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1.
Infection by Pyrenophora teres f. teres (Ptt) or P. teres f. maculata (Ptm), the causal agents of the net and spot forms of net blotch of barley, respectively, can result in significant yield losses. The genetic structure of a collection of 128 Ptt and 92 Ptm isolates from the western Canadian provinces of Alberta (55 Ptt, 27 Ptm), Saskatchewan (58 Ptt, 46 Ptm) and Manitoba (15 Ptt, 19 Ptm) were analyzed by simple sequence repeat (SSR) marker analysis. Thirteen SSR loci were examined and found to be polymorphic within both Ptt and Ptm populations. In total, 110 distinct alleles were identified, with 19 of these shared between Ptt and Ptm, 75 specific to Ptt, and 16 specific to Ptm. Genotypic diversity was relatively high, with a clonal fraction of approximately 10 % within Ptt and Ptm populations. Significant genetic differentiation (PhiPT = 0.230, P = 0.001) was found among all populations; 77 % of genetic variation occurred within populations and 23 % between populations. Lower, but still significant genetic differentiation (PhiPT = 0.038, P = 0.001) was detected in Ptt, with 96 % of genetic variation occurring within populations. No significant genetic differentiation (PhiPT = 0.010, P = 0.177) was observed among Ptm populations. Isolates clustered in two distinct groups conforming to Ptt or Ptm, with no intermediate cluster. The high number of haplotypes observed, combined with an equal mating type ratio for both forms of the fungus, suggests that P. teres goes through regular cycles of sexual recombination in western Canada.  相似文献   

2.
Bacterial leaf/fruit spot and canker of stone fruits, caused by Xanthomonas arboricola pv. pruni, is a recurrent disease in Italy. A set of 23 strains has been isolated in peach and plum orchards in an intensively stone fruit cultivated area located in north-eastern Italy. They were all identified as X. arboricola pv. pruni by means of phytopathological and serological features: hypersensitive reaction on bean pods, pathogenicity test on immature peach or plum fruitlets, identification by immunofluorescence assay and conventional PCR. Phylogenetic analysis based on sequencing of the gyrB housekeeping gene of the isolates showed that they formed a unique clade, well characterised and separated from other xanthomonads. An insight into the genetic population features was attempted by rep-PCR analysis, using the ERIC, REP and BOX primers. The combined rep-PCR fingerprints showed a slight intra-pathovar variation within our isolates, which grouped in five close clusters. Copper resistance has been assessed in vitro for our whole X. arboricola pv. pruni collection, highlighting that two isolates show a level of resistance in vitro up to 200 ppm of copper. Nonetheless, the copLAB gene cluster, present in many other species of Xanthomonads, was not detected in any isolate, confirming the presence of a still unknown mechanism of copper detoxification in our Xanthomonads arboricola pv. pruni tolerant/resistant strains.  相似文献   

3.
Bacterial blight (BB) of rice caused by Xanthomonas oryzae pv. oryzae (Xoo), remains a major production constraint in rice cultivation especially in irrigated and rainfed lowland ecosystems in India. The pathogen is highly dynamic in nature and knowledge on pathotype composition among the Xoo population is imperative for designing a scientific resistance breeding program. In this study, four hundred isolates of Xoo collected from diverse rice growing regions of India were analyzed for their virulence and genetic composition. Virulence profiling was carried out on a set of differentials consisting of 22 near isogenic lines (NILs) of IR24 possessing different BB resistance genes and their combinations along with the checks. It was observed that different NILs possessing single BB resistance gene were susceptible to about 59–94% of the Xoo isolates except IRBB 13 (containing BB resistance gene xa13), which showed susceptibility to about 35% of the isolates. Based on the reaction of the Xoo isolates on the differentials, they were categorized into 22 pathotypes. Among the 22 pathotypes, IXoPt-1 and IXoPt-2 were least virulent and IXoPt # 18–22 were highly virulent. Pathotype IXoPt-19 which was virulent on all single BB resistance genes except xa13 constituted the major pathotype (22.5% isolates) and was widely distributed throughout India (16 states). This was followed by pathotype IXoPt-22 (17.25%) which was virulent on all the NILs possessing single BB resistance genes. Molecular analysis was carried out using two outwardly directed primers complementary to sequence of IS1112, a repetitive element of Xoo. A high level of genetic polymorphism was detected among these isolates and the isolates were grouped into 12 major clusters. The data indicated complex nature of evolution of the Xoo pathotypes and there was no strong correlation between pathotypes and genetic clusters as each genetic cluster was composed of Xoo isolates belonging to different pathotypes. The study indicated that none of the single BB resistance genes can provide broad spectrum resistance in India. However, two-gene combinations like xa5 + xa13 and different 3 or 4 genes combination like Xa4 + xa5 + xa13, Xa4 + xa13 + Xa21, xa5 + xa13 + Xa21 and Xa4 + xa5 + xa13 + Xa21 are broadly effective throughout India.  相似文献   

4.
Fusarium oxysporum f. sp. melongenae (Fomg), causal agent of Fusarium wilt of eggplant, is a serious pathogen in open fields and greenhouses. Inter-simple sequence repeat (ISSR) banding profiles, sequence analyses of inter-transcribed-spacer (ITS), translation elongation factor 1-alpha (TEF-1α), and actin (actA) DNA regions were employed in this study to determine genetic diversity and population structure of Fomg isolates obtained from Turkey. For ISSR study, (ACTG)5, (GACAC)3, (GACA)4, (GATA)4, HVH(TG)7 and (CA)8RG primers were selected from a set of 16. Discriminative ability of the primers revealed with various indices including polymorphic information content (PIC), and mean PIC value was calculated as 0.26. The ISSR data revealed 31 loci belonging to 202 Fomg isolates and 14 of them were found to be polymorphic. The isolates on neighbor joining ISSR tree were grouped into two major clusters which separated Fomg and outgroup isolates. Population structure was investigated based on bayesian modeling and results indicated five subpopulations (K = 5, ?K = 205.42). Mean genetic and geographical distances among sampling locations revealed only a weak and insignificant correlation (r = 0.583, P = 0.06). Phylogenetic analyses were carried out with ITS, TEF-1α and actA DNA regions with a selected subset of 30 Fomg, along with one non-host and one outgroup isolates. Since ITS region were not able to provide a meaningful separation, TEF-1α and actA sequences of each organism were concatenated individually to build a dendrogram. The clustering tree successfully separated the Fomg, non-host and outgroup isolates in which all Fomg were located on the same branch, forming a monophyletic group in the dendrogram.  相似文献   

5.
Genetic variability within Septoria carvi isolates obtained from various organs of caraway cultivated in south-eastern and central Poland was studied using the RAPD-PCR technique. The tests were performed using randomly selected primers. The DNA profiles obtained using four primers proved useful in determining genetic variability among the genotypes of Septoria carvi isolates. The present study characterized the differences in the nucleotide sequence within the internal transcribed spacer region of rDNA (ITS1, 5.8S, ITS2) of selected S. carvi isolates and reference strains of Septoria spp. Moreover, eight isolates were sequenced for three loci: actin, calmodulin and translation elongation factor 1-alpha, and the obtained sequences were compared with the sequences of Septoria reference strains affecting other plants of the family Apiaceae. Phylogenetic analysis showed distinct differences of the tested isolates, which allowed to treat them Septoria carvi species affecting the above-ground organs of caraway Carum carvi L. This study is the first report on the genetic characteristics of the species S. carvi.  相似文献   

6.
A survey was conducted in 16 fields cultivated with broad bean (Vicia faba L.) and garden pea (Pisum sativum L.) in nine localities of Apulia, southern Italy, to determine whether annual weeds were susceptible to the pea cyst nematode (PEACN), Heterodera goettingiana, and could therefore serve as alternate host for the nematode. The results of this study showed that black medick (Medicago lupulina L.) is a good host for the nematode increasing its population levels in the soil in the absence of the primary hosts. The identity of the PEACN was confirmed by integrative taxonomic approaches (classical, and molecular), resulting identical in all cases (broad bean and garden pea, as well as the spontaneous black medick infections). The phylogenetic analyses using ITS and coxI gene regions strongly support the identification of the populations of H. goettingiana from Italy. Also, ITS and coxI gene sequences were obtained from the same cyst, confirming the species identity in comparison to other nematodes and populations in the Goettingiana group, demonstrating that ITS and coxI gene regions of the PEACN are suitable molecular markers for accurate and unequivocal identification of the PEACN. Reproduction and histopathological analyses demonstrated a good host-suitability of black medick to the PEACN. This record enlarges the relatively narrow host-range of the pea cyst nematode and indicates the need to control M. lupulina to avoid the increase of the nematode population in the absence of the main host crop.  相似文献   

7.
Olive knot disease in Japan was first reported in Shizuoka Prefecture in 2014, and the causal agent was identified as Pseudomonas savastanoi pv. savastanoi. Subsequently, olive trees having knots were also found in Aichi and Kanagawa Prefectures in 2015, and the isolates from knots were also suspected to be P. savastanoi pv. savastanoi through preliminary examinations. Therefore, the Aichi and Kanagawa isolates were identified through comparison of isolates from three prefectures. Phylogenic analysis based on 16S rDNA and housekeeping genes (gyrB, rpoD, gltA and gap1) revealed that the isolates belonged to the same cluster as the pathotype strain, ICMP4352PT. The iaaM, H and L genes, which are involved in promotion of symptoms, and the ina gene coding the ice nucleation protein, were detected by PCR from all the isolates. In rep-PCR (ERIC and REP) analyses, the isolates yielded DNA fragment-banding patterns that were nearly identical to that of ICMP4352PT, but slight variations in banding patterns were observed among them. In a pathogenicity test, the isolates formed distinct knots on olive and pink jasmine. Phenotypic properties of the isolates were almost identical to those of ICMP4352PT, with the exception of d-sorbitol utilization. Consequently, Aichi and Kanagawa isolates from olive were identified as P. savastanoi pv. savastanoi, and several genetic diversities in terms of rep-PCR were found in the Japanese population of P. savastanoi pv. savastanoi, indicating their heterogeneity.  相似文献   

8.
The complex of Diaporthe (asexual morph) species occurring on soybean constitutes an important pathogenic group associated with diseases such as pod and stem blight, seed decay and stem canker. Stem canker, caused by Diaporthe aspalathi, has been reported as the most aggressive form of canker and its occurrence has limited soybean crop productivity in the southern United States. The main form of pathogen control is the use of stem canker resistant soybean varieties. In this study, strains of Diaporthe and Phomopsis were isolated from stem and seeds of soybean in different locations in South America during the years 1989–2014. Genomic DNA from 26 isolates were analyzed by PCR-restriction fragment length polymorphism (RFLP) and Amplified Fragment Length Polymorphism (AFLP) techniques, and sequencing of internal transcribed spacer (ITS) regions of ribosomal DNA. The molecular analysis of ITS sequences by alignment with those of ex-type strains deposited in GenBank and morphological characteristics allowed the identification of Phomopsis longicolla, D. phaseolorum var. sojae, D. caulivora and D. aspalathi. An analysis of the pathogenicity of 13 isolates of D. aspalathi inoculated in soybean genotypes carrying different resistance genes to stem canker (Rdm1, Rdm2, Rdm3, Rdm4, Rdm5 and Rdm?) enabled us to identify the occurrence of at least three races of D. aspalathi occurring in Brazil. Among the isolates identified as D. aspalathi, both molecular and phenotypic analyses showed clustering depending on the date of collection and pathogenicity, which revealed the existence of variability of the pathogen.  相似文献   

9.
Two Fusarium strains, isolated from Asparagus in Italy and Musa in Vietnam respectively, proved to be members of an undescribed clade within the Fusarium solani species complex based on phylogenetic species recognition on ITS, partial RPB2 and EF-1α gene fragments. Macro- and micro-morphological investigations followed with physiological studies done on this new species: Fusarium ershadii sp. nov can be distinguished by its conidial morphology. Both isolates of Fusarium ershadii were shown to be pathogenic to the monocot Asparagus officinalis when inoculated on roots and induced hollow root symptoms within two weeks in Asparagus officinalis seedlings. In comparison mild disease symptoms were observed by the same strains on Musa acuminata seedlings.  相似文献   

10.
Competitive effects between Fusarium graminearum, causing Fusarium head blight, and the endophyte Epicoccum nigrum, were performed in in vitro competition assays between the two species. Two E. nigrum isolates were isolated from wheat grains and tested as competitors against two F. graminearum isolates. A dual petri dish assay showed that E. nigrum reduced the mycelial growth of F. graminearum and vice versa. A glass slide assay revealed that E. nigrum crude cultural filtrate also had reducing effect on the growth of F. graminearum comparable to that of E. nigrum spore suspensions. Microscopy showed hyphae of F. graminearum and E. nigrum with many side branches when in close proximity, in contrast to pronounced apical hyphal growth when growing alone. Combinations of F. graminearum and E. nigrum on sterilised wheat grains were studied over time by qPCR. F. graminearum biomass was significantly reduced in inoculations applying E. nigrum three days prior to F. graminearum. In conclusion, these results showed competition and mycelial behaviour effects between F. graminearum and E. nigrum and support that E. nigrum may have potential to reduce F. graminearum infections in wheat. Competition experiments should be carried out in planta to study the interaction further.  相似文献   

11.
The virulence spectrum of 300 isolates of Xanthomonas oryzae pv. oryzae (Xoo), representing 17 districts of Punjab, Pakistan was elucidated through inoculation on a set of six rice IRRI-differentials. The virulence level was assessed by using principal component and cluster analysis. Among six principal components (PCs), PC-1 exhibited 59.3 % of the total variance. The highly virulent isolates clusters on the positive side of the ordination away from the point of intersection of PC1 and PC2 and classifies the Xoo isolates from slow disease to the highest disease causing entities. The 300 isolates were categorized into 29 pathotypes (Pt1-29) wherein the highly virulent pathotype (Pt-1), comprises of 39 Xoo isolates were widespread in 12 districts. The majority of Xoo isolates were moderately to least virulent (21.7–43 %) and average disease progress curves confirmed the field reactions of these pathotype clusters for an efficient recognition of Xoo isolates. Interaction of the pathogen with differentials harboring different resistant genes was well investigated in the current study for future management approaches for which the surveillance of the new Xoo pathotypes may expedite the disease resistant rice breeding programme in the country.  相似文献   

12.
Aureobasidium isolated from Vitis vinifera (cv Chardonnay) grapevine tissues were characterised using morphological and molecular techniques. Species level identification of 29 isolates was accomplished by partial amplification and sequencing of the ITS region (ITS1–5.8S–ITS2) using universal primers ITS1 and ITS4. A comparison of nucleotide sequences using BLAST followed by phylogenetic analysis revealed that all isolates examined were Aureobasidium pullulans. Strain level discrimination of a total of 100 epiphytic Aureobasidium isolates including three reference strains was successfully carried out using two inter simple sequence repeat (ISSR) primers, (AAC)5 and (GTG)5 and the Intron Splice Junction R1 (ISJ-R1) primer in which 24, 24 and 15 scorable bands were produced for each primer, respectively. The high level of genetic variation recorded among the isolates further highlighted the high levels of strain diversity among A. pullulans residing on grapevines. Thirty-two epiphytic Aureobasidium isolates were examined for their ability to inhibit the growth of Greeneria uvicola, responsible for bitter rot of grapes. Using an in-vitro dual-culture antagonism assay, all isolates inhibited the growth of G. uvicola (Isolates DAR 77272 and DAR 77273) with inhibition ranging from 15 to 85%. Three Aureobasidium isolates were then examined for their ability to inhibit G. uvicola when co-inoculated onto detached berries, leaves and grape bunches growing on potted vines in a glass house. All isolates reduced the severity of bitter rot infection. The results indicate that A. pullulans has the potential to suppress bitter rot of grapes.  相似文献   

13.
Arabidopsis thaliana exhibits a durable resistance called nonhost resistance against nonadapted fungal pathogens. A. thaliana activates preinvasive resistance and terminates entry attempts by nonadapted fungi belonging to the genus Colletotrichum, which cause anthracnose disease in many plants. In the interaction between A. thaliana and nonadapted C. tropicale, the preinvasive resistance involves the PENETRATION 2-related antifungal secondary metabolite pathway and the ENHANCED DISEASE RESISTANCE 1-dependent antifungal peptide pathway. The development of invasive hyphae by C. tropicale owing to the reduction of preinvasive resistance then triggers the blockage of further hyphal expansion via the activation of the second layer of resistance, i.e., postinvasive resistance, which guarantees the robustness of the nonhost resistance of A. thaliana against Colletotrichum pathogens. Both the tryptophan-derived metabolic pathway and glutathione synthesis play critical roles in the postinvasive resistance against C. tropicale, although the molecular mechanism of postinvasive resistance remains to be elucidated. In this review, we describe the current understanding of the molecular background of the Arabidopsis nonhost resistance against Colletotrichum fungi and discuss perspectives for future research on this durable resistance.  相似文献   

14.
Monilinia fructicola, the most destructive pathogen of the genus Monilinia, has recently been introduced into Serbia and many other European countries. Since then, many studies have been conducted to evaluate the characteristics of Monilinia species that have a role in the establishment and survival of the pathogen in new areas. The present study assessed the capacity of M. fructicola to repress and replace Monilinia laxa in Serbia based on: fungicide sensitivity, growth rate and aggressiveness at different temperatures, as well as frost hardiness of the isolates of both species. The results showed that the isolates of M. fructicola, compared to M. laxa, were significantly less sensitive to the following fungicides: iprodione, tebucanozole, chlorothalonil, azoxystrobin, fluopyram, and boscalid. In addition, M. laxa isolates exhibited little variation in sensitivity to all of the tested fungicides, whereas M. fructicola isolates displayed a wide range of sensitivity. The temperature of 5°C favored M. laxa growth and aggressiveness, while at 30°C M. fructicola grew faster and had higher lesion expansion rate. These results support an assumption that M. fructicola will continue to spread in Serbian orchards in coming years, particularly on stone fruits harvested during hot summer weather.  相似文献   

15.
Tomato (Solanum lycopersicum L.) ARGINASE2 (ARG2) and THREONINE DEAMINASE2 (TD2) are involved in plant defense. These enzymes act in the midgut of herbivores fed on tomato plants to degrade the essential amino acids Arg and Thr, respectively. Although it has been demonstrated that overexpression of the SlARG2 gene in tomato enhanced its resistance against M. sexta larvae, knock-down the expression of SlTD2 reduced the resistance of tomato to lepidopteran herbivores; it remains unclear whether overexpression of SlTD2 could enhance the resistance of the host plants to herbivores, or whether combined overexpression of SlARG2 and SlTD2 could lead to synergistically enhanced resistance to insects. Here, we generated transgenic Arabidopsis plants overexpressing SlARG2 (SlARG2 OE) and SlTD2 (SlTD2 OE) individually as well as in combination (SlARG2-SlTD2 OE). Overexpression of these genes did not affect Arabidopsis development, seed yield, or Arg and Thr content. Insect-feeding bioassay was performed by feeding diamondback moth (Plutella xylostella L.) larvae on detached leaves of wild-type, SlARG2 OE, SlTD2 OE, and SlARG2-SlTD2 OE plants. Larvae fed on SlARG2 OE leaves showed approximately 31% to 35% reduction in weight and 6% to 10% reduction in survival rate compared to those fed on wild-type leaves. Although larvae fed on SlTD2 OE leaves showed no reduction in survival rate, they gained less weight. Whereas larvae fed on SlARG2-SlTD2 OE leaves showed neither reduction in weight nor reduction in survival rate. We further investigated the arginase enzymatic activity of the SlARG2 OE and SlARG2-SlTD2 OE transgenic plants. The SlARG2 OE line most resistant to diamondback moth larvae displayed the highest arginase activity. Our data indicate that overexpression of SlARG2 or SlTD2 in Arabidopsis can enhance its resistance against diamondback moth, whereas combined overexpression of SlARG2 and SlTD2 did not generate synergistically increased resistance to diamondback moth.  相似文献   

16.
Type IV pili of X. fastidiosa are regulated by pilG, a response regulator protein putatively involved in chemotaxis-like operon sensing stimuli through signal transduction pathways. To elucidate the roles of pilG in pathogenicity of X. fastidiosa, the pilG-deletion mutant XfΔpilG and complemented strain XfΔpilG-C were generated. While all strains had similar growth curves in vitro, XfΔpliG showed significant reduction in cell-matrix adherence and biofilm production compared with wild-type X. fastidiosa and XfΔpilG-C. The genes pilE, pilU, pilT, and pilS were down-regulated in XfΔpliG when compared with its complemented strain and wild-type X. fastidiosa. Finally, no Pierce’s disease symptoms were observed in grapevines inoculated with XfΔpilG, whereas grapevines inoculated with the wild-type X. fastidiosa and complemented strain of XfΔpilG-C developed typical Pierce’s Disease (PD) symptoms. The results indicate that pilG has a role in X. fastidiosa virulence in grapevines.  相似文献   

17.
Rhizoctonia solani AG1IA is an important fungal pathogen causing significant yield and quality losses in rice production. However, little is known about the levels of genetic diversity and structure of this pathogen in North India. Out of 240 samples collected from different rice-growing regions of North India, 112 isolates were identified as R. solani AG1IA subgroups using species-specific primers. All 112 isolates were organized into four groups on the basis of percent disease index (PDI). The majority of the isolates were weakly virulent. Population genetic analysis was performed within and between populations using inter simple sequence repeat (ISSR) markers. A total of 8249 alleles were identified from the 112 isolates of R. solani AG1IA through analysis of the ten inter simple sequence repeat markers. All the ten ISSR markers were polymorphic. The average number of bands per primer was 7.3 which ranged in size from 250 to 1500 bp. Genetic structure of the isolates using inter simple sequence repeat primers showed high degree of polymorphism (PIC ≥0.81). The analysis of molecular variance (AMOVA) indicated that most of the genetic diversity occurred within populations (60%), while the variability among populations and among regions contributed 25 and 15%, respectively. Overall, the present study reveals that a large variation exists among rice-infecting isolates of R. solani AG1IA in North India. Fingerprinting of the isolates using ISSRs along with phenotypic characterization and virulence analysis will help epidemiological studies that can provide new insights into pathogen biology and disease spread.  相似文献   

18.
The taxonomic assignment of Japanese potato blackleg isolates of Dickeya spp. has not been confirmed after the changes in their former name, Erwinia chrysanthemi. Therefore, we investigated and identified 23 representative isolates of Dickeya spp. from symptomatic stems of potatoes in Japan, with biochemical tests and phylogenetic sequence analysis using recA, dnaX, rpoD, gyrB, and 16S rDNA sequences. Results of our biochemical tests showed that all isolates can be assigned to phenon 5 and biovar 1, which are associated with D. dianthicola. Based on the recA, dnaX, rpoD, gyrB, and 16S rDNA sequences, all isolates are in the same clade with D. dianthicola and were clearly distinguished from D. chrysanthemi, D. dadantii, D. dadantii subsp. dieffenbachiae, D. solani, D. zeae, and D. paradisiaca. Therefore, we conclude that Dickeya spp. isolated from potatoes with blackleg symptoms in Japan are D. dianthicola.  相似文献   

19.
An extensive survey was carried out to collect Fusarium species colonizing the lower stems (crowns) of bread wheat (Triticum aestivum L.) and durum wheat (T. durum Desf.) from different wheat growing regions of Turkey in summer 2013. Samples were collected from 200 fields representing the major wheat cultivation areas in Turkey, and fungi were isolated from symptomatic crowns. The isolates were identified to species level by sequencing the translation elongation factor 1-alpha (TEF1-α) gene region using primers ef1 and ef2. A total of 339 isolates representing 17 Fusarium species were isolated. The isolates were identified as F. culmorum, F. pseudograminearum, F. graminearum, F. equiseti, F. acuminatum, F. brachygibbosum, F. hostae, F. redolens, F. avenaceum, F. oxysporum, F. torulosum, F. proliferatum, F. flocciferum, F. solani, F. incarnatum, F. tricinctum and F. reticulatum. Fusarium equiseti was the most commonly isolated species, accounting for 36% of the total Fusarium species isolated. Among the damaging species, F. culmorum was the predominant species being isolated from 13.6% of sites surveyed while F. pseudograminearum and F. graminearum were isolated only from 1% and 0.5% of surveyed sites, respectively. Six out of the 17 Fusarium species tested for pathogenicity caused crown rot with different levels of severity. Fusarium culmorum, F. pseudograminearum and F. graminearum caused severe crown rot disease on durum wheat. Fusarium avenaceum and F. hostae were weakly to moderately virulent. Fusarium redolens was weakly virulent. However, F. oxysporum, F. equiseti, F. solani, F. incarnatum, F. reticulatum, F. flocciferum, F. tricinctum, F. brachygibbosum, F. torulosum, F. acuminatum and F. proliferatum were non-pathogenic. The result of this study reveal the existence of a wide range of Fusarium species associated with crown rot of wheat in Turkey.  相似文献   

20.
Alternaria genus includes many plant pathogens on numerous hosts, causing leaf spots, rots and blights. Alternaria blight has been observed as one of the important fungal diseases of pistachio (Pistacia vera L.) as well as its wild relatives (P. terebinthus, P. lentiscus, P. khinjuk, P. atlantica, P. mutica) in Turkey. Alternaria species were sampled from Pistacia spp. hosts from different geographic regions in Turkey during field trips in late spring to early fall of 2013. Alternaria blight symptoms were observed mainly on fruits and rarely on leaves. Four hundred and twenty two of the isolates were morphologically defined as A. alternata, A. tenuissima, A. arborescens and also intermediate morpho-species between A. alternata/A. arborescens. Pathogenicity of the isolates was confirmed with host inoculations on detached fruits. Mating types of 270 isolates of Alternaria spp. from the collection were identified using a PCR-based mating type assay that amplifies either a MAT1-1 or a MAT1-2 fragment from the mating locus. Although a strongly clonal population structure was expected due to the putative asexual reproduction of these fungi, both idiomorphs were detected at equal frequencies at several different spatial scales. The distribution of mating types within each geographic region, within host species as well as in overall collection was not significantly different from 1:1. Amplified fragments of partial idiomorph sequences were obtained for representative isolates. Parsimony trees were depicted based on sequence data of mating type genes for these representative isolates as well as some other Alternaria species obtained by Genebank. Several point mutations presented a few clusters which are supported by high bootsrapped values. The Alternaria blight disease agents both from cultivated and wild hosts were pathogenic on pistachio which may cause difficulties to control the disease because of extensity of pathogen sources. Besides, equal mating type distribution of the pathogen at both geographic and host species levels suggests a potential for sexual reproduction of Alternaria spp. in Turkey.  相似文献   

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