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1.
The parasitic weed Orobanche cumana (sunflower broomrape) constrains sunflower production in eastern and southern Europe and in the Middle East. Although genetic resistance is the most effective control method, new parasite races evolve overcoming sunflower resistance. In this work, highly virulent populations of O. cumana were analysed for pathogenicity and genetic diversity. The virulence of 11 populations from Hungary, Romania, Spain and Turkey was assessed and compared after infection of sunflower inbred lines to differentiate races of the parasite under glasshouse conditions. Molecular diversity among and within 27 parasite populations was studied by RAPD‐PCR, UPGMA and amova analyses. Highly virulent race F was identified in Hungary, Spain and Turkey. The most virulent race (G) was also found in Turkey. The molecular analysis among highly virulent populations of O. cumana identified four molecular clusters, respectively, grouping populations from Central Spain, Hungary, South Spain and Turkey. The genetic homogeneity within parasite populations was confirmed, since no molecular divergences were found within them. This work constitutes the first geographical study of O. cumana together with pathogenicity and molecular traits inherent to each geographical group, and provides useful information for possible phylogenetic analyses of O. cumana. In addition, molecular markers associated with geographical origin could be developed and used as diagnostic tools to track new broomrape introductions into areas free of virulent races where they might represent a threat to sunflower production.  相似文献   

2.
Orobanche cumana is a weed that grows as a root parasite on sunflower. In general, the O. cumana–sunflower parasitic system is regarded to follow the gene‐for‐gene model, although this has never been demonstrated at the genetic level in O. cumana. The Or5 dominant gene in sunflower confers resistance to O. cumana race E, but not to race F. The objective of this research was to study the inheritance of avirulence/virulence in crosses between plants of O. cumana lines classified as races E and F. Four race E and three race F lines were developed, from which four race E × race F cross‐combinations were made, in three cases including reciprocals. In all cases, F1 seeds did not have the ability to parasitise sunflower line P‐1380 carrying the Or5 gene, indicating dominance of race E avirulence allele(s). Five F2 populations comprising a total of 387 F2:3 families were evaluated on sunflower line P‐1380. In all cases, one‐fourth of the F2:3 families did not possess the ability to parasitise P‐1380 plants, suggesting that race E avirulence and race F virulence on P‐1380 are allelic and controlled by a single locus. This study demonstrated the gene‐for‐gene interaction in the O. cumana–sunflower parasite system and provided useful information to identify genes involved in O. cumana virulence. The approach followed in this research can contribute to define precisely races of the parasite on the basis of the presence of avirulence genes.  相似文献   

3.
Different races of the parasitic Orobanche cumana (sunflower broomrape) have been reported in Spain, race F being the most virulent. Full resistance in sunflower to races A–E is achieved with each of the single major genes Or1 to Or5 respectively. However, parasitised hybrids allegedly resistant to race F were observed in early 2002. The purpose of this study was to verify broomrape incidences (BI) on resistant sunflower genotypes, to assess the mixture of races within field populations and to test for partial resistance to race F in the sunflower hybrids showing a low degree of attack (DA) by the weed. Tests were conducted under field conditions in two locations of southern Spain. While no significant differences were found for yield and BI between locations, the DA on the cultivars depended on the location. With high infection levels and significantly lower yield in susceptible controls, marked differences in BI and DA were found within resistant cultivars, but all of them showed similar crop yield. When artificially inoculated with several populations of race F, line P96 and mainly line L86, were consistently slightly infected, suggesting they were inbred lines responsible for horizontal resistance in infested fields. L86 was extremely susceptible to race E populations, which is unusual as sunflower resistance to one race provided resistance to all the previously described races of O. cumana. No different virulences were detected within two groups of subpopulations (races E and F) inoculated onto resistant sunflower genotypes. However, race F subpopulations showed significant differences in aggressiveness, which seems to be related to horizontal (multigenic) resistance of the crop to the parasitic weed.  相似文献   

4.
Orobanche cumana (broomrape) is a severe constraint to sunflower production in southern and eastern Europe and the Middle East. Races A to E of this parasitic weed controlled by genes Or1 to Or5 have been described. A study of 38 seed accessions of O. cumana collected from different locations in Spain between 1983 and 2003 investigated the effect of long‐term storage in the laboratory on germination and infectivity and assessed their virulence on a number of sunflower cultivars. Only 18 infected the susceptible cultivar B117. Infectivity was maintained for up to 17 years of storage, but with a greatly decreased vigour as compared with that of recently collected seed. The 12 oldest viable accessions overcame the resistance of the gene Or5 (in resistant line NR5). Seven out of them, in particular those collected in 1988 and 1989, were identified as race F. Three accessions were identified as race E allegedly holding components of higher virulence. Our results show evidence of the occurrence of race F prior to the use of sunflower hybrids resistant to race E, suggesting the former as indigenous to the country. This finding suggests the necessity of a continuous breeding of sunflower for resistance to O. cumana. The effectiveness and sustainability of genetic resistance must rely on the knowledge of the diverse virulence characteristics of O. cumana accessions.  相似文献   

5.
We present the results of a histochemical study comparing seedlings of races C and D of Orobanche cumana Wallr. (syn. O. cernua Loefl.) attacking sunflower (Helianthus annuus L.) in southern Russia. Three groups of O. cumana seedlings were distinguished according to the peroxidase content of the cells in the radicles: (1) those with neither extracellular nor intracellubr peroxidase and whose radicles have a smooth apex (these were classified as non-infective): (2) those with a high peroxidase content of the nuclei and the cytoplasm layer adjacent to the cell wall, as well as excretion of peroxidase from the apex of the radicles: (3) those with a similarly high peroxidase activity in the parasite cells, but without extracellular excretion. The apices of the radicles of the last two groups are swollen. It is suggested that these belong to O. cumana races C and D respectively. The extracellular peroxidase in O. cumana race C reacts with phenolic compounds, which are lignin precursors of the host, resulting in host resistance due to the formation of lignin layers in sunflowers possessing the Or3 gene for resistance. The absence of extracellular peroxidase in O. cumana race D prevents lignin formation and enables the parasite to attach to the host vascular system. Comparison of these data with the information on the earlier O. cumana races A and B, and older sunflower cultivars, points to a crucial role of peroxidase in the process of breeding new sunflower cultivars and the evolution of new O. cumana races.  相似文献   

6.
Orobanche cumana is an obligate root parasite of sunflower. It represents a major agricultural problem in many countries of southern and eastern Europe. Information on O. cumana population genetics, structure and dynamics is scarce, particularly due to the lack of suitable molecular markers for such studies. The objective of this study was to identify and characterise simple sequence repeat (SSR) markers for O. cumana. Four thousand two hundred SSR‐containing candidate sequences were obtained from O. cumana using next‐generation sequencing, from which 298 SSR primer pairs were designed and 217 of them used for validation. Seventy nine SSR primers produced reproducible, high quality amplicons of the expected size that were polymorphic among 18 O. cumana populations from different geographical locations and hosts (sunflower, wild hosts from the Compositae family). The number of alleles per locus ranged from 2 to 10, with an average polymorphism information content value of 0.37. The O. cumana SSR markers were highly transferable to the closely related species Orobanche cernua. SSR markers showed high resolving power; UPGMA cluster analysis allowed proper classification of Orobanche spp. samples into species (O. cumana and O. cernua), geographical origin and host. The functional SSR markers reported in this study constitute a valuable tool for genetic analyses in O. cumana and related species and will contribute insights into the biology and genetics of this parasitic weed.  相似文献   

7.
Summary Orobanche species are commonly identified using morphological characteristics. In many cases, the distinction of closely related species is difficult, and a molecular tool is more suitable to differentiate them. In this study, genomic polymorphism between morphologically distinct species was investigated through amplification by polymerase chain reaction (PCR) of intersimple sequence repeat (ISSR) regions. Five primers were used to study genetic variation in the morphologically distinct species O. hederae and O. amethystea, as well as the closely related species O. cernua and O. cumana. For the first two species, all the primers detected genetic polymorphism. Anchored primers allowed the identification of more specific molecular markers than non‐anchored tri‐ and tetranucleotide primers. Genetic polymorphism was investigated among three O. hederae populations using the two types of primer. One non‐anchored and two anchored primers detected intraspecific variation, which was not correlated with the geographical location of those populations. The primer (GATA)4 detected polymorphism between five specimens each of O. cernua and O. cumana species collected from different countries, permitting these two closely related species to be clearly differentiated. This study demonstrated that ISSR markers can be highly reliable for precise identification of Orobanche species.  相似文献   

8.
Thirty-six populations of the potato cyst nematodeGlobodera pallida, all collected in the Netherlands, were analysed twice: by two-dimensional gel electrophoresis of proteins (2-DGE) and by random amplified polymorphic DNA fingerprinting (RAPD). Two-DGE revealed frequencies of 21 alleles at eight putative loci in each population. The same populations were subjected to RAPD analysis. This qualitative technique revealed 38 polymorphic DNA fragments. Both datasets were independently processed to determine the intraspecific variation. UPGMA analysis resulted in a 2-DGE- and a RAPD-based dendrogram with cophenetic correlation coefficients of 0.755 and 0.838 respectively. The correlation between the genetic similarity values for the populations was 0.572. Comparison between the 2-DGE- and the RAPD-based dendrogram revealed that only thirteen of the 36 populations analysed were clustered identically. It is concluded that the gene pool similarity concept is only in some instances applicable to Dutch populations ofG. pallida. For populations that could not be differentiated unequivocally on the basis of molecular markers, markers closely linked to avirulence genes should be identified. Approaches that will lead to the identification of such markers are discussed.  相似文献   

9.
X Guo  M Ren  J Ding 《Weed Research》2016,56(6):442-451
Many invasive plants have long been suspected of firstly being introduced and cultivated by a local botanical garden or nursery and then escaping into the field after adapting to the novel environment. The role of botanical gardens in the spread of invasive plants has not yet been explored experimentally. In this article, we studied the possible roles of two botanical gardens in the spread of invasive Solidago canadensis (Asterceae) in China by analysing genetic relationships of invasive and native (United States) populations with intersimple sequence repeats markers. Our results showed a high genetic variation (mean He = 0.292) and a large proportion of genetic variation (85.6%) residing within populations. Solidago canadensis was possibly introduced firstly into eastern China. The plants from Lushan Botanical Garden showed distant genetic distance from all of the other populations, suggesting that this botanical garden had little effect on the invasion of S. canadensis. Populations from Wuhan Botanical Garden in central China, however, showed close genetic relationships with local populations and populations in west and south‐west China, suggesting gene exchange between these populations. Thus, risk assessment is critical for plant introduction and conservation, as introductions of alien plants by botanical gardens may facilitate plant invasions, while plants conserved in botanical gardens may be at risk by surrounding plant invasions.  相似文献   

10.
Since 1911, dothistroma needle blight, caused by Dothistroma septosporum, has been recorded in most European countries. In the Czech Republic, the fungus has become an important disease of pines since 2000, especially Austrian pines in plantations of Christmas and ornamental trees. The aim of this study was to analyse the population structure, gene flow and mode of reproduction of this pathogen. Microsatellite and mating‐type markers were analysed in a Dothistroma population in the southeastern part of the country using reference isolates from other European countries. The haplotypic diversity was high, with 87 unique and 13 shared haplotypes (probable clones) identified in 121 samples. Based on structure analysis, the isolates were divided into two populations, with an uneven distribution over the sampling sites. The grouping of the sites to the populations did not follow a geographical pattern because certain isolates that were sympatrically co‐occurring at the same site were placed in different populations. Tests for random mating (the index of association and a parsimony tree‐length permutation test) showed a significant clonal mode of reproduction in most cases, but the intrapopulation haplotypic diversity is unexpectedly high. Although a teleomorphic stage of D. septosporum has not been previously observed in the Czech Republic, the high intrapopulation haplotypic diversity can be explained by infrequent sexual reproduction consistent with the occurrence of both mating types.  相似文献   

11.
Qi L  Gulya T  Seiler GJ  Hulke BS  Vick BA 《Phytopathology》2011,101(2):241-249
Sunflower rust, caused by Puccinia helianthi, is a prevalent disease in many countries throughout the world. The U.S. Department of Agriculture (USDA)-Agricultural Research Service, Sunflower Research Unit has released rust resistant breeding materials for several decades. However, constantly coevolving rust populations have formed new virulent races to which current hybrids have little resistance. The objectives of this study were to identify resistance to race 336, the predominant race in North America, and to race 777, the most virulent race currently known, and to validate molecular markers known to be linked to rust resistance genes in the sunflower gene pool. A total of 104 entries, including 66 released USDA inbred lines, 14 USDA interspecific germplasm lines, and 24 foreign germplasms, all developed specifically for rust resistance, were tested for their reaction to races 336 and 777. Only 13 of the 104 entries tested were resistant to both races, whereas another six were resistant only to race 336. The interspecific germplasm line, Rf ANN-1742, was resistant to both races and was identified as a new rust resistance source. A selection of 24 lines including 19 lines resistant to races 777 and/or 336 was screened with DNA markers linked to rust resistance genes R(1), R(2), R(4u), and R(5). The results indicated that the existing resistant lines are diverse in rust resistance genes. Durable genetic resistance through gene pyramiding will be effective for the control of rust.  相似文献   

12.
Some species of the genusOrobanche are among the most devastating parasitic weeds, causing extensive damage in agricultural fields. Considering the difficult control due to seed longevity in the soil, small seed size, high fecundity and a subterranean phase that allows them to parasitize the host before they emerge and become evident, the development of diagnostic markers is highly recommended. In our study we identified potential molecular diagnostic markers from the plastid genome in order to distinguish among the most importantOrobanche species attacking crops in Andalusia, the southern region of the Iberian Peninsula. The study has consideredO. crenata, O ramosa andO. cumana causing serious losses in legumes, solanaceous crops and sunflower fields, respectively, andO. minor that, although abundant in Andalusia, has to our knowledge not yet been found parasitizing agricultural hosts. We amplified a non-coding region from the plastid genome, studied sequence differences among the amplified fragments and digested those of the same length with selected restriction enzymes. Here, we propose a molecular protocol to distinguish the main parasitic plants in crop fields of southern Spain. Different applications such as identification ofOrobanche seeds in soil or crop seed lots are discussed in order to offer right crop recommendations or to prevent new infestation of parasite-free fields. Recommendations for further development of these diagnostic markers are also considered. http://www.phytoparasitica.org posting Jan. 15, 2007.  相似文献   

13.
We developed 20 microsatellite markers to genotype over 100 populations of the parasitic weed Phelipanche ramosa, which covers a wide host crop and geographic range. A representative core collection of 15 populations was also used in cross‐infestation assays to study host preference during germination, attachment and shoot formation. We observed low genetic differentiation within most of the populations, but high genetic differentiation between populations partitioned into 3 genetic groups with different host preferences and geographic distributions. Genetic group 1 is detected exclusively in western France and on various host crops, notably winter oilseed rape (WOSR) and not hemp. Cross‐infection assays confirmed its incompatibility with hemp and showed its preference for WOSR and tobacco in terms of germination and attachment success. The group 2 populations share a large geographic distribution in France and Europe, low germination success with WOSR and high germination success, attachment success and shoot formation with hemp, tobacco or tomato. The subclades 2a and 2b include most of the French populations in hemp crops in eastern France and in tobacco fields in several European countries respectively. The genetic analyses revealed the potential of the three groups to increase their geographic range in the future. Intermediate genetic groups showed higher intrapopulation diversity and represent potential stocks for new host race emergence. Those findings argue in favour of the existence of host races in P. ramosa and should be considered for appropriate management strategies, notably in breeding programmes for resistance against this parasitic weed.  相似文献   

14.
Restriction fragment length polymorphism (RFLP) markers were used to assess the genetic structure of populations of Mycosphaerella graminicola collected from wheat fields. A total of 585 isolates representing 10 field populations were sampled from Iran, Argentina and Australia. The genetic structure of M. graminicola populations from Iran and Argentina is described for the first time. Results were compared to previously investigated populations from Israel, Uruguay and Australia. Populations from Iran exhibited high clonality and low gene diversity, suggesting an inoculation event. Populations from uninoculated fields in Argentina had gene and genotype diversities similar to previously described European and North American populations. Genotype diversity was high for populations from Australia and tests for multilocus associations were consistent with sexual recombination in these populations. Gene diversity was low and fixed alleles were found for several loci. These findings are consistent with a relatively small founding population for Australia. These 10 new populations were integrated into a genetic distance comparison with 13 global populations that were characterized earlier.  相似文献   

15.
BACKGROUND: There is great concern about the high losses and strong depopulation of honey bee colonies in some areas of Spain. Some beekeepers have suggested that sunflower seeds treated with the insecticide fipronil could be an important factor in causing those losses. Therefore, an in‐depth field study has been carried out in two regions of Spain where sunflower production is intense (Cuenca and Andalucía) and where, for some crops and varieties, fipronil has been used as seed insecticide. RESULTS: Samples of adult bees and pollen were analysed for bee pathogens and pesticide residues respectively. Neither fipronil residues nor its metabolites were detected in any of the samples analysed, indicating that short‐term or chronic exposure of bees to fipronil and/or its metabolites can be ruled out in the apiaries surveyed. Varroa destructor and Nosema ceranae were found to be very prevalent. CONCLUSION: The combination of the two pathogens could augment the risk of colony death in infected colonies, without fipronil residues exerting a significant effect in the given field conditions. Indeed, in this study the losses observed in apiaries located close to sunflower crops were similar to those in apiaries situated in forested areas with wild vegetation. Copyright © 2011 Society of Chemical Industry  相似文献   

16.
向日葵上一种列当的发生分布及防治   总被引：1，自引：0，他引：1  
从1979～1980年调查研究明确了吉林省白城地区寄生在向日葵上的恶性杂草——列当的种名是Orobanche coerulescens Steph(本文暂称白城列当)而不是向日葵列当(O.cumana)。白城列当在全地区8个县均有分布,发生密度较大的地块1平方米均有300棵左右,寄生株率96%以上,1株向日葵上最多寄生146棵。其垂直分布主要在土壤耕层里,是寄生于向日葵根部,以5～15厘米耕层寄生率最高达93%。在向日葵植株周围的水平分布以距向日葵5～20厘米寄生率达68.1%。被害的向日葵植株,表现株矮、茎细、盘小,甚至全株枯死。籽实减产38.3～70.3%,籽仁含油率降低3.3～17.9%,严重影响向日葵的生产,应引起各方面重视。提出因地制宜地采取选育抗性品种,合理轮作及提早铲除等综合防治措施,以便尽早地消灭在始发阶段。  相似文献   

17.
BACKGROUND: Before its introduction into Europe at the end of 2006, Tuta absoluta (Povolny, 1994) was confined solely to South America. Currently, this invasive pest is well established in various European and Mediterranean countries, causing important economic losses to tomato (Lycopersicon esculentum Mill.) crops. In order to study the genetic variability of this pest, 23 Mediterranean and ten native South American populations were analysed with nuclear ribosomal DNA (rDNA) and mitochondrial DNA (mtDNA) markers. RESULTS: The internal transcribed spacers 1 (ITS1) and 2 (ITS2) of rDNA and a fragment in the mtDNA gene encoding cytochrome oxidase I (COI) were PCR amplified and sequenced in T. absoluta. Sequence analyses consistently revealed neither intrapopulation nor interpopulation variation in either genomic region. CONCLUSIONS: High genetic homogeneity was detected in T. absoluta populations from the Mediterranean Basin and South America, based on mtCOI and ITS rDNA sequence analysis. A single genetic type was identified in this pest. Copyright © 2011 Society of Chemical Industry  相似文献   

18.
Wheat stem rust, caused by Puccinia graminis f. sp. tritici, is a re-emerging disease, posing a threat to wheat production. In Spain, stem rust has been rarely detected since the 1970s, but infection was observed in wheat fields in 2018. We analysed six stem rust samples collected in Rota, Cádiz province and one from Monteagudo del Castillo, Teruel province. All the samples from Rota were typed as race TKTTF, whereas the sample from Monteagudo del Castillo, collected in a wheat field adjacent to barberry bushes, was typed as race TKHBK. This race has a unique and significant virulence combination that includes virulence to Sr31, Sr33, Sr53 and Sr59, and is avirulent to Rusty, a durum line developed for universal susceptibility to the wheat stem rust pathogen. TKHBK is the first race outside the Ug99 race group with virulence to Sr31 and the first known race with virulence to Sr59. Genotyping studies indicate that race TKHBK does not belong to the Ug99 or TKTTF race groups and constitutes a previously unknown lineage. Two hundred bread and durum wheat cultivars and breeding lines from Spain were evaluated against TKHBK, TKTTF, and six additional races. Resistance was observed to all the races evaluated. Molecular markers confirmed the presence of Sr7a, Sr24, Sr31, Sr38 and Sr57 in bread wheat, and Sr13 in durum wheat. The re-emergence of wheat stem rust in Spain and the occurrence of unique virulences underscore the need to continue surveying and monitoring this disease.  相似文献   

19.
This study investigated inter-simple sequence repeat (ISSR), vegetative compatibility, and aggressiveness diversity in 101 isolates of Diplodia bulgarica recovered from apple trees displaying symptoms of canker and decline in West Azarbaijan province of Iran. Marker analyses revealed high within population diversity, low genetic differentiation, high gene flow, and sharing of multilocus genotypes (MLGs) among geographic populations. Moreover, clustering and multivariate analyses identified two highly differentiated genetic clusters with limited admixture between them. These findings may suggest that the pathogen has been introduced from two genetically divergent sources and has been moved within the region through infected materials. The large number of MLGs, low clonal fraction, and absence of a widely distributed dominant genotype may explain the occurrence of recombination in this pathogen. However, significant linkage disequilibrium in the populations and limited admixture between genetic clusters may indicate the rare occurrence of recombination in D. bulgarica populations in West Azarbaijan, and that the pathogen has not been in the province long enough to reach equilibrium. Vegetative compatibility analyses revealed the occurrence of anastomosis between nonself pairings and high vegetative compatibility group diversity within populations. All studied MLGs produced necrotic lesions on detached shoots of Red Delicious apple but differed in their aggressiveness levels. Our results provide new insights into genetic and phenotypic variation of D. bulgarica that can assist in developing management strategies. Our findings also highlight the vital need for quarantine measures and the production of healthy plant materials to prevent the introduction and spread of the pathogen in Iran.  相似文献   

20.
The production of sunflower is threatened by Orobanche cumana (broomrape) infections in many countries of southern and eastern Europe. The most virulent race of this parasitic weed, race F, is widespread in Spain. Most of the current commercial hybrids of resistant sunflower do not completely prevent broomrape emergence in the field. The performance (broomrape incidence and severity, final yields and oil contents) of four resistant and two susceptible sunflower hybrids was studied in different years in several O. cumana – infested locations. O. cumana – sunflower interactions were characterised by low severity and intermediate incidence in the resistant hybrids; both depended on the environment. An increase in sunflower yield because of the use of resistant hybrids was most noticeable under heavy field infestations and under drought. Characterisation of 20 populations of O. cumana classified as race F in terms of the standardised area under the degree of attack progress curve (SAUDC) and O. cumana incidence (BI) suggested differential intrinsic pathogenicities. These results highlight the variability within race F of O. cumana , mirroring the environmentally dependent horizontal resistance in sunflower.  相似文献   

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