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1.
Summary Resistance to parasites can be distinguished into true resistance and pseudo or escape resistance. In the former resistance mechanisms operate after intimate contact between the host tissue and the parasite has been established. The resistance is expressed by a reduced growth of the parasite in or on the host tissue. Escape resistances operate before the parasite has made contact with the host tissue and is expressed by a reduced chance of such contacts. True resistance genes are assumed to act in a gene-for-gene way with virulence genes in the parasite. Genes governing escape resistances are supposed to function independently from genes in the parasite (no gene-for-gene action). It is deduced, that escape resistances and polygenic true resistances both are of a horizontal nature. Vertical resistance is to be found in the category of monogenic true resistances. 相似文献
2.
Durability of resistance against fungal, bacterial and viral pathogens; present situation 总被引：8，自引：0，他引：8
Jan E. Parlevliet 《Euphytica》2002,124(2):147-156
In evolutionary sense no resistance lasts forever. The durability of a resistance can be seen as a quantitative trait; resistances
may range from not durable at all (ephemeral, or transient) to highly durable. Ephemeral resistance occurs against fungi and
bacteria with a narrow host range, specialists. It is characterised by a hypersensitive reaction (HR), major gene inheritance and many resistance genes, which often occur
in multiple allelic series and/or complex loci. These resistance genes (alleles) interact in a gene-for-gene way with a virulence
genes (alleles) in the pathogen to give an incompatible reaction. The pathogen neutralises the effect of the resistance gene
by a loss mutation in the corresponding avirulence allele. The incompatible reaction is not elicited any more and the pathogenicity
is restored. The pathogens can afford the loss of many avirulences without loss of fitness. Durable resistance against specialised
fungi and bacteria is often quantitative and based upon the additive effects of some to several genes, the resulting resistance
being of another nature than the hypersensitive reaction. This quantitative resistance is present to nearly all pathogens
at low to fair levels in most commercial cultivars. Durable resistance of a monogenic nature occurs too and is usually of
a non-HR type. Resistance against fungi and bacteria with a wide host range, generalists, is usually quantitative and durable. Resistances against viruses are often fairly durable, even if these are based on monogenic,
race-specific, HR resistances. The level of specialisation does not seem to be associated with the durability of resistance.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
E. C. Roumen 《Euphytica》1992,64(1-2):143-148
Summary Six rice genotypes, differing in partial resistance, were exposed to three isolates of the blast pathogen. Of the variance due to host and pathogen genotypes, 39% was due to host genotype effects, 60% was due to isolate effects, and only 1% was due to host genotype × isolate interactions. Although small, this interaction variance was highly significant and mainly due to the IR50 × W6-1 and IR37704 × JMB8401-1 combinations. Although behaving largely as race-non-specific (large main effects only), the partial resistance cannot be classified as race-non-specific. The results suggest that minor genes for partial resistance operate in a gene for gene relationship with minor genes in the pathogen. 相似文献
4.
Nine populations of rye (Secale cereale L.; the cultivars ‘Kustro’, ‘Danko’ and ‘Carokurz’. a breeding population PA 14/75 and five Iranian primitive ryes) were tested with three or two pathotypes of powder)’ mildew (Erysiphe graminis DC. f. sp. secalis Marchal) to determine the frequencies of vertical resistances. Similarly, three populations of powder)’ mildew isolated from the above eultivars were tested with two rye pathodemes to estimate the frequencies of vertical virulences. Tests were carried out on leaf segments cultivated in vitro. To explain the pattern of the host-parasite interaction, a model with at least four resistance and virulence genes was required. In the rye populations the genotypes of most plants could be determined unambiguously whereas in the powdery mildew populations no unique classification of one-postule isolates was possible due to the limited number of rye differentials. Both the host and the pathogen populations were polymorphic for resistance and virulence, respectively. In all lye populations except PA 14/75 the resistance frequencies were low. In the mildew populations the virulence frequencies were high and complex races occurred rather frequently. The virulence frequencies were related to the resistance frequencies of the respective host population. Results were compared with mathematical host-parasite models accounting for gene-for-gene interaction and balancing natural selection. Observations agree well with theory. 相似文献
5.
Mohamed Labdi Rajinder S. Malhotra Ibrahim E. Benzohra Muhammad Imtiaz 《Plant Breeding》2013,132(2):197-199
Inheritance of resistance to race 4 of Ascochyta rabiei was studied in fifteen chickpea accessions known internationally for Ascochyta blight (AB) resistance. Resistance in ILC 200, ILC 5921, ILC 6043 and ILC 6090 was governed by a single recessive gene. Resistance in ILC 202 and ILC 2956 was conferred by two recessive complementary genes. In the case of ILC 5586, resistance was controlled by two dominant complementary genes and in the case of ILC 2506, two recessive genes with epistasis interaction were responsible for resistance. Resistance in ILC 3279, ILC 3856 and ILC 4421 was controlled either by three recessive genes or two recessives duplicated genes and in ILC 72, ILC 182 and ILC 187 resistance was polygenic in nature. The study provided insights into the genetics of Ascochyta blight resistance, and these could be used in crossing programmes to develop durable resistance. While the virulence spectrum of the pathogen in a region plays a crucial role in the deployment of resistance, ILC72, ILC182, ILC200, ILC442 and ILC6090 could provide acceptable level of resistance if incorporated into commercial cultivars. 相似文献
6.
番茄叶霉菌无毒基因的研究进展 总被引：1，自引：0，他引：1
无毒基因是病原物遗传因子,其编码的产物激发病原物与植物特异性相互作用。病原物无毒基因与植物抗病基因产物间直接或间接相互作用导致产生的基因对基因抗性是植物抗病性的重要形式。番茄与叶霉病之间的特异互作被认为是遵循Flor的“基因对基因”假说的典型体系。绝大多数已克隆的无毒基因之间,及其与已知蛋白之间,均无显著的序列同源性。无毒基因具有双重功能：在含瓦补抗性基因植物中表现无毒效应,而在不含互补抗性基因植物中显示毒性效应。本文综述了番茄叶霉菌无毒基因的多样性、意义、结构及其功能等等,了解病原菌无毒基因的结构及功能,有助于了解病原物与植物的识别机制,对认识植物的抗病性,特别是非寄主植物对病原菌的广谱抗病性也具有重要意义。 相似文献
7.
Richard N. Strange 《Euphytica》2006,147(1-2):49-65
Summary Grain legumes, in common with all other plants, are subject to biotic constraints of which pathogens form an important group.
They are variable in type, number, space and time and, most insidiously, in genetic constitution. Consequently, resistance
in the plant to a given pathogen may be quickly nullified by genetic alteration of the pathogen, particularly where this is
conferred by a single resistance gene. The products of such resistance genes usually recognise, directly or indirectly, a
component of the pathogen, which is encoded by a corresponding avirulence gene. Thus resistance and avirulence genes are specific
and complementary and the arrangement is referred to as a gene-for-gene relationship. It follows that alteration of the avirulence
gene of the pathogen to give a product that is no longer recognised by the product of the resistance gene of the plant gives
rise to a susceptible reaction. A possible solution to this problem is to pyramid several resistance genes, a procedure now
facilitated by the techniques of genetic modification. In other interactions genes that reduce susceptibility rather than
confer complete resistance have been found and in some cases the loci (quantitative trait loci) responsible have been mapped
to specific regions of particular chromosomes. The mechanisms by which these genes limit the virulence of the pathogen are
generally unknown. However, by gaining an understanding of the fundamental properties of a pathogen that are necessary for
pathogenicity or virulence it may be possible to counteract them. Candidates for such properties are toxins, enzymes and mechanisms
that interfere with constitutive or active defence of the plant. Reciprocally, understanding the properties of the plant that
confer susceptibility may allow selection of germplasm that lacks such properties. Among the candidates here are germination
stimulants of pathogen propagules and signals that promote the formation of infection structures. 相似文献
8.
Summary Seedlings of a differential barley (Hordeum vulgare L.) series (21 genotypes) and of six check genotypes were used in the greenhouse to assess variation in virulence among 20 single-spore isolates of the net blotch pathogen. Pyrenophora teres Drechs. f.teres Smedeg., collected from various sites in Finland. The experiment was run twice and symptom expression was recorded on the first three leaves. Analysis of second leaf symptom scores from Run 1 indicated differences in virulence between isolates, all of which were pathogenic, and differential resistance among the barleys. The virulence of P. teres isolates appeared to be conditioned by the host barley from which the isolate derived; the average virulence of isolates collected from a susceptible host was greater than that of isolates collected from a less susceptible host. Results from Run 2 were similar regarding resistance within the barleys, but variation in virulence among the P. teres isolates was not consistent with that from Run 1. CI 9819 caries duplicate genes for resistance to P. teres (Rpt1b and Rpt1c), and CI 7548 possesses Rpt3d. Both genotypes were highly resistant to all isolates. The Rpt1a gene of Tifang (CI4407) conferred resistance to all isolates in Run 2, but only to about half of the isolates in Run 1. The checks, including two of the symptomatically most resistant Nordic barley genotypes, were universally susceptible during these stringent tests. No selective pressure has been placed on Finnish isolates of P. teres through previous deployment of major resistance genes, and it is speculated that any variation in virulence among isolates is likely to be due to a combination of evolutionary forces including, natural selection, random genetic drift and gene flow. 相似文献
9.
Barley mildew in Europe: population biology and host resistance 总被引：5，自引：0，他引：5
M. S. Wolfe U. Brändle B. Koller E. Limpert J. M. McDermott K. Müller D. Schaffner 《Euphytica》1992,63(1-2):125-139
Summary Isolates of the barley mildew pathogen from the air spora over a large part of Europe and from fields of variety mixtures, were tested for virulence against 12 host resistance alleles. Subsamples were tested for their response to triadimenol fungicide and analyzed for 10 DNA loci using RAPD markers and PCR. There was a large range of haplotypes spread over Europe; irregularity in the distribution was probably due mainly to non-uniform use of the corresponding host resistances and fungicides. A large range of variation was also detectable within individual fields. Positive gametic disequilibria distorted the distribution of virulence alleles among haplotypes and reduced the number of haplotypes detectable in the sample. Analysis of the spread of the newly selectedVal3 allele into different European sub-populations indicated that gene flow throughout the population may be rapid for alleles that have a selective advantage.Fungicide resistance was widespread in areas known for intensive use of fungicides for mildew control. Four classes of fungicide response were detectable and particular virulence haplotypes were found to be characteristic for each class.Variety mixtures used in the former German Democratic Republic (GDR) reduced mildew infection, and thus fungicide use, during the years 1984–1991 despite the limited variation in host resistance among the mixtures. A tendency for complex pathogen races to increase in mixture crops was reversed by the large-scale re-introduction of fungicides for mildew control in 1991. The mixture strategy appeared to be more successful than using the same resistance alleles in pure monoculture or combining them in a single host genotype. 相似文献
10.
Genetic characterization of reniform nematode resistance for Gossypium arboreum accession PI 417895 
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下载免费PDF全文 Rotylenchulus reniformis is an important root pathogen of cotton in the south‐eastern United States, and management is hindered by the lack of host‐plant resistance in upland cotton (Gossypium hirsutum). The G. arboreum accession PI 417895 is highly resistant to R. reniformis, and a segregating population of 300 F2 plants was developed for phenotypic characterization of resistance. The population showed quantitative variation for nematode infection. Twenty plants showed no infection and were classified as escapes. Fifty‐four plants were classified as resistant or moderately resistant, whereas, 226 were classified as moderately susceptible or susceptible based on the nematode response of the susceptible parent, indicating resistance is a recessive trait, but these data did not support the single recessive gene model. Alternatively, this model would be supported if the 77 plants with a similar nematode response as observed for PI 417895 were classified as resistant. Twelve plants showed high levels of resistance and these data would support a two recessive gene model. Accession PI 417895 represents a new source of R. reniformis resistance with two major genes conferring resistance. Introgression of multiple resistance genes into G. hirsutum will require the development of larger populations to recover the resistant phenotype. 相似文献
11.
Quantitative resistance to downy mildew (Plasmopara halstedii) in sunflower (Helianthus annuus) 总被引：1，自引：1，他引：0
Downy mildew of sunflower, caused by the Oomycete, Plasmopara halstedii is at present controlled by major resistance genes. However, the pathogen has shown a considerable capacity for changes in
virulence and these resistance genes are overcome only a few years after they have been introduced into new sunflower varieties.
This paper presents research for quantitative, non-race-specific resistance independent of major genes. The reaction of cultivated
sunflower genotypes to field attack by downy mildew was studied over 4 years in several environments and in the presence of
the two most common races in France: 703 and 710. An experimental protocol with pre-emergence irrigation was developed, making
it possible to observe downy mildew reaction whatever the weather conditions. Significant levels of partial resistance were
observed in about 50 inbred sunflower lines among the 800 observed. These results suggest that it should be possible to select
for non-race-specific downy mildew resistance and to include it in modern varieties. However, since this non-specific resistance
is partial, it may be necessary to combine it with major gene resistance. Possible strategies are discussed to obtain durable
resistance to downy mildew. 相似文献
12.
Breeding for resistance to lentil Ascochyta blight 总被引：1，自引：0，他引：1
Ascochyta blight, caused by Ascochyta lentis, is one of the most globally important diseases of lentil. Breeding for host resistance has been suggested as an efficient means to control this disease. This paper summarizes existing studies of the characteristics and control of Ascochyta blight in lentil, genetics of resistance to Ascochyta blight and genetic variations among pathogen populations (isolates). Breeding methods for control of the disease are discussed. Six pathotypes of A. lentis have been reported. Many resistant cultivars/lines have been identified in both cultivated and wild lentil. Resistance to Ascochyta blight in lentil is mainly under the control of major genes, but minor genes also play a role. Current breeding programmes are based on crossing resistant and high‐yielding cultivars and multilocation testing. Gene pyramiding, exploring slow blighting and partial resistance, and using genes present in wild relatives will be the methods used in the future. Identification of more sources of resistance genes, good characterization of the host‐pathogen system, and identification of molecular markers tightly linked to resistance genes are suggested as the key areas for future study. 相似文献
13.
番茄细菌性斑点病是一种严重影响番茄质量和产量的世界性细菌性病害。目前对番茄与病原菌互作的研究取得了很大进展。番茄的Pto基因是指在基因对基因学说中,对引起番茄细菌性斑点病带有AvrPto基因的致病菌Pseudomonas syingae pv. tomato(PST)起抗性作用的基因。番茄中的抗病基因Pto与病原物中的无毒基因AvrPto互作是寄主对病原物互作的典型模式系统。这一模式识别的分子机制是Pto激酶与PST的两个效应子AvrPto和AvrPtoB中的任一个发生物理互作,然后与Prf一起激活下游多重信号传导途径,进而产生抗病性反应。已基本弄清Pto抗性传导途径,但对这个途径中的许多元件的作用及环节还有待于进一步研究。 相似文献
14.
R. S. S. Fraser 《Euphytica》1992,63(1-2):175-185
Summary Host resistance is the main means of control of plant virus diseases. This paper reviews the genetics of resistance and matching virulence. Theoretical models of basic compatibility between plant species and their viruses, and of resistance, are described and used to predict features of resistance genetics, and mechanisms. These predictions are compared with a survey of known examples of resistance.Resistance is mainly controlled at a single genetic locus, although more complex systems are known. About half of the resistance alleles studied were dominant, the remainder were either incompletely dominant or recessive. Doubt is cast on the reliability of assessing resistance genotypes (numbers of loci and dominace relationships) from distant phenotypic measurements such as symptom severity or plant growth. A model is proposed to reconcile apparent inconsistencies between genotype and phenotype.Dominant resistance alleles are strongly associated with virus localising mechanisms normally involving local lesions. Incompletely dominant and recessive alleles allow spread of the virus, but inhibit multiplication or symptom development. Fully recessive alleles may be associated with complete immunity.Most resistance genes in the survey had been overcome by virulent virus isolates with dominant localising resistance alleles especially vulnerable. Comparatively few resistance genes have proved exceptionally durable. Acquisition of virulence can be associated with loss of general pathogenic fitness, but in some cases this can be restored by further selection of the virus in resistant hosts.Virulence/avirulence determinants have been mapped to individual base changes in different functional regions of the viral genome. A virus may contain several virulence determinants and may develop a stable gene-for-gene relationship with a host having several resistance genes. It may be possible to design robust, oligogenic resistance systems which will be difficult for the virus to overcome. 相似文献
15.
Summary Foliar symptom severity of seedlings artificially inoculated with S. nodorum were used to idenify the type of gne action controlling resistance to this pathogen in the early generations of two wheat crosses. In both crosses a resistant spring wheat cultivar was crossed to a susceptible cultivar. Reciprocal crosses were included in the analysis to determine if the cytoplasm contributed in any significant degree to the level of resistance present.Results indicated that resistance was polygenic and that it could be explaned prinerpally by additive gene effects. Some differences in reciprocal crosses were evident, but a significant role for the eytoplasm in resistance is not indicated.Cooperative investigations of the Agricultural Research Service of the U. S. Department of Agriculture and the Montana Agricultural Experiment Station. Journal Paper No. 1210. 相似文献
16.
The population genetics of plant pathogens and breeding strategies for durable resistance 总被引：15，自引：0，他引：15
The durability of disease resistance is affected by the evolutionary potential of the pathogen population. Pathogens with
a high evolutionary potential are more likely to overcome genetic resistance than pathogens with a low evolutionary potential.
We will propose a set of guidelines to predict the evolutionary potential of pathogen populations based on analysis of their
genetic structure. Under our model of pathogen evolution, the two most important parameters to consider are reproduction/mating
system and gene/genotype flow. Pathogens that pose the greatest risk of breaking down resistance genes are those that possess
a mixed reproduction system, with at least one sexual cycle per growing season and asexual reproduction during the epidemic
phase, and a high potential for gene flow. The lowest risk pathogens are those with strict asexual reproduction and low potential
for gene flow. We will present examples of high- and low-risk pathogens. Knowledge of the population genetic structure of
the pathogen may offer insight into the best breeding strategy for durable resistance. We will present broad guidelines suggesting
a rational method for breeding durable resistance according to the population genetics of the pathogen.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
17.
Important microevolutional processes have taken place in the wheatpowdery mildew population over the last thirty years. There has been aconsiderable change in the race composition of the pathogen populationand in the prevalent races. Of the 78 races identified, only eleven have`lived' for more than 15 years. Many races were only isolated in one ortwo years. The number of virulence genes rose from 2.03 in 1973 to 5.63in 1993. On the basis of race composition and virulence the wheatpowdery mildew population between 1971 and 1999 can be divided intofour distinct groups. A large proportion of the powdery mildew isolates arevirulent to most resistance genes. Complete resistance is provided byresistance genes Pm4a (Khapli) and partial resistance by Pm2 + Mld (Halle st. 13471), Pm4b+ (TP 315/2) and Pm1 + 2 + 9 (Normandie). The majority of cultivated varieties carry theresistance gene Pm8 due to the presence of the 1B/1R translocation. 相似文献
18.
Pham X. Tung 《Euphytica》1992,61(1):73-80
Summary Genetic variance components and heritability were estimated for resistance to bacterial wilt in a population of tetraploid potato with resistance derived from several specific sources. Both additive and non-additive variance components were significant. Their relative magnitudes indicated the importance of non-additive gene action in the genetic control of the resistance. Narrow-sense heritability was relatively low for both disease index and % survival indicating that progress in population development would be slow. Broad-sense heritability was, however, relatively high which promises success of clonal selection in developing clonal resistant cultivars. 相似文献
19.
Inheritance of stalk rot resistance in cauliflower (Brassica oleracea var. Botrytis L.) 总被引：2，自引：0，他引：2
Summary The inheritance of resistance in cauliflower to stalk rot (Sclerotinia sclerotiorum (Lib.) de Bary) was investigated in population from six generations of six crosses. Disease incidence was recorded on 4 parents, 6 Fs
1, 6 Fs
2 and 12 back-crosses in a screenhouse under artificially created epiphytotic conditions. Resistance to stalk rot in this set of parents was found to be polygenic and under the control of recessive genes and due primarily to additive gene action. A breeding strategy emphasizing recurrent selection should lead to improvement in resistance. 相似文献
20.
L. H. M. Broers 《Euphytica》1989,44(3):273-282
Summary Partial resistance (PR) in wheat to wheat leaf rust (Puccinia recondita f.sp. tritici) is characterized by a slow epidemic build-up despite a susceptible infection type. Two greenhouse tests and two field tests, in which 11 spring wheat cultivars were exposed to five wheat leaf rust races, revealed some indication for race-specificity of PR.In the greenhouse, the expression of PR was highly dependent on the environment. Significant cultivar-race interactions in the first experiment were lost in the second experiment probably due to cultivar-environment and cultivar-race-environment interactions.In the polycyclic field tests several factors played a role in explaining the inconsistency of the cultivar-race interactions, such as differences in initial inoculum, genotypic differences in earliness, interplot interference or environmental conditions.One cultivar-race combination showed a significant but small interaction towards susceptibility in both field experiments. The interaction was probably too small to detect in the monocyclic greenhouse tests. The results do not conflict with the idea that a gene-for-gene relationship could exist between PR-genes in the host and genes in the pathogen.Some problems with regard to the selection of PR in wheat to wheat leaf rust are discussed. 相似文献