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1.
Hilal Ozkilinc Omer Frenkel Dani Shtienberg Shahal Abbo Amir Sherman Abdullah Kahraman Canan Can 《European journal of plant pathology / European Foundation for Plant Pathology》2011,131(3):529-537
Ascochyta blight, caused by Didymella rabiei, affects both domesticated chickpea and its congeneric wild relatives. The aim of this study was to compare the aggressiveness
of D. rabiei isolates from wild and domesticated Cicer spp. in Turkey and Israel on wild and domesticated hosts from both countries. A total of eight isolates of D. rabiei sampled from C. pinnatifidum, C. judaicum and C. arietinum in Turkey and Israel was tested on two domesticated chickpea cultivars and two wild Cicer accessions from Turkey and Israel. Using cross-inoculation experiments, we compared pathogen aggressiveness across the different
pathogen and host origin combinations. Two measures of aggressiveness were used, incubation period and relative area under
the disease progress curve. The eight tested isolates infected all of the host plants, but were more aggressive on their original
hosts with one exception; Turkish domesticated isolates were less aggressive on their domesticated host in comparison to the
aggressiveness of Israeli domesticated isolates on Turkish domesticated chickpea. C. judaicum plants were highly resistant against all of the isolates from different origins except for their own isolates. Regardless
of the country of origin, the wild isolates were highly aggressive on domesticated chickpea while the domesticated isolates
were less aggressive on the wild hosts compared with the wild isolates. These results suggest that the aggressiveness pattern
of D. rabiei on different hosts could have been shaped by adaptation to the distinct ecological niches of wild vs. domesticated chickpea. 相似文献
2.
A genetic map was developed for the ascomyceteDidymella rabiei (Kovachevski) v. Arx (anamorph:Ascochyta rabiei Pass. Labr.), the causal agent of Ascochyta blight in chickpea (Cicer arietinum L.). The map was generated with 77 F1 progeny derived from crossing an isolate from the U.S.A. and an isolate from Syria. A total of 232 DAF (DNA Amplification
Fingerprinting) primers and 37 STMS (Sequence-Tagged Microsatellite Site) primer pairs were tested for polymorphism between
the parental isolates; 50 markers were mapped, 36 DAFs and 14 STMSs. These markers cover 261.4cM in ten linkage groups. Nineteen
markers remained unlinked. Significant deviation from the expected 1:1 segregation ratios was observed for only two markers
(Prob. of χ2<0.05). The implications of our results on ploidy level of the asexual spores are discussed.
http://www.phytoparasitica.org posting Sept. 5, 2002. 相似文献
3.
The distribution of mating types and diversity in virulence of Didymella rabiei populations were studied in Israel from 1997 to 1999. Forty-one monoconidial D. rabiei isolates from 18 commercial fields distributed among all the chickpea production areas of the country were paired with MAT1-1 and MAT1-2 mating type tester isolates of D. rabiei. Both mating types were found in all chickpea production areas of the country. Of the 18 fields sampled, MAT1-1 was observed in 44%, and MAT1-2 in 88% of the sites. In some sites both mating types were present in close proximity, suggesting that sexual reproduction
of the pathogen was feasible. The contribution of sexual reproduction of the fungus to virulence diversity was tested on detached
leaves of six differential chickpea cultivars. Nine isolates were derived from different well separated foci (derived from
ascospores as inoculum) and eight isolates were derived from a single, well defined infection focus (derived from sister conidia).
In the analyses of variance the cultivar × isolate interaction showed no significant (P of F>0.09) effect on disease incidence; the chickpea cultivars differed significantly (P of F<0.0001) in their response to D. rabiei; and the isolate effect was highly significant (P of F = 0.0007) for the conidial population, but not significant (P of F>0.1) among isolates of the ascosporic population. Nevertheless, when comparing a cultivar at a time, the ascosporic and conidial
populations did not differ significantly (P of F>0.1) in their virulence diversity. Virulence of 41 isolates collected from the different chickpea fields was tested on detached
leaves of four Israeli cultivars that differ in their field response to D. rabiei. The cultivar × isolate interaction showed no significant effect (P of F = 0.95) on disease incidence. The main effects of cultivar and isolate on disease incidence were highly significant (P of F<0.0001). Accordingly, our data do not support the hypothesis that there is pathogenic specialization in the D. rabiei–C. arietinum pathosystem in Israel. 相似文献
4.
H. Ozkilinc O. Frenkel S. Abbo R. Eshed A. Sherman D. Shtienberg R. Ophir C. Can 《Plant pathology》2010,59(3):492-503
The Fertile Crescent is the centre of domestication of chickpea (Cicer arietinum) and also the place of origin of its pathogens. Agrosystems provide different environments to natural eco‐systems, thus imposing different types of selection on pathogens. Here, the genetic structure and in vitro temperature growth response of the chickpea pathogen Didymella rabiei from domesticated chickpea (59 isolates from Turkey and 31 from Israel) and wild Cicer spp. (three isolates from Turkish C. pinnatifidum and 35 from Israeli C. judaicum) were studied. Six sequence‐tagged microsatellite site (STMS) primer pairs were used to determine the genetic structure of the 128 D. rabiei isolates. Turkish isolates exhibited the highest genetic diversity (H = 0·69). Turkish and Israeli D. rabiei from domesticated chickpea were genetically closer to each other than isolates from the wild Cicer spp. Analysis of molecular variance showed that 54% of the genetic variation resided between isolates from wild and domesticated origins. EF1‐α sequences distinguished between D. rabiei isolates from domesticated and wild Cicer spp. by four polymorphic sites. Nevertheless, a certain degree of mixing between isolates from wild and domesticated origin was demonstrated using the Bayesian algorithm as well as with principal coordinates analysis. Isolates sampled from domesticated chickpea from both countries were better adapted to temperatures typical of Levantine spring and had a significantly larger colony area at 25°C than at 15°C (typical Levantine winter temperature). These observations were in accordance to the heritability values of the temperature growth response. 相似文献
5.
ABSTRACT A rice isolate of Magnaporthe grisea collected from China was avirulent on rice cvs. Hattan 3 and 13 other Japanese rice cultivars. The rice cv. Hattan 3 is susceptible to almost all Japanese blast fungus isolates from rice. The genetic basis of avirulence in the Chinese isolate on Japanese rice cultivars was studied using a cross between the Chinese isolate and a laboratory isolate. The segregation of avirulence or virulence was studied in 185 progeny from the cross, and monogenic control was demonstrated for avirulence to the 14 rice cultivars. The resistance gene that corresponds to the avirulence gene (Avr-Hattan 3) is thought to be located at the Pik locus. Resistance and susceptibility in response to the Chinese isolate in F(3) lines of a cross of resistant and susceptible rice cultivars were very similar to the Pik tester isolate, Ken54-20. Random amplified polymorphic DNA markers and restriction fragment length polymorphism markers from genetic maps of the fungus were used to construct a partial genetic map of Avr-Hattan 3. We obtained several flanking markers and one co-segregated marker of Avr-Hattan 3 in the 144 mapping population. 相似文献
6.
Antonio Trapero-Casas Francisca Luque-Márquez Walter J. Kaiser 《European journal of plant pathology / European Foundation for Plant Pathology》2012,134(4):773-782
Ascochyta blight caused by Didymella rabiei (anamorph: Ascochyta rabiei) is an important foliar disease of chickpea in many countries. The fungus is heterothallic and requires the pairing of two compatible mating types for the teleomorph to develop. In nature, the teleomorph only develops on chickpea debris that overwinters on the soil surface in the presence of both mating types. When natural and synthetic agar media were seeded with conidial suspensions of compatible isolates of D. rabiei from Spain and the United States and incubated under favourable conditions for teleomorph development, the teleomorph only developed on 2?% water agar amended with powdered chickpea stems or hot water extracts of chickpea stems, but not on 14 other natural or synthetic media. Ascospore isolates of D. rabiei from pseudothecia that developed on agar media were indistinguishable in cultural and morphological characteristics from isolates of the fungus from chickpea. Production of pseudothecia and ascospores on the best culture medium was always lower than on stem pieces of chickpea straw used as a control treatment. Ascospores discharged from pseudothecia that developed on powdered chickpea stem media onto chickpea seedlings were pathogenic, inducing symptoms identical to those caused by ascospores from chickpea stem pieces or conidia from a chickpea isolate of the fungus. This is the first report of the teleomorph of D. rabiei developing on culture media. 相似文献
7.
Chao-Xi LUO Hiromi HANAMURA Hiroyo SEZAKI Motoaki KUSABA Hiroshi YAEGASHI 《Journal of General Plant Pathology》2002,68(4):300-306
A genetic cross between rice-field isolates of Magnaporthe grisea produced progeny segregating for avirulence/ virulence on six rice cultivars among nine race differentials, while on three
other cultivars, Shin 2 (Pik-s), Aichi Asahi (Pia) and Ishikari Shiroke (Pii), parental and progeny isolates were all virulent. Based on segregation ratios in 115 progeny isolates, avirulence on Kanto
51 (Pik), Yashiro-mochi (Pita), Fukunishiki (Piz) and Toride 1 (Piz-t) is under monogenic control. On Tsuyuake (Pik-m) and Pi No. 4 (Pita-2), however, a disproportionate ratio in the segregation was observed, suggesting that avirulence on these two cultivars is
controlled by two or more genes. Assuming that the avirulence gene AvrPik-m consists of at least two genes, AvrPik-m1 and AvrPik-m2, each of which functions in the whole gene AvrPik-m, and that one of AvrPik-m1 and AvrPik-m2 is AvrPik, we could account for the disproportion in the avirulence/virulence segregation of the progeny. This hypothesis would also
be consistently applied for avirulence gene AvrPita-2. There seem to be two types of the avirulence genes : AvrPik-m, that is comprised of the tightly linked genes, AvrPik-ml (=AvrPik) and AvrPik-m2, and AvrPita-2, that is comprised of the loosely linked genes AvrPita-2A (=AvrPita) and AvrPita-2B. As one possible explanation of the rice resistant reaction to blast, multiple specificity was suggested for the first time
for the blast fungus. On the contrary, the avirulence genes AvrPiz and AvrPiz-t were inherited independently, despite the corresponding genes for resistance (Piz and Piz-t) being located at the same locus. The cross of rice blast isolates (races 447 and 337) produced only 25 kinds of races in
the progeny, although theoretically about 64 kinds of races should be produced if six avirulence genes segregated independently.
Because no progeny are with AvrPik (or AvrPita) and without AvrPik-m (or AvrPita-2), the number of races theoretically should be 36 at most. A number of strains, such as races 377 and 737, with a single avirulence
gene were obtained from this cross. These strains may be valuable for analysis of resistance genes in rice plant.
Received 19 August 2002/ Accepted in revised form 11 November 2002 相似文献
8.
Leah L. Granke Lina M. Quesada-Ocampo Mary K. Hausbeck 《European journal of plant pathology / European Foundation for Plant Pathology》2012,132(2):281-296
Phytophthora capsici causes root, crown, and fruit rot of vegetable and tropical hosts. Cucumber, zucchini, tomato, and pepper fruits were inoculated
using 6-mm-diameter agar plugs of P. capsici, incubated in clear plastic boxes at room temperature (25 ± 2°C and 100% relative humidity), and virulence was estimated
by measuring the lesion diameter, pathogen growth diameter, and pathogen sporulation density three (cucumber, zucchini) or
four (tomato, pepper) days later. When isolates were grouped by genetic cluster, significant differences in virulence were
observed on cucumber and zucchini, with isolates belonging to genetic cluster five causing larger lesions than isolates from
genetic cluster six. On tomato, no significant differences were observed for isolates grouped by genetic cluster, but isolates
from vegetable crops were generally more virulent than isolates from tropical hosts. Isolates from fabaceous hosts sporulated
better on cucumber fruits than isolates from solanaceous hosts. Isolates from vegetable hosts sporulated better on zucchini
than isolates from tropical hosts. No significant differences in lesion diameter were noted on pepper when isolates were grouped
by host family of origin or genetic cluster, but differences in pathogen sporulation were apparent by host family. Our findings
suggest that isolate characteristics such as host family of origin and genetic cluster membership may be used to guide initial
isolate selection for cucurbit fruit resistance screening. Final isolate selection should incorporate the phenotypic and genetic
diversity of P. capsici, including isolates with differing virulence to the host organ of interest. 相似文献
9.
J. A. Navas-Cortés E. Pérez-Artés R. M. Jiménez-Diaz A. Llobell B. W. Bainbridge J. B. Heale 《Phytoparasitica》1998,26(3):199-212
Eleven pathotype groups (A-K), including five not previously reported, ofDidymella rabiei (anamorphAscochyta rabiei), representing isolates of the pathogen from Ascochyta blight-affected chickpeas mainly from India, Pakistan, Spain and the
USA, were characterized using 44 single-spore isolates tested against seven differential chickpea lines. Of 48 isolates tested
for mating type, 58% belonged to MAT 1-1 and 42% to MAT 1-2. Thirty-nineD. rabiei isolates, as well as two isolates ofAscochyta pisi and six isolates of unrelated fungi, were analyzed using Randomly Amplified Polymorphic DNAs (RAPDs) employing five primers
(P2 at 40°C, and OPA3, OPC1, OPC11 and OPC20 at 35°C). Computer cluster analysis (UPGMA / NTSYS-PC) detected a relatively
low level of polymorphism among all theD. rabiei isolates, although atca 7% dissimilarity,ca 10 RAPD groups [I-X] were demarcated, as well as subclustering within the larger groups. By the same criteria, the maximum
dissimilarity for the whole population ofD. rabiei isolates wasca 13%. No correlation was found between different RAPD groups, pathotype, or mating type ofD. rabiei, although some evidence of clustering based on geographic origin was detected. The use of RAPDs enabled us to identify specific
DNA fragments that may have a potential use as genetic markers in sexual crosses, but none which could be used as virulence
markers. 相似文献
10.
F. F. Jamil N. Sarwar M. Sarwar J. A. Khan J. Geistlinger G. Kahl 《Physiological and Molecular Plant Pathology》2000,57(6):243
Pathogenic and genetic diversity in Ascochyta rabiei populations in Pakistan were evaluated. Biological pathotyping of 130 A. rabiei isolates (obtained from hierarchically collected samples) was conducted on a set of three chickpea differentials, i.e. ILC 1929 (susceptible), ILC 482 (tolerant) and ILC 3279 (resistant), under controlled conditions. Disease severity data were recorded 12 days after inoculation. Statistical analysis grouped the isolates into three pathotype classes. Four isolates belonged to pathotype I (least aggressive), 79 isolates to pathotype II (medium aggressive) and 47 isolates to pathotype-III (highly aggressive).Genetic analysis was performed using RAPDs and oligonucleotide fingerprinting, where Hinf I-digested DNA was hybridized to the32P-endlabeled oligonucleotide probes (CAA)5, (GAA)5, (GA)8, (CA)8and (GATA)4. Dendrograms produced by cluster analysis discriminated 46 genotypes in the A. rabiei population of Pakistan. Genetic distances and relatedness between isolates were calculated. At a genetic distance of 0.3, genotypes were divided into six distinct genotype groups A, B, C, D, E and F containing 16, 11, 2, 5, 5 and 7 isolates, respectively. Most of the genotypes were area specific or predominated in certain areas but did not belong to a distinct pathotype, while most of the aggressive isolates (pathotype III) occurred in Northern Punjab and in the North Western Frontier Province. 相似文献
11.
Rajaâ Jebbouj Brahim El Yousfi 《European journal of plant pathology / European Foundation for Plant Pathology》2010,127(4):521-544
Knowledge of pathotype diversity and virulence in local populations of Pyrenophora teres is a prerequisite to screening for durable resistance to net blotch. The current study aimed to quantify the virulence level
of Moroccan isolates, identify and designate existing pathotypes, and select resistant genotypes. We developed a method for
virulence quantification of P. teres isolates based on a conversion of infection responses into frequencies for use in correspondence analysis. Coordinates of
the first axis of this analysis had a virulence spectrum and ranked isolates from virulent to avirulent. Mixed model analysis
was also devised for virulence quantification. Coordinates of the first dimension of correspondence analysis were linearly
correlated to BLUPs (Best Linear Unbiased Predictors) of the mixed model. A genotype by genotype by environment model (GGE)
coupled with cluster analysis differentiated P. teres isolates into ten and nine pathotypes for net- and spot-forms respectively. Populations of these two forms were dissimilar
in terms of classes of virulence. For P. teres f. maculata, avirulent, moderately virulent and highly virulent isolates represented one-third of the population, whereas 90% of P. teres f. teres population was composed of avirulent to moderately avirulent isolates. Barley differential sets were subsequently reduced
to two new sets that simplified pathotyping through a key code based on resistant or susceptible reactions. Dendrograms of
cluster analysis based on GGE analysis depicted the stability of a genotype’s reactions across all isolates, and using only
resistant cultivars as sources of resistance to control net blotch disease would, based on this analysis, fail to control
all pathotypes. Therefore, we propose an alternative breeding strategy to control net blotch effectively. 相似文献
12.
ABSTRACT Spot blotch, caused by Cochliobolus sativus, is one of the most common foliar diseases of barley in the upper midwest region of the United States. To examine the genetics of host-specific virulence in C. sativus, a cross was made between isolate ND90Pr (which exhibits high virulence on barley genotype Bowman and low virulence on genotype ND 5883) and ND93-1 (which exhibits low virulence on both genotypes). Ascospore progeny segregated 48:55 for low virulence/high virulence on Bowman, indicating the presence of a single virulence gene in isolate ND90Pr. To complement the study of host-specific virulence in the pathogen, an experiment also was conducted on the genetics of specific resistance in the host. Progeny from a Bowman/ND 5883 cross were evaluated for their infection responses (IRs) to isolate ND90Pr at the seedling stage. The F(2) population segregated 1:3 for low IRs (resistant)/high IRs (susceptible), indicating the presence of a single resistance gene in genotype ND 5883. This result was confirmed in the F(3) generation, as a 1:2:1 ratio was found for homozygous resistant, segregating, and homozygous susceptible families, respectively. The data from this study demonstrate that both virulence in the pathogen and resistance in the host are under monogenic control in this specific host genotype/fungal isolate combination. 相似文献
13.
Antonio Trapero-Casas Walter J. Kaiser 《European journal of plant pathology / European Foundation for Plant Pathology》2009,125(4):573-587
Various crop and weed species were infected naturally by Didymella rabiei (anamorph: Ascochyta rabiei) in blight-affected chickpea fields in the Palouse region of eastern Washington and northern Idaho, USA. The fungus was isolated
from asymptomatic plants of 16 species commonly found in commercial crops in this region. Isolates of the pathogen from crop
and weed species were pathogenic to chickpea and indistinguishable in cultural and morphological characteristics from isolates
of D. rabiei from chickpea. Both mating types of D. rabiei were isolated from eight naturally infected plant species. Chickpeas were infected by D. rabiei when plants emerged through infested debris of seven crop and weed species. The teleomorph developed on overwintered tissues
of seven plant species infected naturally by D. rabiei in a blight screening nursery and on debris of wheat, white sweet clover and pea inoculated with ascospores of D. rabiei or conidia of two compatible isolates of the pathogen. Didymella rabiei naturally infected 31 accessions of 12 Cicer spp. and the teleomorph developed on the overwintered debris of all accessions, including those of three highly resistant
perennial species. The fungus developed on the stem and leaf pieces of ten plant species common to southern Spain inoculated
with conidia of two compatible isolates of D. rabiei, and formed pseudothecia with asci and viable ascospores on six of ten species and pycnidia with conidia on all plant species. 相似文献
14.
María Laura Toulet Diego A. Neira Marcela Escobar E. Mariano Pardo Marta E. Arias Leonardo Daniel Ploper Björn Welin Atilio Pedro Castagnaro Nadia Regina Chalfoun 《Plant pathology》2022,71(4):843-859
Soybean target spot, caused by the fungus Corynespora cassiicola, is an important disease in northwestern Argentina (NWA). A cultural, morphological, and virulence characterization of 24 C. cassiicola isolates from different geographic localities in NWA was performed. The isolates were classified into five different cultural phenotypes, one of which has not been previously described. The ribosomal DNA internal transcribed spacer region sequence from five representative isolates (587 bp) exhibited 100% identity with C. cassiicola. A high variability of conidial morphology was observed among isolates, but no correlation with cultural phenotype was observed. When the soybean cultivar A 8000 RG was challenged with the 24 isolates, different degrees of virulence were observed, ranging from highly virulent to nonvirulent. No association of virulence with cultural or morphological characters was observed, but a relationship with geographical origin was demonstrated. Histopathological studies were performed on a nonvirulent and a highly virulent isolate. Microscopic observations of infected tissues of the former showed low mycelium development restricted to the upper epidermis, a thickening of the cuticle and primary wall of subepidermal cells, and accumulation of callose in phloematic vessels. In tissue infected with the latter, there was abundant mycelium development accompanied by cellular disorganization in mesophyll cells. Pathological challenges of isolates on nine different cultivars indicated that the degree of virulence of isolates depends on the plant genotype, demonstrating that the C. cassiicola–soybean interaction is highly specific. Understanding the genetic basis of this interaction will provide new information for better disease management and breeding strategies. 相似文献
15.
Thomas Thomidis 《Phytoparasitica》2002,30(2):191-193
The virulence ofPhytophthora citrophthora isolated from various host-plants on three peach rootstocks (GF677, PR204, KID I) was examined. There was no significant
difference among the rootstocks with respect to their susceptibility to testedP. citrophthora isolates. The most virulent isolate originated from sycamore (Acer pseudoplatanus); isolates from pistachio trees (Pistacia vera) also showed high virulence but were significantly less virulent than the sycamore isolate. Isolates originating from plum
(Prunus domestica), almond (Prunus amygdalus) and lemon (Citrus limon) trees were moderately virulent on peach rootstocks; those from cyclamen (Cyclamen persicum) showed the lowest virulence of those tested. There was thus great variation in virulence among the testedP. citrophthora isolates. It is possible that the isolates ofP. citrophthora from sycamore, pistachio, plum, almond and lemon trees are a threat to peach trees, whereas the low virulence of the isolates
from cyclamen hosts suggests that these pathogens are not a serious threat to peach trees.
http://www.phytoparasitica.org posting Jan. 3, 2002. 相似文献
16.
Mamta Sharma Suresh Pande Abhishek Rathore 《European journal of plant pathology / European Foundation for Plant Pathology》2010,128(3):325-331
Ascochyta blight (AB, Ascochyta rabiei (Pass.) Lab.) is one of the most important foliar disease of chickpea (Cicer arietinum L.), globally. Chickpea is attacked by AB at any growth stage in cool and humid weather depending on the inoculum availability.
However, the disease epidemics are most prominent during the flowering and podding growth stages. The main objective of this
study was to determine the effect of growth stages of chickpea on the genetic resistance of AB and use this information in
a resistance breeding program. Two susceptible and two moderately resistant chickpea cultivars were spray inoculated at seedling
(GS1), post-seedling (GS2), vegetative (GS3), flowering (GS4) and podding (GS5) growth stages with A. rabiei conidial suspension under controlled environment conditions. Irrespective of crop cultivars the incubation period (IP) was
shorter in GS1, GS4 and GS5 and was significantly extended in GS2 and GS3. Symptom development was delayed significantly in
moderately resistant cultivars. The AB severity 10 days after inoculation ranged between 7 and 9 on susceptible cultivars
and 3 and 5 on moderately resistant cultivars. Further the correlation coefficient of disease severity between GS1, GS4 and
GS5 was highly significant (r = 0.95) indicating that, evaluation for resistance to AB can be done at GS 1 (seedling stage), and or GS4 (flowering stage)
to GS5 (podding stage) growth stages of chickpea. This supports the evaluation for AB resistance using 10-day-old-seedlings
in controlled environment at ICRISAT and adult plant field screening at hot-spot locations in Dhaulakuan and Ludhiana in India. 相似文献
17.
Tobin L. Peever 《European journal of plant pathology / European Foundation for Plant Pathology》2007,119(1):119-126
Ascochyta/legume interactions are attractive systems for addressing evolutionary questions about the role of host specificity in fungal
speciation because many wild and cultivated cool season food legumes are infected by Ascochyta spp. and most of these fungi have described teleomorphs (Didymella spp.) that can be induced in the laboratory. Recent multilocus phylogenetic analyses of a worldwide sample of Ascochyta fungi causing ascochyta blights of chickpea (Cicer arietinum), faba bean (Vicia faba), lentil (Lens culinaris), and pea (Pisum sativum) have revealed that fungi causing disease on each host formed a monophyletic group. Host inoculations of these fungi demonstrated
that they were host-specific, causing disease only on the host species from which they were isolated. In contrast to the strict
association between monophyletic group and host observed for pathogens of cultivated legumes, Ascochyta fungi causing disease on wild bigflower vetch (Vicia grandiflora) were polyphyletic. Genetic crosses between several pairs of closely related, host-specific, and phylogenetically distinct
Ascochyta fungi were fully sexually compatible. Progeny from these crosses had normal cultural morphology and segregation of molecular
markers indicating a lack of intrinsic, post-zygotic mating barriers between the parental taxa. However, when progeny from
a cross between a faba bean-adapted isolate (A. fabae) and a pea-adapted isolate (A. pisi) were assessed for their pathogenicity to the parental hosts, almost all progeny were non-pathogenic to either faba bean
or pea. These results suggest that although these fungi have retained the ability to mate and produce progeny with normal
saprophytic fitness, progeny are severely compromised in parasitic fitness. The host specificity of these fungi, coupled with
the inability of hybrid progeny to colonize and reproduce on a host, may constitute strong extrinsic, pre-zygotic and post-zygotic
mating barriers in these fungi and promote the genetic isolation and speciation of host-specific taxa. A phylogeny of the
host plants is also being developed, and with more extensive sampling of pathogens and hosts from sympatric populations in
the centre of origin, the hypothesis of cospeciation of pathogens and hosts will be tested. The objectives of this review
are: (1) to summarize recent phylogenetic, host specificity and speciation studies of Ascochyta fungi, and (2) to suggest how current and future research using these pathosystems may lead to a better understanding of
the role of host specificity in the speciation of plant-pathogenic fungi and the cospeciation of pathogens and their hosts. 相似文献
18.
Twenty-four isolates of Fusarium oxysporum f. sp. ciceris were isolated from wilted chickpea plants obtained from different districts and ‘wilt sickplots’ of central Ethiopia to assess variability in pathogenecity of the populations. Each isolate was tested on 10 different chickpea lines and eight improved chickpea varieties. Isolates showed highly significant variation in wilt severity on the differential lines and improved varieties. Based on the reaction types induced on differential lines, isolates were grouped into four corresponding races. Of the 24 isolates, F13, F20 and F22 were the most virulent. Isolates of race 3 were found in all of the districts and ‘wilt sickplots’ studied. Improved chickpea varieties also showed differential reactions to the isolates. All varieties were resistant to isolates of race 3, while varieties Arerti and DZ-10-4 were resistant to all isolates tested, showing the lowest mean wilt severity. Varieties DZ-10-11 and Maryie were susceptible to isolates F13, F20 and F22 and showed the highest mean wilt severity. Identification of races can be useful in breeding chickpea varieties resistant to wilt. The differential reactions of the improved varieties against different races might be important in managing chickpea wilt through gene deployment. 相似文献
19.
20.
ABSTRACT The heterothallic ascomycete Nectria haematococca mating population VI (anamorph Fusarium solani) is a broad host range pathogen. Field isolates of this fungus that are pathogenic on pea tend to be female sterile, of low fertility, and the same mating type (MAT-1), whereas female fertile isolates of either mating type that are highly fertile tend to be nonpathogenic on this plant. To facilitate genetic analysis of traits that may be important in the ability of N. haematococca to parasitize peas, a breeding project was undertaken to produce hermaphroditic isolates of each mating type that are highly fertile and highly virulent on peas. Although the association of high virulence on peas with female sterility and the MAT-1 mating type was not completely broken, isolates with high fertility and high virulence on peas were bred within two generations. Highly virulent progeny were also isolated by an alternative method in which pea plants were inoculated with a mixture of ascospores from a cross between two moderately virulent parents. Whereas all ascospores isolated without selection in planta had lower virulence than the parents, many isolates recovered from diseased tissue were more virulent than the parental isolates. Some of the recovered isolates were shown by restriction fragment length polymorphism analysis to be genetic recombinants of the parents, demonstrating that the pea tissue selected virulent recombinants. All highly virulent isolates tested had the ability to detoxify the pea phytoalexin pisatin, again showing a link between this trait and pathogenicity on the pea. 相似文献