persistence of infected debris and may synchronize the release of airborne ascospores (after rain) with seedling emergence. L. maculans spreads from cotyledon and leaf infections down petioles to reach the stem, with infections on cotyledons and leaves early in the season producing the most damaging stem cankers at the stem base (crown). Development of both crown cankers and phoma stem lesions higher up stems is most rapid in regions with high temperatures from flowering to harvest, such as Australia and Canada. Breeding for resistance (genetic, disease escape or tolerance), stubble management, crop rotation and fungicide seed treatments are important strategies for control of phoma stem canker in all areas. Fungicide spray treatments are justified only in regions such as western Europe where high yields are obtained, and accurate forecasts of epidemic severity are needed to optimize their use.  相似文献   

11.
Low and high glucosinolate cultivars of oilseed rape were analysed for variation in both individual and total glucosinolate content up to 27 days after inoculation with turnip mosaic virus. Both infected and control plants of the two cultivars differed in the concentration of aliphatic, aromatic and indole glucosinolates. The biggest differences in glucosinolate content between the cultivars were found in the aliphatic and aromatic glucosinolate groups. Infected plants of the high glucosinolate cultivar, Solida, possessed lower amounts of glucosinolates, than did healthy control plants. Similar results were obtained with a low glucosinolate cultivar, S1. No significant difference was found between the two cultivars in resistance to turnip mosaic virus, using qualitative and quantitative ELISA to determine virus content in their tissues.  相似文献   

12.
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   

13.
Orobanche ramosa is a parasitic Angiosperm responsible for severe yield losses in several economical crops. It is a serious threat in oilseed rape in France and Morocco and is appearing in carrot crops in Morocco. In this study, several varieties of oilseed rape and carrot were screened in order to identify resistant cultivars and to characterize the resistance mechanisms involved. All the 15 oilseed rape varieties tested were susceptible. In carrot, the varieties 'Colmar à coeur rouge' and 'Nantaise demi-longue' were susceptible, whereas 'Palaiseau' and 'Buror' were resistant. In the susceptible 'Colmar à coeur rouge' carrot no defence reactions were found and the development of the parasite inhibited carrot tap root formation. In the resistant carrot varieties, the parasite germinated, became attached to the host root but became necrotic before emergence. In 'Buror' carrot, formation of a mechanical barrier was associated with the restriction to the cortex of the parasite. In maize cv. 'Vigni', a non-host of O. ramosa, thickening of xylem vessels, cell divisions in the central cylinder and formation of an encapsulation layer were observed in association with restricted development of Orobanche haustoria.  相似文献   

14.
大麦种质对叶斑病的抗性鉴定与评价   总被引：1，自引：0，他引：1  
 由麦根腐平脐蠕胞菌引起的叶斑病在世界各大麦种植区均有发生,严重影响大麦的产量和品质。选育和应用抗性品种是防控该病害最有效的策略,然而可利用的抗源非常有限。在本研究中对中国233份具有代表性的大麦种质资源进行成株期抗叶斑病田间人工接种鉴定,发现只有垦啤麦5号等10份材料对3个供试菌株都表现抗病,仅占供试材料的4.3%。另外对37份国内外重要的叶斑病抗源材料进行苗期及成株期抗叶斑病鉴定,结果显示成株期抗叶斑病材料所占比例为41%~46%,苗期抗性材料所占比例为50%~64%,其中ND17293等11份材料在苗期和成株期对3个菌株均表现为抗病,可作为抗源继续加以利用;基于上述鉴定结果,进一步分析发现供试大麦苗期对三个菌株的抗病比例均高于成株期抗病比例,说明大麦在不同生育期对叶斑病的抗性存在较大差异。另外发现大麦对B. sorokiniana不同致病类型的抗性也存在明显的专化性。  相似文献   

15.
Methods to assess light leaf spot ( Pyrenopeziza brassicae ) on winter oilseed rape cultivars were compared in laboratory, controlled-environment and field experiments. In controlled-environment experiments with seedling leaves inoculated at GS 1,4, the greatest differences in percentage area affected by P. brassicae sporulation were observed with inoculum concentrations of 4 × 103 or 4 × 104 spores mL−1, rather than 4 × 102 or 4 × 105 spores mL−1, but older leaves had begun to senesce before assessment, particularly where they were severely affected by P. brassicae . In winter oilseed rape field experiments, a severe light leaf spot epidemic developed in 2002/03 (inoculated, September/October rainfall 127·2 mm) but not in 2003/04 (uninoculated, September/October rainfall 40·7 mm). In-plot assessments discriminated between cultivars best in February/March in 2003 and June in 2004, but sometimes failed to detect plots with many infected plants (e.g. March/April 2004). Ranking of cultivar resistance differed between seedling experiments done under controlled-environment conditions and field experiments. The sensitivity of detection of P. brassicae DNA extracted from culture was greater using the PCR primer pair PbITSF/PbITSR than using primers Pb1/Pb2. P. brassicae was detected by PCR (PbITS primers) in leaves from controlled-environment experiments immediately and up to 14 days after inoculation, and in leaves sampled from field experiments 2 months before detection by visual assessment.  相似文献   

16.
为探明大白菜霜霉病病原菌寄生霜霉Peronospora parasitica对氟吡菌胺的敏感性,采用凹玻片保湿法和离体子叶浸泡法测定了氟吡菌胺对寄生霜霉不同生长发育阶段的抑制作用。结果表明:氟吡菌胺对寄生霜霉孢子囊萌发、芽管伸长、病斑扩展、孢囊梗形成及孢子囊产生均有不同程度的抑制作用,其中对孢子囊萌发和芽管伸长的抑制效果最显著,EC50值分别为0.113 3和0.291 8μg/m L;当氟吡菌胺质量浓度为8.00μg/m L时,对病斑扩展和产孢量的抑制率分别达到86.08%和72.48%,且对孢囊梗的产生也有显著的抑制作用。选用离体子叶浸泡法,测定了氟吡菌胺对从山东省不同地区采集分离的60株寄生霜霉菌株的毒力,发现菌株之间对药剂的敏感性差异较小,敏感性频率呈近似正态分布,其EC50值范围为0.163 2~0.802 2μg/m L,因此可以将其EC50平均值0.405 3μg/m L作为寄生霜霉对氟吡菌胺的敏感基线。  相似文献   

17.
Seedlings of 13 cultivars of oilseed rape ( Brassica napus ) were inoculated with 10 isolates of Leptosphaeria maculans. Three virulent isolates were identified which gave a resistant reaction on some cultivars normally considered susceptible. Further experiments to compare these with standard isolates confirmed the existence of a differential host-pathogen interaction. The breeding line 78/271, plus the cultivars Quinta, Garant, Norli and possibly Elvira differentiated the isolates tested while Jet Neuf, Rafal, Primor, Doral, Hercules, Rapora, Liraglu and Erra did not. The relevance of these findings to breeding for canker resistance in oilseed rape is discussed.  相似文献   

18.
Stem canker of crucifers is caused by an ascomycete species complex comprising of two main species, Leptosphaeria maculans and L. biglobosa. These are composed of at least seven distinct subclades based on biochemical data or on sequences of internal transcribed spacer (ITS), the mating type MAT1-2 or fragments of actin or beta-tubulin genes. In the course of a wide-scale characterization of the race structure of L. maculans from Western Australia, a few isolates from two locations failed to amplify specific sequences of L. maculans, i.e., the mating-type or minisatellite alleles. Based on both pathogenicity tests and ITS size, these isolates were classified as belonging to the L. biglobosa species. Parsimony and distance analyses performed on ITS, actin and beta-tubulin sequences revealed that these isolates formed a new L. biglobosa subclade, more related to the Canadian L. biglobosa 'canadensis' subclade than to the L. biglobosa 'australensis' isolates previously described in Australia (Victoria). They are termed here as L. biglobosa 'occiaustralensis'. These isolates were mainly recovered from resistant oilseed rape cultivars that included the Brassica rapa sp. sylvestris-derived resistance source, but not from the susceptible cv. Westar. The pathogenicity of L. biglobosa 'occiaustralensis' to cotyledons of most oilseed rape genotypes was higher than that of L. biglobosa 'canadensis' or L. biglobosa 'australensis' isolates.  相似文献   

19.
This paper describes the first large-scale Europe-wide survey of avirulence alleles and races of Leptosphaeria maculans. Isolates were collected from the spring rape cultivar Drakkar, with no known genes for resistance against L. maculans, at six experimental sites across the main oilseed rape growing regions of Europe, including the UK, Germany, Sweden and Poland. Additionally in Poland isolates were collected from cv. Darmor, which has resistance gene, Rlm9. In total, 603 isolates were collected during autumn in 2002 (287 isolates from Germany and the UK) and 2003 (316 isolates from Poland and Sweden). The identity of alleles at eight avirulence loci was determined for these isolates. No isolates had the virulence allele avrLm6 and three virulence alleles (avrLm2, avrLm3 and avrLm9) were present in all isolates. The isolates were polymorphic for AvrLm1, AvrLm4, AvrLm5 and AvrLm7 alleles, with virulence alleles at AvrLm1 and AvrLm4 loci and avirulence alleles at AvrLm7 and AvrLm5 loci predominant in populations. Virulent avrLm7 isolates were found at only one site in Sweden. Approximately 90% of all isolates belonged to one of two races (combinations of avirulence alleles), Av5-6-7 (77% of isolates) or Av6-7 (12%). Eight races were identified, with four races at frequencies less than 1%. The study suggested that Rlm6 and Rlm7 are still effective sources of resistance against L. maculans in oilseed rape in Europe. The results are comparable to those of a similar survey done in France in autumn 2000 and 2001.  相似文献   

20.
A range of 3, 5-disubstituted 1,3, 5-thiadiazinane-2-thiones are described which decompose in moist air to give organic isothiocyanates. Organic isothiocyanates are the main biologically active catabolites from the glucosinolate components of crucifers. The thiadiazinanethiones provide a source of organic isothiocyanates for biological studies and examples of tests with pathogens and insect pests of oilseed rape are given.  相似文献   

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