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1.
There is an increasing interest in the legume species Medicago truncatula as a model plant for structural and functional genomic studies that can be used to identify agronomically important genes in legumes. Field screening has shown very high levels of resistance to Orobanche crenata in M. truncatula. However, in vitro studies with O. crenata, Orobanche foetida, Orobanche ramosa and Orobanche minor showed useful variation among accessions at early stages of the parasite–host interaction. Significant differences were observed in the levels of germination of O. crenata and O. foetida seeds induced by different accessions of M. truncatula. Only limited germination was observed on accession SA‐4327. All accessions induced little O. ramosa and O. minor germination. Accessions also varied in the number of O. crenata and O. foetida attachments supported, with few developing on accession SA‐27774. The variation observed for induction of germination and of subsequent attachment will be useful to isolating and characterizing genes involved in the early stages of Orobanche–host plant interaction and for the study of the biosynthetic pathways of production for germination stimulants.  相似文献   

2.
Various Orobanche species are weedy and cause severe reduction in the yields of many important crops. The seeds of these parasitic weeds may remain dormant in the soil for many years until germination is stimulated by the release of a chemical signal from a host plant. In order to determine the effects of fenugreek root exudate on the induction of Orobanche crenata, Orobanche ramosa and Orobanche foetida seed germination, root exudate was collected from hydroponically grown fenugreek seedlings. Fractionation patterns obtained from column and thin layer chromatography of the fenugreek root exudate showed a set of metabolites differing in their polarity with stimulatory activity on Orobanche seed germination. The crude root exudate stimulated both O. ramosa and O. crenata seed germination to the same level caused by the synthetic germination stimulant GR24 at 10 mg L?1. It also stimulated O. foetida seed germination which did not respond to GR24. Active fractions of root exudate stimulated the germination of Orobanche species differentially.  相似文献   

3.
BACKGROUND: Orobanche and Phelipanche species (the broomrapes) are root parasitic plants, some of which represent serious weed problems causing severe yield losses on important crops. Control strategies have largely focused on agronomic practices, resistant crop varieties and herbicides, albeit with marginal success. An alternative control method is the induction of suicidal seed germination with natural substances isolated from root exudates of host and non‐host plants. RESULTS: Soyasapogenol B [olean‐12‐ene‐3,22,24‐triol(3β,4β,22β)] and trans‐22‐dehydrocampesterol [(ergosta‐5,22‐dien‐3‐ol, (3β,22E,24S)] were isolated from Vicia sativa root exudates. They were identified by comparing their spectroscopic and optical properties with those reported in the literature. Soyasapogenol B was very specific, stimulating the germination of O. minor seeds only, whereas trans‐22‐dehydrocampesterol stimulated P. aegyptiaca, O. crenata, O. foetida and O. minor. CONCLUSION: Soyasapogenol B and trans‐22‐deydrocampesterol were isolated for the first time from Vicia sativa root exudates, and their biological activity as stimulants of Orobanche or Phelipanche sp. seed germination was reported. Copyright © 2011 Society of Chemical Industry  相似文献   

4.
The broad‐host‐range necrotizing fungal pathogen Rhizoctonia solani is responsible for economically significant diseases to crops as diverse as wheat, maize, barley, canola, sugar beet, potato, soyabean, bean, lupin and alfalfa. Germplasm screens in many of the crop hosts have not identified strong genetic resistance which, together with the lack of effective control, mean the pathogen remains a substantial problem for agriculture in many parts of the world. Following the establishment of a robust inoculation assay, a germplasm collection of the model legume Medicago truncatula was screened with various legume‐infecting isolates of R. solani. While some significant differences in susceptibility/resistance were detected between some lines, in the majority of cases M. truncatula was susceptible to R. solani. Comparison of a legume‐ and cereal‐infecting AG8 isolate with a legume‐specific AG11 isolate revealed no difference in pathogenicity between the two isolates when infecting M. truncatula. The most significant differences in susceptibility occurred with an AG6 isolate, which caused root canker. This included significant differences between the moderate resistance of the M. truncatula reference genotype A17 and the high susceptibility of line A20. The analysis of a recombinant inbred line population derived from A17 and A20 revealed a single locus contributing to the resistance in A17. Interestingly, the locus only affected the development of post‐emergent (late) symptoms, such as necrosis of cotyledons at 11 days after inoculation and root‐ and above‐ground‐weights, but not pre‐emergent seedling damping off. These findings pave the way for further studies to dissect the genetic and molecular mechanisms of resistance.  相似文献   

5.
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   

6.
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   

7.
Aphanomyces euteiches (races 1 and 2) causes root rot of alfalfa; however, its population biology and distribution are poorly understood where alfalfa is a major crop. The objectives of this study were to (1) characterise the distribution and frequency of races of A. euteiches in Illinois alfalfa fields, (2) determine host range of A. euteiches on cultivated and native legumes, and (iii) to describe genetic diversity and population genetic structure of A. euteiches in alfalfa fields. To accomplish this, soil samples (n = 103) were collected from 30 alfalfa fields in 18 Illinois counties. Using the susceptible cv. ‘Saranac’, 148 isolates of A. euteiches were baited from the soil. The virulence phenotype of isolates representing all 18 counties was tested, and 54% were R1 and 46% were R2. Both races were detected in 61% of the counties, whereas only R1 was detected in 22% and R2 in 17%. Thirteen legume hosts for isolates from alfalfa fields were identified based on symptoms and/or production of oospores in roots. In addition to six previously known hosts, seven species were susceptible to infection: kura clover, purple prairie clover, white prairie clover, ladino clover, hairy vetch, Canadian milk vetch, and Illinois tick trefoil. AFLP analysis revealed high levels of genetic diversity among the isolates from different fields and counties and a lack of genetic structuring of populations based on race or geographical origin. The results suggest that populations of A. euteiches in alfalfa fields are diverse, often composed of races 1 and 2, and create risk for alfalfa and to multiple cultivated and native legume species.  相似文献   

8.
Pathogenicity of Aphanomyces spp. from Different Leguminous Crops in Sweden   总被引：1，自引：0，他引：1  
Host range and pathogenicity of a range of Aphanomyces spp. isolates obtained from pea roots but also from a range of other field-grown leguminous crops in southern Sweden was investigated. The Aphanomyces euteiches isolates originating from pea and the few obtained isolates originating from alfalfa, green bean and yellow sweet-clover were highly pathogenic only to pea. The A. euteiches isolated from common vetch differed from these isolates by being weakly pathogenic to pea and other legumes, but highly pathogenic to common vetch. Vetch isolates also formed a well-defined separate cluster based on principal component analysis of pathogenicity pattern on tested crops. Oospores of A. euteiches were observed in root tissue of pea as well as common vetch, alfalfa, green bean, broad bean, red clover and yellow sweet-clover in the greenhouse pathogenicity tests. An Aphanomyces sp. that morphologically differed from A. euteiches, was frequently isolated from several leguminous plants, but was non-pathogenic to all tested crops in the pathogenicity tests. In isozyme analysis the banding pattern of these isolates resembled the pattern of A. cladogamus. Another, different and so far unidentified Aphanomyces sp. from roots of green bean and broad bean, was also non-pathogenic to the tested legume species. Based on the isolates tested, the results obtained suggest that the population of Aphanomyces spp. infecting legume roots in Sweden consists of a pea-specific and a vetch-specific group of A. euteiches. Two other groups comprised (i) Aphanomyces sp. isolates that resembled A. cladogamus, and (ii) isolates, which resembled neither A. euteiches nor A. cladogamus. In addition, the host range of Swedish A. euteiches isolates was not as broad as reported for A. euteiches isolates from other countries.  相似文献   

9.
Seeds of Orobanche aegyptica Pers., O. cernua Leofl. and O. crenata Forsk. were introduced into the rumen of three rumen-canulated rams. Infectious seeds of all Orobanche species were found in the faeces as indicated by infecting different host plants in pot experiments. There were indications that the seeds of O. crenata are the most susceptible to the detrimental effects of the animal's digestive processes on their infectivity, whereas the O. aegyptica Pers. seeds are the most resistant of the three species tested. The consequences of these findings in connection with the spread of the pest as a result of agricultural practices are discussed.  相似文献   

10.
Barley scald fungus, Rhynchosporium commune, belongs to a host‐specialized species complex infecting grasses. Coalescent analyses of several genes indicate that R. commune originated c. 2500 years ago, after the domestication of barley. Phylogeographical analyses identified a diversity hotspot in Scandinavia, indicating an origin in northern Europe. After its emergence, R. commune became distributed globally on infected seeds, eventually invading the Fertile Crescent and infecting wild barley progenitors. Analyses of gene flow identified historical routes of migration out of Scandinavia and indicate a high degree of modern gene flow among South Africa, Australia and New Zealand. About 76% of global species diversity is found within barley fields, with all field populations showing a genetic structure consistent with sexual recombination. High levels of regional gene flow suggest wind‐dispersed ascospores and movement of infected seed. Quantitative traits, including pathogen aggressiveness, thermal sensitivity and fungicide resistance, showed high heritability and high levels of diversity within nine globally representative populations. Field experiments provided evidence for a fitness cost associated with complex virulence and a trade‐off between pathogenic and saprophytic fitness. All findings indicate that global R. commune populations have significant potential to evolve rapidly in response to environmental changes, including deployment of resistant cultivars, fungicide applications and global warming. Specific recommendations to improve management of barley scald include: (i) focus resistance breeding efforts in northern Europe, which offers the best location to screen germplasm and may provide useful sources of scald resistance; (ii) improve seed treatment, certification and quarantine programmes to limit long distance pathogen movement; (iii) manage barley stubble to decrease pathogen population size, limit production of sexual inoculum and reduce the pathogen's evolutionary potential.  相似文献   

11.
The consequence of 10 successive monocultural cycles involving different legume species/cultivars on the inoculum potential (IP) of soils naturally infested by Aphanomyces euteiches was investigated under greenhouse conditions. The results showed that the IP of a soil naturally infested by A. euteiches can be significantly modified not only by the non‐host or host status of crop species but also by the level of resistance of the cultivar. Susceptible species/cultivars (pea, lentil and susceptible cultivars of vetch and faba bean) are very favourable to pathogen multiplication, and continuous cultivation of each of these increased the IP values of a soil with a moderate initial IP (from 1·9 to 3·5 after 10 cycles). Conversely, non‐host species and resistant cultivars of vetch or faba bean contributed to reducing the IP values of soils irrespective of the initial IP (from 1·9 to 0·5 and from 4 to 2, respectively, after 10 cycles). Aphanomyces root rot severity values on the resistant legume species/cultivars were not affected by the successive cultural cycles. This study, which showed that the IP of A. euteiches in soil can be reduced by planting appropriate legume species and cultivars in greenhouse conditions, will be useful for defining better crop successions for legumes.  相似文献   

12.
Aphanomyces root rot ( Aphanomyces euteiches ) has become a very destructive disease in French pea crops since 1993. The host specificity of the French pea-infecting populations of this pathogen was investigated by inoculating pea, common vetch, alfalfa, broad bean and green bean with 91 pea-infecting A. euteiches isolates, originating from the main areas of infestation in France. These isolates were compared to 13 isolates from various countries and hosts (pea, green bean, alfalfa). Virulence phenotypes were defined according to the pathogenicity data on the different hosts: all isolates from France infected two to five legume species, with most infecting pea, vetch, alfalfa and broad bean. Four pathotypes were characterized within the French isolates: one type corresponded to broad host range isolates, the second was composed of isolates preferentially agressive on pea/vetch/alfalfa and weakly aggressive on broad bean, and two others corresponding to more specialized isolates that preferentially infected pea/vetch or pea/vetch/alfalfa. Most isolates from France were preferentially pathogenic on pea, like the pea-infecting isolates from other countries, but were less specialized than the alfalfa- and green bean-infecting isolates from other countries. These results suggest that A. euteiches isolates may be maintained on wild or cultivated legumes other than pea in France.  相似文献   

13.
BACKGROUND: Orobanche spp. represent a serious threat to a wide range of crops. They are difficult targets for herbicides, and biological control could provide a possible solution. This work therefore aimed to formulate mycoherbicides of Fusarium with adequate shelf life and virulence against Orobanche but safe to faba bean and tomato. RESULTS: Only two isolates of Fusarium oxysporum Schlecht. (Foxy I and Foxy II) obtained from diseased Orobanche shoots were found to be pathogenic to Orobanche crenata Forsk. and Orobanche ramosa L. Conidial suspension of both isolates significantly decreased germination, attachments and tubercles of Orobanche. Microconidia and chlamydospores of both isolates were formulated as mycoherbicides encapsulated in a wheat flour–kaolin matrix (four different formulations). All formulations greatly diminished Orobanche emerged shoots, total shoot number, shoot height, attachment of emerged shoots, the germinated seeds that succeeded in emerging above the soil surface and dry weight. Meanwhile, disease incidence and disease severity of emerged shoots were enhanced. The shelf life was adequate, particularly for coarse, freshly prepared, low‐temperature‐stored, microconidia‐rich formulations. The induced growth reduction of Orobanche‐infected host plants seemed to be nullified by formulations, particularly at the highest dose. CONCLUSION: These formulations seemed to destroy Orobanche but appeared harmless to host plants. Hence, they could be efficiently used as mycoherbicides for biological control of Orobanche in faba bean and tomato. Copyright © 2008 Society of Chemical Industry  相似文献   

14.
Experiments were performed to elucidate the biochemical nature of the differential response of resistantVicia atropurpureacv. Popany and susceptibleVicia sativacv. Yovel to the parasitic weedOrobanche aegyptiaca. Plant root material was obtained by growing vetch plants in association withOrobancheseeds on glass microfibre filter sheets inserted in polyethylene bags replenished by nutrient solution. Higher concentrations of bound phenolics, free phenolics and lignin, and higher activity of peroxidase were observed in cv. Popany roots as a result ofO. aegyptiacainfection than were found in cv. Yovel vetch. No differences in hydroxyproline-rich glycoproteins levels were detected between infected and non-infected roots of either vetch cultivar. These results suggest that the resistant vetch defense mechanism involves elevated induction of the phenylproponoid pathway uponOrobancheinfection, conferring mechanical and chemical barriers confronting the invading parasite.  相似文献   

15.
The genetic diversity of the late blight pathogen Phytophthora infestans infecting cultivated potato and alternative hosts growing in the vicinity of fields in the main potato-growing areas of the Peruvian Andes was characterized using collections from 1997–2013 as reference. The Peruvian P. infestans population, including previously collected and current isolates, consists of four clonal lineages (EC-1, US-1, PE-3 and PE-7) that belong to the A1 mating type and have been present in the country for decades. The first report of US-1 was in isolates collected between 1982 and 1986; meanwhile, EC-1 and PE-3 appeared for the first time in isolates from 1992 and PE-7 was found in 1997. The pathogen has a very broad host range among the solanaceous plants infecting cultivated potato, tomato, pear melon and several wild species. The solanaceous species growing in the vicinity of the potato fields sampled were identified and surveyed for late blight-like symptoms. Phytophthora infestans was isolated from nine wild species, including three new host species: Solanum zahlbruckneri, Solanum grandidentatum and Iochroma grandiflorum. There was no clear host specialization, but geographical substructuring was found as well as changes in the pathogen populations at the regional level. The clonal lineage EC-1, which is mostly resistant to metalaxyl, has complex virulence and contains a high level of subclonal variation, continues to dominate the population. Some multilocus genotypes of the EC-1 lineage were sampled in high frequencies and were found among the previously collected and new samples.  相似文献   

16.
Limited information is available about the spatial distribution and evolution of Blumeria graminis f.sp. hordei populations in North African countries, such as Morocco. Frequencies of virulence alleles in B. graminis populations are mainly driven by selection exerted by host resistance genes in addition to neutral processes such as migration and genetic drift. In Morocco, in contrast to Europe, there has been no systematic deployment of resistant cultivars, although some R genes are present in the traditional varieties. This is expected to result in the evolution of pathotypes with virulence to different R genes, and higher diversity in Morocco compared to Europe. To test this, we used 24 differential cultivars to characterise 72 isolates from Morocco in 2009. We assessed diversity and spatial structure of pathotypes and compared them to past isolates from the same area (collected in 1992). There was a high diversity of pathotypes. Isolates from 2009 were distinct from isolates from 1992, due to loss of virulence to Mla12, increased virulence to Mla8, Mla3 and Mlk1, and decreased virulence to Mla6, Ml(Ru2), Mlg and MlLa. Many virulences were different from those observed in European and Asian populations of B. graminis. At the spatial scale investigated, airborne dispersal and a lack of strong selection in the host population likely prevented the formation of population structure and allowed the accumulation of high isolate diversity. The evolution of novel and distinct pathotypes since 1992 is likely attributable to gene flow from Europe and selection by the host population in Morocco.  相似文献   

17.
ABSTRACT Using molecular markers, this work compares the genetic diversity in Colletotrichum gloeosporioides infecting species of the tropical forage legume Stylosanthes at the center of origin in Brazil and Colombia with that of Australia, China, and India, where Stylosanthes spp. have been introduced for commercial use. There was extensive diversity in the pathogen population from Brazil, Colombia, China, and India. The Australian pathogen population was least diverse probably due to its geographical isolation and effective quarantine. The extensive diversity in China and India means that threats from exotic pathogen races to Stylosanthes pastures can potentially come from countries outside the South American center of origin. In Brazil and India, both with native Stylosanthes populations, a high level of genetic differentiation in the pathogen population was associated with sites where native or naturalized host population was widely distributed. There was limited genetic diversity at germplasm evaluation sites, with a large proportion of isolates having identical haplotypes. This contrasts recent pathogenicity results for 78 of the Brazilian isolates that show hot spots of complex races are more common around research stations where host germplasm are tested, but few are found at sites containing wild host populations. For a pathogen in which the same races arise convergently from different genetic backgrounds, this study highlights the importance of using both virulence and selectively neutral markers to understand pathogen population structure.  相似文献   

18.
A method was developed by which the presence of broomrape (Orobanche spp.) seeds in vetch seeds was determined quantitatively. The broomrape seeds are washed out of the vetch seeds by a combination of two sieves. The vetch seeds remain on the top sieve and the broomrape seeds are collected on the lower sieve with square openings of 100 μm, which do not permit passage of the broomrape seeds. An appropriate statistical method for estimating the true mean number of broomrape seeds per sample in a large vetch seeds lot is presented and discussed. Détermination quantitative des graines d' orobanche dans des graines de vesce. Une méthode permettant de dénombrer la présence de graines d'orobanche dans un lot de graines de vesce a été mise au point. Les graines d'orobanche sont séparées de celles de vesce par une succession de deux tamis. Les graines de vesce sont maintenues sur le tamis supérieur et les graines d'orobanche sont collectées sur le tamis le plus bas avec une maille de 100 μm qui ne permet pas le passage des graines d'orobanche. Une méthode statistique appropriée pour estimer la quantité réelle d'orobanches dans un grand lot de semences de vesce est présentée puis discutée. Quantitative Bestimmung von Orobanche-Samen in Wicken-Saatgut Es wurde eine Methode entwickelt, mit der Orobanche-Samen in Wicken-Saatgut quantitativ erfasst werden können. Zum Trennen der Samen wurden 2 Siebe verwendet, wobei die Wicken-Samen im oberen, die Orobanche-Samen im unteren mit einer Maschenweite von 100 μm gesammelt wurden. Eine statistische Methode für die Schätzung der Orobanche-Samenmenge in grossen Wicken-Saatgutpartien wurde vorgestellt und diskutiert.  相似文献   

19.
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   

20.
Tree tomato, Solanum betaceum, is an Andean fruit crop previously shown to be attacked by Phytophthora andina in Ecuador and Colombia. Blight‐like symptoms were discovered on tree tomato plants in the central highlands of Peru in 2003 and shown to be caused by P. andina. Isolates of P. andina, collected from three different plantations in Peru over a 6‐year time span (2003–2008), were compared genetically with P. andina isolates from Colombia and Ecuador to test whether the pathogen population is geographically structured in the Andes. Restriction fragment length polymorphism (RFLP), mitochondrial DNA and simple sequence repeat (SSR) genetic markers, and mating type behaviour indicated that the Peruvian P. andina population from tree tomato is genetically distinct from populations infecting tree tomato in Colombia (CO‐1) and Ecuador (EC‐3, Ia, A1), but is more similar to the population infecting solanaceous hosts of the Anarrhichomenum complex (EC‐2, Ic, A2). Such geographic substructuring within this pathogen species could result from spatial isolation. Most strikingly, in contrast to the Ecuadorian and Colombian P. andina isolates from tree tomato, the Peruvian isolates have the A2 mating type. The presence of both mating types in the Andean population of P. andina attacking tree tomato indicates a risk of sexual reproduction and the presence of long‐lasting oospores in this pathosystem.  相似文献   

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