Search

[ES] Phytophthora es uno de los géneros fitopatógenos más relevantes y agresivos en la agricultura y silvicultura. Muestreos realizados en la última década han revelado una gran cantidad de interacciones entre especies de Phytophthora y plantas, desconocidas con anterioridad. La introducción de nuevos patógenos de suelo, como Phytophthora en los bosques de Fagaceae, modifica la comunidad microbiana presente en la rizosfera, con importantes consecuencias ambientales y económicas. El género Quercus es uno de los géneros de Fagaceae más extendidos en Europa, y Quercus ilex es la especie dominante en España. El vínculo entre la dispersión de Phytophthora en los ecosistemas naturales y las actividades del ser humano, ha sido previamente estudiado. Numerosos muestreos en viveros y espacios públicos, mostraron la presencia de gran diversidad de especies de Phytophthora que podían suponer una amenaza para la producción y los ecosistemas naturales. En este contexto, se realizó un muestreo de viveros ornamentales y forestales en cuatro comunidades autónomas españolas, centrándose en los posibles síntomas asociados a Phytophthora en diferentes hospedantes e incluyendo muestras de agua de los viveros. Los resultados mostraron 17 filotipos de Phytophthora que afectan a 22 especies vegetales incluidas en 19 géneros. Algunas de estas interacciones se citaron por primera vez en España. Entre los patógenos de suelo aislados en los viveros, se identificó una gran cantidad de formas asexuales tipo Cylindrocarpon en las raíces de hospedantes leñosos. Se caracterizó una colección de aislados mediante estudios morfológicos y moleculares. Se identificaron 12 especies pertenecientes a los géneros Cylindrodendrum, Dactylonectria e Ilyonectria en hospedantes pertenecientes a 15 géneros y otras cuatro nuevas especies se describieron. El estudio demostró la prevalencia de este grupo fúngico asociado con plántulas de diversos hospedantes que muestran síntomas de decaimiento en viveros forestales. Se evaluó la susceptibilidad de Q. ilex a la inoculación con ocho especies de Phytophthora obtenidas de muestreos en viveros. Las especies más agresivas fueron Phytophthora cinnamomi, Phytophthora cryptogea, Phytophthora gonapodyides, Phytophthora plurivora y Phytophthora psychrophila, seguidas de Phytophthora megasperma, mientras que Phytophthora quercina y Phytophthora nicotianae fueron las especies menos agresivas. Los resultados obtenidos en el ensayo de patogenicidad confirmaron que todas las especies de Phytophthora evaluadas podrían representar una amenaza para los encinares. En este contexto, se realizó un estudio para verificar la presencia y / o detección de especies de Phytophthora en dos áreas de España (dehesas del sudoeste y bosque del noreste) utilizando diferentes métodos de aislamiento y detección. El aislamiento directo y el método de trampeo vegetal en muestras obtenidas a partir de encinas con y sin decaimiento, identificaron Phytophthora cambivora, P. cinnamomi, P. gonapodyides, P. megasperma y Phytophthora pseudocryptogea en las dehesas, mientras que, en el bosque del noreste, no se aisló Phytophthora spp. Los análisis estadísticos indicaron que no había una relación significativa entre la frecuencia de aislamiento de las especies de Phytophthora y la expresión de los síntomas de la enfermedad en las encinas de las dehesas. Además, P. quercina se detectó con mayor frecuencia que P. cinnamomi en las dos áreas estudiadas utilizando sondas TaqMan de PCR a tiempo real. Se evaluaron seis masas de Q. ilex ubicadas en tres comunidades autónomas de España mediante “Next Generation Sequencing” (NGS) para tener un mayor conocimiento sobre la diversidad de Phytophthora spp. en los bosques de encinas. Se detectaron 37 filotipos de Phytophthora pertenecientes a los clados 1 al 12, excepto los clados 4, 5 y 11, lo que demuestra una gran diversidad de Phytophthora en los encinares estudiados. Los filotipos más abundantes fueron P. quercina, P. psychrophila, P. cinnamomi y P. plurivora., [EN] Phytophthora is one of the most relevant and aggressive plant pathogenic genus in agriculture and forestry. Due to the increasing environmental threat of invasive plant pathogens, monitoring new areas in the last decade has revealed a large number of new Phytophthora species-plant host interactions. The introduction of soilborne pathogens, such as Phytophthora in Fagaceae forests modifies the microbial community present in the rhizosphere with relevant environmental and economic consequences. The genus Quercus is one of the most extended Fagaceae genera in Europe, and Q. ilex is the dominant tree in Spain. The link between Phytophthora dispersion in natural ecosystems and human derived activities has been previously studied. Numerous sampling in nurseries and public spaces revealed a great diversity of Phytophthora species that compromised production and threated natural ecosystems. In this context, sampling ornamental and forest nurseries in four Spanish regions was carried out focusing on possible symptoms associated to Phytophthora on different hosts and including water samples from the nurseries. The results showed 17 Phytophthora phylotypes affecting 22 plant species included in 19 plant genera and some of them reported for the first time in Spain. Among the soilborne pathogens isolated in the nurseries, a large number of Cylindrocarpon-like asexual morphs were identified from the roots of woody hosts. A collection of Cylindrocarpon-like isolates recovered from Spanish nurseries was characterised by morphological and molecular studies. Twelve species belonging to the genera Cylindrodendrum, Dactylonectria and Ilyonectria were identified from damaged roots of 15 different host genera and other four species were newly described. The study demonstrated the prevalence of this fungal group associated with seedlings of diverse hosts showing decline symptoms in forest nurseries in Spain. The susceptibility of Quercus ilex to the inoculation with eight Phytophthora species obtained from nurseries was evaluated. The most aggressive species were Phytophthora cinnamomi, Phytophthora cryptogea, Phytophthora gonapodyides, Phytophthora plurivora and Phytophthora psychrophila followed by Phytophthora megasperma, while Phytophthora quercina and Phytophthora nicotianae were the least aggressive species. Results obtained in the pathogenicity test confirmed that all Phytophthora species tested could represent a threat to holm oak ecosystems. In this context, a study to verify the presence and/or detection of Phytophthora species was conducted in two holm oak areas of Spain (southwestern dehesas and northeastern woodland) using different isolation and detection methods. Direct isolation and baiting methods in declining and non-declining holm oak trees revealed Phytophthora cambivora, P. cinnamomi, P. gonapodyides, P. megasperma, and Phytophthora pseudocryptogea in the dehesas, while in the northeastern woodland, no Phytophthora spp. were recovered. Statistical analyses indicated that there was not a significant relationship between the Phytophthora spp. isolation frequency and the disease expression of the holm oak stands in the dehesas. Phytophthora quercina and P. cinnamomi TaqMan real-time PCR probes showed that P. quercina was detected in a higher frequency than P. cinnamomi in both studied areas. A better understanding of the Phytophthora spp. diversity in holm oak forests was assessed using Next Generation Sequencing (NGS) in six Q. ilex stands located in three regions in Spain. Thirty-seven Phytophthora phylotypes belonging to clades 1 to 12, except for clades 4, 5 and 11, were detected in this study, demonstrating a high diversity of Phytophthora species in holm oak Spanish forests. The most abundant phylotypes were P. quercina, P. psychrophila, P. cinnamomi and P. plurivora. In summary, this Thesis demonstrated a high diversity of Phytophthora and Cylindrocarpon-like species in Spanish nurseries, reporting new pathogen-plant host in, [CA] Phytophthora és un dels gèneres fitopatògens més rellevants i agressius en l'agricultura i la silvicultura. Mostrejos realitzats en l'última dècada han revelat una gran quantitat d'interaccions desconegudes fins ara entre espècies de Phytophthora i plantes. La introducció de nous patògens del sòl, com Phytophthora en els boscos de Fagaceae, modifica la comunitat microbiana present en la rizosfera, amb importants conseqüències ambientals i econòmiques. El gènere Quercus és un dels gèneres de Fagaceae més estesos a Europa, i Quercus ilex és l'espècie dominant a Espanya. El vincle entre la dispersió de Phytophthora en els ecosistemes naturals i les activitats de l'ésser humà, ja ha sigut estudiat prèviament. Nombrosos mostrejos en vivers i espais públics, van mostrar la presència d'una gran diversitat d'espècies de Phytophthora que podien suposar una amenaça per a la producció i els ecosistemes naturals. En aquest context, es va realitzar un mostreig de vivers ornamentals i forestals en quatre comunitats autònomes espanyoles, centrant-se en els possibles símptomes associats a Phytophthora en diferents hostes i incloent mostres d'aigua dels vivers. Els resultats van mostrar 17 filotipus de Phytophthora que afecten 22 espècies vegetals incloses en 19 gèneres. Algunes d'aquestes 'interaccions es van citar per primera vegada a Espanya. Entre els patògens del sòl aïllats en els vivers, es va identificar una gran quantitat de formes asexuals tipus Cylindrocarpon en les arrels de plantes llenyoses. Es va caracteritzar una col·lecció d'aïllats mitjançant estudis morfològics i moleculars. Es van identificar 12 espècies pertanyents als gèneres Cylindrodendrum, Dactylonectria i Ilyonectria en hostes pertanyents a 15 gèneres i altres quatre noves espècies es van descriure. L'estudi va demostrar la prevalença d'aquest grup fúngic associat amb plàntules de diversos hostes que mostren símptomes de decaïment en vivers forestals espanyols. Es va avaluar la susceptibilitat de Q. ilex a la inoculació amb huit espècies de Phytophthora obtingudes de mostrejos en vivers. Les espècies més agressives van ser Phytophthora cinnamomi, Phytophthora cryptogea, Phytophthora gonapodyides, Phytophthora plurivora i Phytophthora psychrophila, seguides de Phytophthora megasperma, mentre que Phytophthora quercina i Phytophthora nicotianae van ser les espècies menys agressives. Els resultats obtinguts en l'assaig de patogenicitat van confirmar que totes les espècies de Phytophthora avaluades podrien representar una amenaça per als ecosistemes d'alzines. En aquest context, es va realitzar un estudi per a verificar la presència i / o detecció d'espècies de Phytophthora en dues àrees d'Espanya (deveses del sud-oest i bosc del nord-est) utilitzant diferents mètodes d'aïllament i detecció. L'aïllament directe i el mètode de parany vegetal en mostres obtingudes a partir d'alzines, amb i sense decaïment, van identificar Phytophthora cambivora, P. cinnamomi, P. gonapodyides, P. megasperma i Phytophthora pseudocryptogea en les deveses, mentre que, en el bosc del nord-est, no es va aïllar Phytophthora spp. Les anàlisis estadístiques van indicar que no hi havia una relació significativa entre la freqüència d'aïllament de les espècies de Phytophthora i l'expressió dels símptomes de la malaltia en les alzines en les deveses. A més, P. quercina es va detectar amb major freqüència que P. cinnamomi en les dues àrees estudiades utilitzant sondes TaqMan de PCR a temps real. Es van avaluar sis masses de Q. ilex situades en tres comunitats autònomes d'Espanya mitjançant "Next Generation Sequencing" (NGS) per a tindre un major coneixement sobre la diversitat de Phytophthora spp. en els boscos d'alzines. Es van detectar 37 filotipus de Phytophthora pertanyents als clades 1 al 12, excepte els clades 4, 5 i 11, la qual cosa demostra una gran diversitat d'espècies de Phytophthora en els alzinars estudiats. Els filotipus més abundants van ser P. quercina, P. psychrophila, P. cinnamomi i P. plurivora.

The antifungal activity of the entomopathogenic fungi isolates Metarhizium brunneum EAMb 09/01-Su and Beauveria bassiana EABb 09/16-Su against the olive pathogens Verticillium dahliae and Phytophthora megasperma was evaluated. The crude extract and its partial purified fractions obtained from both isolates showed complete inhibition of the mycelial growth of V. dahliae. However, the same fractions obtained from B. bassiana EABb 09/16-Su were less effective against the mycelial growth of P. megasperma. Our results showed that M. brunneum EAMb 09/01-Su had the highest fungicidal activity, inhibiting the mycelial growth of both pathogens. Both fractions IV and VI from M. brunneum EAMb 09/01-Su were evaluated by the progress of the Verticillium wilt of the plant and showed clear antagonism against V. dahliae, reducing the severity of the symptoms between 38.9 and 58.9%. The active metabolite obtained from M. brunneum not only reduced the germination of V. dahliae microsclerotia but also inhibited hyphal formation, decreased the number of reproductive structures, and changed the conformation of the microsclerotial colony, preventing the formation of new microsclerotia. The evaluation of temperature, UV light and pH on the antifungal activity of the dialyzed fraction from M. brunneum showed that the antifungal activity was stable at 60 °C (2 h) and 120 °C (20 min) and to UV light radiation. However, the exposition to the dialyzed fraction at pH 7.5 and 8.5 affected the antifungal activity. The results of this study clearly showed that the entomopathogenic fungus M. brunneum EAMb 09/01-Su produces antifungal compounds that reduce the number of the pathogen propagules in the soil and the severity of Verticillium wilt. Therefore, this resource should be further studied as an alternative for the integrated management of Verticillium wilt and Phytophthora root rot, which is the most severe disease in all traditional olive-growing regions worldwide, and as a reliable and sustainable strategy for a reduced reliance on pesticides.

Hypocotyl inoculations of differential soybean (Glycine max) cultivars were used to identify seven new physiologic races of Phytophthora sojae (syn. P. megasperma f. sp. glycinea). Five of the new races were virulent on soybeans with the Rps1-d allele, while four of the new races were virulent on soybeans with the Rps1-k allele. The Rps1-k and Rps1-d alleles provide resistance to a majority of the previously described races that cause Phytophthora root and stem rot. The seven new races were assigned race numbers 33, 34, 41, 42, 43, 44, and 45 since race numbers 35 through 40 were assigned to other new races recently identified in Ohio, California, Arkansas, and Iowa. The new races identified in this study constituted 14% of the 1993 isolates evaluated from 27 counties in central and northern Indiana. Races 1 and 3 were the most prevalent, representing 31 and 26% of the P. sojae isolates identified in 1993. Races 4, 6, 7, 8, 9, 13, 28, and 29 each constituted 2 to 6% of the 1993 isolates. Other races identified among the 1993 isolates included races 19, 21, 25, and 30.

Several species of the genus Phytophthora are associated with root rot and trunk cankers in olive trees (Olea europaea L.). Among them, Phytophthora megasperma has been cited as being associated with olive root rots in Greece (1). Unidentified species of Pythium and Phytophthora have also been associated with olive tree root rots in the United States. However, the status of P. megasperma and Pythium spp. as olive tree root pathogens has remained unclear. Following a 5-year period of severe drought in southern Spain, autumn-winter rainfall rates in 1996 to 1997 steadily increased in both quantity and frequency. Under these unusually wet conditions, olive trees remained waterlogged for several months. During this period, we observed foliar wilting, dieback, and death of young trees, and later found extensive root necrosis. In 46 of 49 affected plantations surveyed, P. megasperma was consistently isolated from the rotted rootlets, particularly in young ( Reference: (1) H. Kouyeas and A. Chitzanidis. Ann. Inst. Phytopathol. Benaki 8:175, 1968.

A lupine baiting technique was used to detect the presence of Phytophthora spp. in several streams, irrigation reservoirs, and drainage canals used in cranberry cultivation. P. cinnamomi was found to be widely distributed throughout the study area in the southern New Jersey Pinelands, and was present both upstream and downstream of agricultural activities. A second species, identified as P. megasperma, was more restricted in its distribution and was never isolated from a water system that did not also contain P. cinnamomi. In a survey of commercial cranberry production, 80% of the acreage represented (approximately 37% of total New Jersey production area) was exposed to one or both Phytophthora spp. through application of infested water from irrigation reservoirs. Based on the widespread distribution of P. cinnamomi, it is likely that this pathogen was introduced many years prior to its discovery on cranberry in the 1980s, which corresponded to the adoption of overhead irrigation in the crop. There were slight differences between the two species in seasonal occurrence. The highest levels of P. cinnamomi were found during the summer months (July to August) whereas P. megasperma was highest during the spring (April to May) and fall (September to October) months.

In August 2002, Phytophthora megasperma Drechs. was isolated from wilted plants of Asparagus officinalis L. cv. Guelph Millenium displaying spear and crown rot. Six affected plants were sampled in a commercial asparagus field located in the Saguenay-Lac-Saint-Jean Region (300 km northeast of Montreal, Quebec, Canada). The fungus was isolated from asparagus fern stalks, crown tissue, and spears after a rainy period and identified using morphological and cultural characteristics (2). In pinkish 4-week-old cultures, unbranched stalks bore abundant sporangia, which were ovoid to obpyriform in shape, 15 to 45 m long, and 10 to 30 m in diameter. Characteristic circular oospores >30 m in diameter were produced on V8 juice agar at 25°C in darkness after 1 month. Pathogenicity was tested on asparagus cvs. Guelph Millenium and Jersey Knight. A mycelium suspension (3 ml at 106 CFU/ml) prepared from 1-week-old shaken potato dextrose (PD) broth was sprayed on 30 1-week-old seedlings grown in petri plates filled with sterilized, moist, sandy soil and held at 20°C (day/night). Controls received sterile PD broth. Within 3 weeks of incubation in the dark, inoculated seedlings exhibited necrotic symptoms similar to those observed initially, while controls remained healthy. The pathogen was isolated from 75% of the ‘Guelph Millenium’ and 98% of the ‘Jersey Knight’ symptomatic seedlings, but not isolated from the control seedlings. In North America, disease caused by P. megasperma resulting in yield loss has been reported in California and New York (1,3). In Canada, the etiology of asparagus diseases is not well characterized. To our knowledge, this is the first report of P. megasperma on asparagus plants in Canada. References: (1) P. A. Ark and J. T. Barrett. Phytopathology 28:754, 1938. (2) D. C. Erwin et al. Phytophthora: Its Biology, Taxonomy, Ecology, and Pathology. The American Phytopathological Society, St Paul, MN, 1983. (3) T-L. Kuan and D. C. Erwin. Phytopathology 70:333, 1980.

Since 2009, a severe decline leading to mortality has been observed affecting nearly 5 ha of a wild olive woodland of high ecological value in Seville, southern Spain. Phytophthora cryptogea and P. megasperma were consistently isolated from roots and rhizosphere of trees with symptoms sampled in 2009, 2011 and 2013. The isolates were identified on the basis of colony and reproductive structure morphology as well as temperature–growth relationships, and identification was further corroborated by their ITS and β-tubulin sequences. Koch's postulates were demonstrated for both species on 1-year-old wild olives. Pathogenicity tests showed that both Phytophthora spp. are highly aggressive pathogens, although temperature–growth requirements for each species were distinct. As a consequence, the two species may be active in different seasons and their epidemiology may be differently influenced by global climate change, and they may show their active periods in different climatic scenarios. The climate change models for the Mediterranean Basin forecast a global temperature increase that favours the more thermophilic P. cryptogea. The high susceptibility to phytophthora root rot should not be disregarded in olive breeding programmes where wild olive is used as a source of resistance to verticillium wilt. This article is protected by copyright. All rights reserved.

Phenotypic and sequence data were used to characterize 28 isolates resembling Phytophthora megasperma from 14 host species in 2 plant production facilities and 10 restoration sites across the San Francisco Bay Area (California; USA). Size of the oogonia and DNA sequences (nuclear internal transcribed spacer (ITS) and mitochondrial cytochrome c oxidase subunit 1 (COX 1)) were compared, and sensitivity to mefenoxam and pathogenicity were measured. Based on ITS 61 % of isolates matched ex-type sequences of Phytophthora crassamura from Italy, and the remainder matched or were close to the P. megasperma ex-type. However, all California P. crassamura genotypes belonged to four unique COX 1 haplotype lineages isolated from both nurseries and restoration sites. Although lineages were sensitive to mefenoxam, a significant difference in sensitivity was identified, and all continued growth in-vitro. These results suggested previous mefenoxam exposure in plant production facilities resulting in tolerance. In conclusion, all evidence pointed to a nursery origin of novel P. crassamura lineages found in California restoration sites. In this study, COX 1 sequences and oogonia size provided information relevant to identify geographic and evolutionary intraspecific variation within P. crassamura, and was additionally used to track the spread of this species from nurseries into wildlands.

The struggling Spanish holm oak woodland situation associated with Phytophthora root rot has been studied for a long time. Phytophthora cinnamomi is considered the main, but not the only species responsible for the decline scenario. This study verifies the presence and/or detection of Phytophthora species in two holm oak areas of Spain (southwestern &ldquo, dehesas&rdquo, and northeastern woodland) using different isolation and detection approaches. Direct isolation and baiting methods in declining and non-declining holm oak trees revealed Phytophthora cambivora, Phytophthora cinnamomi, Phytophthora gonapodyides, Phytophthora megasperma, and Phytophthora pseudocryptogea in the dehesas, while in the northeastern woodland, no Phytophthora spp. were recovered. Statistical analyses indicated that there was not a significant relationship between the Phytophthora spp. isolation frequency and the disease expression of the holm oak stands in the dehesas. Phytophthora quercina and P. cinnamomi TaqMan real-time PCR probes showed that both P. cinnamomi and P. quercina are involved in the holm oak decline in Spain, but P. quercina was detected in a higher frequency than P. cinnamomi in both studied areas. Thus, this study demonstrates that molecular approaches complement direct isolation techniques in natural and seminatural ecosystem surveys to determine the presence and distribution of Phytophthora spp. This is the first report of P. pseudocryptogea in Europe and its role in the holm oak decline should be further studied.

Cocoa black pod caused by Phytophthora is one of the most serious diseases affecting cocoa production. This project set out was to improve our knowledge of the molecular mechanisms involved in Theobroma cacao resistance. We performed a transcriptional screening using macroarrays containing 89 ESTs from subtractive libraries enriched with genes differentially expressed in response to T. cacao/Phytophthora interactions. A gene expression analysis revealed the induction of genes involved in stress signal transduction, general and specific defence genes and genes involved in hormone signalling pathways. RT-qPCR showed that the level expression of two genes in the resistant plant was higher during the first eight hours after pathogen inoculation. Three genes from a family encoding a protease inhibitor displayed different levels of expression depending on resistant and susceptible T. cacao clones. A comparison of promoter sequences revealed a motif present only in genes that were up-expressed in the resistant plant.

New diseases of Easter lily and lettuce were noticed in Japan and the pathogens were identified initially as Phytophthora megasperma and Phytophthora sp., respectively, based on morphological characteristics. We re-examined these isolates using phylogenetical and morphological analysis. In a detailed phylogenetic analysis of all clade members that was based on the sequences of eight genomic regions, Easter lily isolates formed a monophyletic group with high bootstrap support. The unique colony pattern supported this result. In separate analyses of Phytophthora clade 8 based on rRNA gene ITS and the cox 1 gene sequences, the lettuce isolates grouped with P. lactucae (described from lettuce in Greece) in the rRNA gene ITS tree but formed a distinct group in the cox 1 tree. The sporangia of Japanese lettuce isolates germinated directly, an uncommon feature in clade 8b. These results suggested that the Easter lily and lettuce isolates are novel species that we formally describe as Phytophthora lilii sp. nov. and P. pseudolactucae sp. nov., respectively. Moreover, P. lilii appears to represent a new Phytophthora clade.

To investigate the role that ginsenosides (and some of their metabolites) play in interactions between plants and phytopathogenic fungi (e.g. Cylindrocarpon destructans (Zinss) Scholten), we systematically determined the anti-fungal activities of six major ginsenosides (Rb1, Rb2, Rc, Rd, Re and Rg1), along with the metabolites of ginsenoside Rb1 (Gypenoside XVII (G-XVII) and F2), against the ginseng root pathogen C. destructans (Zinss) Scholten and non-ginseng pathogens Fusarium graminearum Schw., Exserohilum turcicum (Pass.) Leonard et Suggs, Phytophthora megasperma Drech. and Pyricularia oryzae Cav. Our results showed that the growth of both ginseng pathogens and non-pathogens could be inhibited by using the proto-panaxatriol (PPT) ginsenosides Re and Rg1. In addition, the growth of the non-pathogens could also be inhibited by using proto-panaxadiol (PPD) ginsenosides Rb1, Rb2, Rc and Rd, whereas the growth of ginseng pathogen C. destructans (Zinss) Scholten was enhanced by ginsenosides Rb1 and Rb2. In contrast, ginsenoside G-XVII and F2 strongly inhibited the hyphal growth of both C. destructans (Zinss) Scholten and the non-pathogens tested. Furthermore, addition of sucrose to the media increased the growth of C. destructans (Zinss) Scholten, whereas glucose did not affect the growth. Moreover, C. destructans (Zinss) Scholten and all four non-pathogens were able to deglycosylate PPD ginsenosides using a similar transformation pathway, albeit with different sensitivities. We also discussed the anti-fungal structure-activity relationships of the ginsenosides. Our results suggest that the pathogenicity of C. destructans (Zinss) Scholten against ginseng root is independent of its ability to deglycosylate ginsenosides.

A Hypocrea/Trichoderma strain was isolated from cacao (Theobroma cacao L.) pods from a cacao plantation in Huimanguillo, Tabasco, Mexico. The strain was identified as H./T. viridescens ITV43 by its morphological characteristics and DNA sequence analysis of ITS1-5.8s-ITS2 and was tested against Moniliophthora roreri Cif & Par and Phytophthora strains by confrontation experiments. The biocontrol of H./T. viridescens ITV43 measured as biocontrol index (BCI) at seven days against M. roreri(HT-ITV01, HT-ITV20, HT-ITV27), P. megasperma (HT-ITV08, HT-ITV15, HT-ITV37) and P. capsici (HT-ITV14, HT-ITV16, HT-ITV33) strains ranged from 78.28-81.63, 63.04-69.95 and 69.77-76.31%, respectively. After 31 days of incubation, the BCI values increased to 81.52-86.50 for M. roreri and 100% for Phythopthora strains. Samples taken from the interaction zone were observed by optical and scanning electron microscopy. The results show the effect of H./T. viridescens ITV43 strain on morphological deformations and disorganization of the M. roreri and Phytophthora cell wall structures. Highest BCI values obtained suggest that the Hypocrea strains isolated from T. cocoa could have the ability to antagonize more efficiently against fungal pathogens of this crop. Key words: Antagonism, Hypocrea, mycoparasitism, Moniliophthora, Phytophthora, Theobroma.

A new disease of rose was noticed in Chiba Prefecture of Japan in 1968, and the pathogen was initially identified as Phytophthora megasperma based on morphological characteristics. Similar Phytophthora isolates have since been collected from rose plants in Chiba, Kanagawa, and Shizuoka Prefectures. In 2005, several Phytophthora isolates were recovered from crowns of strawberry plants in Hokkaido Prefecture. These were considered to be members of a new species. In this study, we re-examined all these isolates using morphological and physiological studies and a multilocus phylogenetic analysis. The rose and strawberry isolates were mostly similar morphologically and physiologically, with some exceptions. The rose isolates differed significantly from P. megasperma sensu stricto and other related Phytophthora species. The rose and strawberry isolates had external proliferation of sporangia, characteristic funnel-shaped oogonia, predominantly paragynous antheridia, and fast growth rates of 10.5 mm/24 h at an optimum temperature of 28 °C. In the multilocus phylogenetic tree constructed using sequences from the rDNA ITS regions, rDNA LSU, and the translation elongation factor 1-α, β-tubulin and coxI genes, they formed a distinct monophyletic group in clade 7 with strong bootstrap support. The rose and strawberry isolates separated into two distinct groups. The results indicate that the rose and strawberry isolates constitute two separate species, designated here as Phytophthoranagaii and P. fragariaefolia.

Bacillus cereus UW85 was isolated from a root of a field-grown alfalfa plant from Arlington, WI, and identified for its ability to suppress damping off, a disease caused by Phytophthora megasperma f. sp. medicaginis on alfalfa. Here, we report the draft genome sequence of B. cereus UW85, obtained by a combination of Sanger and Illumina sequencing.

El cacao venezolano, reconocido a nivel mundial por sus excelentes cualidades aromáticas procedentes del cacao tipo criollo, es considerado también el más sensible a plagas y enfermedades. una de las enfermedades que afectan a las plantaciones de cacao en la zona Sur del Lago de Maracaibo, es la “Mancha de agua”, causada por Phytophthora megasperma dreschler, que ocasiona sobre los frutos una mancha de color marrón claro, de bordes regulares concéntricos que puede llegar a cubrir toda la mazorca, y afectar a las semillas. en este trabajo, 68 árboles de cacao de las colecciones vivas del inia y de coRpozulia, fueron caracterizados mediante 23 marcadores microsatélite y evaluados en su respuesta ante P. megasperma. De estos árboles, fueron desprendidas mazorcas en madurez fisiológica, inoculadas mediante aspersión de gotas finas, con 1x105 zoosporas/ml y mantenidas por cuatro días a 26ºc, en cámara húmeda y oscuridad. se evaluó el nivel de resistencia de cada individuo, según una escala cualitativa, en un rango del 1 (altamente resistente) al 8 (altamente susceptible), considerando presencia, tamaño y características de las lesiones observadas. la prueba para datos no paramétricos de Kruskal y Wallis reveló variabilidad en los niveles de resistencia a P. megasperma, confirmando su naturaleza poligénica, en las plantas evaluadas. el análisis del adn reveló genotipos, desde criollos homocigotas, hasta Forasteros homocigotas. la respuesta de resistencia fue variable en cultivares heterocigotas, mostrando 10 árboles alta resistencia e igualmente fue variable en criollos homocigotas, mostrando dos de ellos alta resistencia al patógeno. The venezuelan cocoa recognized worldwide for its excellent aromatic qualities, is derived from the criollo cultivars, which also happen to be highly susceptible to pests and diseases. among the diseases that affect the Criollo cocoa plantations of the South of the Maracaibo Lake, is the “Mancha de Agua” caused by Phytophthora megasperma dreschler. this pathogen develops on the fruits light brown concentric lesions with defined borders, which it may penetrate in the inner tissues damaging the cocoa seeds. The present research involved 68 trees, belonging to the collections of inia and coRpozulia; these were characterized using 23 microsatellite markers and tested for resistance to P. megasperma. physiologically mature pods from the selected trees were detached and inoculated by spraying fine drops containing 1x105zoospores/ml and kept four days at 26ºc, in a humid chamber in complete darkness. the level of resistance was evaluated in each individual according to a qualitative scale, which ranged from 1 (highly resistant) to 8 (highly susceptible), considering presence, size and characteristics of the lesions. all of the results were analyzed by the Kruskal-Wallis test for Non Parametric data. Our results revealed an important variability, confirming the polygenic nature of the resistance to P.megasperma in evaluated plants. the dna analysis revealed a broad range of diversity; ranging from homozygous criollo, to homozygous Forastero genotypes. Resistance levels were highly variable in the heterocigote cultivars, of which 10 cultivars resulted highly resistant; whereas in the criollo homozygous trees, only two of them proved to be resistant. 144 - 163 marseg@ula.ve Anual

In vitro dose responses of several calcium and potassium salts were determined on some commercially significant plant pathogens, including: Helminthosporium solani, Fusarium oxysporum f. sp. pisi race 2, Colletotricum coccodes, Phytophthora cactorum, Phytophthora cinnamomi, Phytophthora erythroseptica, Phytophthora infestans, Phytophthora megasperma, Pythium ultimum, and Venturia inaequalis. Mycelial growth inhibition was both salt-specific and dose-related. Pythium ultimum was completely inhibited by 75 mg·L−1 or greater calcium propionate, but needed 300 mg·L−1 or greater of calcium acetate and 40 mL·L−1 or greater of potassium silicate for complete inhibition. Phytophthora infestans was completely inhibited by 150 mg·L−1 or greater calcium acetate, 150 mg·L−1 or greater calcium propionate, or 5 mL·L−1 or greater potassium silicate. Phytophthora cactorum was completely inhibited by 300 mg·L−1 or greater calcium propionate, but required 600 mg·L−1 or greater calcium acetate and 10 mL·L−1 or greater potassium silicate for complete inhibition. Phytophthora cinnamomi was completely inhibited by calcium propionate at 600 mg·L−1 or greater or by 10 mL·L−1 or greater potassium silicate. Only potassium silicate inhibited Phytophthora megasperma, Phytophthora erthroseptica, V. inequalis, and H. solani at concentrations of 5 mL·L−1 or greater, 20 mL·L−1 or greater, 40 mL·L−1 or greater, or 80 mL·L−1 or greater, respectively. Potassium acetate did not completely inhibit any of the pathogens in this study when tested at concentrations 1200 mg·L−1 or less.

The impact of environmental factors and microbial and chemical control methods on cacao pod production dynamics and spread of black pod disease caused by Phytophthora megakarya was assessed over three consecutive years in a smallholder’s plantation. Significant positive correlations were found between rainfall records and pod rot incidence when assessed after a 1-week lag. Disease distribution across various pod developmental stages showed that immature pods were the most susceptible to P. megakarya attack. Weekly observations of the pod distribution and disease progression at various developmental stages on cacao trees sprayed with fungicide Ridomil, Trichoderma asperellum biocontrol agent (strain PR11), or untreated control trees indicated that the total pod production and the incidence of black pod rot was significantly different between the treatments. The disease rates were 1.73%, 47.1% and 71.23% in the plots treated with fungicide, PR11 and untreated, respectively, in 2004, and 0.67%, 11.35% and 34.04% in the same plots in 2005. A significant carry over effect of the biological agent was noticed up to 1 year after the sprays with strain PR11 were halted. The disease incidence averaged 16.67% in the plots previously sprayed with PR11 and 35.88% in the control plot, although both the plots were sprayed with the same contact fungicide, Kocide. Monitoring through enumeration and molecular typing revealed that Trichoderma propagules remained consistently more abundant in flower cushions of cacao trees than in soil or bark. This study showed that microbial control of black pod disease with PR11 was promising but not as effective as the chemical methods under the current high disease pressure, and therefore needs to be integrated with other control methods to establish a sustainable management system for black pod disease in Cameroon.

As part of a participatory selection programme, promising individual trees were selected in 2004 in cocoa farms of southern and western Cameroon regions for yield and for low incidence of Phytophthora pod rot (Ppr) caused by Phytophthora megakarya. The aim of this study was to compare the levels of resistance to Ppr between farm accessions (FA), introduced and local genebank accessions (GA). In total, 234 FA were grafted in the nursery together with 22 introduced GA and 73 local GA, and tested for resistance to P. megakarya by leaf disc inoculations. The introduced GA, that were reported as resistant to Ppr in other countries, proved to be more resistant than the selected FA and unselected FA and also more resistant than the 3 control clones for Ppr resistance used in the study. However, approximately 10% of the FA were as resistant as the average of the introduced GA, showing the potential of selection for resistance to Ppr in farmers’ fields. The average level of resistance of the FA was relatively higher than that of the local GA. The FA selected for yield and low Ppr incidence in the field were more resistant in the leaf disc test than the unselected FA. The use of FA and of farmers’ knowledge in the participatory selection process is valuable in obtaining Ppr-resistant cultivars.

Three forage Brassica species were evaluated for their growth and adaptability to the Rocky Mountain region. Brassicas were grown in fields infested with a Phytophthora disease previoıısly observed on kale (Brassica oleracea var. Acephala) Metalaxyl treatmıent did not affect Brassica yields signifıcantly. Although pest problems were detected, Brassica crops tolerated low temperatures and produced excellent yields ( up to 9.90 Mg/ha). The Phytophthora isolates from Brassica, which were identifed as Phytophthora megasperma, differed from the alfalfa (Medicago sativa) pathogen Phytophthora megasperma f.sp. medicaginis which appeared to be host specifıc., Yem bitkisi olarak kullanılan üç Brassica türü Kayalık Dağlar bölgesinde (ABD) yetişmeleri, şartlara ve çevreye uyma yetenekleri yönünden incelenmiştir. Brassica türleri önceden Brassica oleracea var. acephala ‘kale’ üzerinde gözlemlenen bir Phytophthora hastalığı ile enfekteli tarlalarda yetiştirilmiştir. Metalaxyl muamelesinin Brassica mahsul miktarını önemli bir ölçüde etkilemediği görülmüştür. Zararlı problemlerinin olmasına rağmen Brassica türleri düşük ısı derecelerine tolerans göstermişler ve 9.90 Mg/ha a kadar ürün alınmıştır. Brassica türlerinden izole edilen Phytophthora izolatları Phytophthora megasperma olarak teşhis edilmiştir. Bu izolatlar konukçuya özelleşmiş olarak gözüken yonca izolatı Phytophthora megasperma f.sp. medicaginis izolatından farklılıklar göstermiştir.

Black pod rot, caused by Stramenopiles of the genus Phytophthora, leads to serious production losses in all cocoa growing zones. In order to reduce the impact of these pests, preference is given to genetic control using resistant varieties, and sources of resistance are actively being sought, particularly in wild cacao trees. Surveys were undertaken in the natural cacao tree populations of south-eastern French Guiana between 1985 and 1995 and an abundant amount of plant material belonging to a particular genetic group, the "Guiana" group, was collected. A great deal of work has shown the merits of this genetic group as a source of resistance to Phytophthora palmivora and megakarya. We describe here the results of a global study to assess the resistance of the 186 clones in the "Guiana" group "core collection" to a Guianese strain of Phytophthora capsici (strain Reg 2-6). This study, which used an efficient methodology (fifteen series of tests on leaf discs and a statistical test adapted to the ordinal nature of the basic data), showed that the "Guiana" genetic group is a major source of resistance to P. capsici. Strain Reg 2-6 proves to be particularly virulent, as the Scavina 6 control, an international reference for resistance to Phytophthora, is not resistant to it. However, 24 clones of the "Guiana" group are, and 92 have proved to be more resistant than Scavina 6, thereby showing the interest of the group in genetically controlling P. capsici. Thus, of the clones in the Guiana group that are more resistant to P. capsici than Scavina 6, some, which are also resistant to P. palmivora and/or Phytophthora megakarya, and also displaying some other notable qualities, could be incorporated into cocoa genetic improvement programmes in countries where P. capsici is rife on cacao trees. (Resume d'auteur)

The phenolic composition of olive roots and stems was studied by high performance liquid chromatography–mass spectrometry. The in vivo levels of the principal phenolic compounds found in olive plants infected by Phytophthora megasperma Drechsler and Cylindrocarpon destructans (Zinssm.) Scholten differed from the levels observed in non-infected plants. When the antifungal activity of these compounds against both fungi was studied in vitro , the most active were quercetin and luteolin aglycons, followed by rutin, oleuropein, p -coumaric acid, luteolin-7-glucoside, tyrosol and catechin. Microscopic study showed that these phenolic compounds affected the growth, morphology and ultrastructure of the fungi. Taken together, these findings suggest that the phenolic compounds present in olive plants play an active role in the protection against pathogen attack.

Summary Phytophthora cryptogea, Phytophthora cinnamomi, Phytophthora cambivora, Phytophthora megasperma and Pythium undulatum were isolated from diseased Noble fir (Abies procera) seedlings and soil associated with dead Noble fir in Ireland. Seedlings of four Christmas tree species (A. procera, Picea sitchensis, Picea abies and Pinus contorta) were inoculated with these oomycetes to test their pathogenicity and the susceptibility of the various tree species. Phytophthora spp. and Pythium undulatum caused root rot on all tree species. Disease symptoms included reddish brown cambial discoloration, crown symptoms, brown foliage, dark brown roots, root rot and seedling mortality. These symptoms were similar to those observed on Noble fir in naturally infested plantations. Pythium undulatum appeared as the most virulent pathogen followed by P. cinnamomi, P. cambivora, P. megasperma and P. cryptogea. Noble fir showed to be most susceptible and lodgepole pine most tolerant while Sitka spruce and Norway spruce were intermediate. Resume Phytophthora cryptogea, P. cinnamomi, P. cambivora, P. megasperma et Pythiumundulatum ont ete isoles de semis de sapins malades (Abies procera) et de sol associea des sapins morts en Irlande. Des semis de quatre especes de sapins de Noel (A. procera, Picea sitchensis, P. abies et Pinus contorta) ont ete inocules avec ces oomycetes pour tester leur pouvoir pathogene et la sensibilite des differentes especes d'arbres. Phytophthora spp. et Pythium undulatum ont cause des necroses racinaires chez toutes les especes. Les symptomes comprennent une coloration rouge-brune du cambium, des symptomes aeriens, une coloration brune du feuillage, un brunissement des racines, une pourriture racinaire et la mortalite des semis. Ces symptomes sont identiques a ceux observes dans les plantations d‘Abies procera naturellement infectees. Pythium undulatum est apparu comme le pathogene le plus virulent suivi par Phytophthora cinnamomi, P. cambivora, P. megasperma et P. cryptogea.A. procera est l'espece la plus sensible, Pinus contorta la plus tolerante, tandis que les especes d’epiceas (Picea sitchensis, P. abies) sont intermediaires. Zusammenfassung In Irland wurden Phytophthora cryptogea, P. cinnamomi, P. cambivora, P. megasperma und Pythium undulatum von kranken Edeltannensamlingen (Abies procera) und aus dem sie umgebenden Boden isoliert. Samlinge von vier Baumarten (A. procera, Picea sitchensis, P. abies und Pinus contorta), die zum spateren Verkauf als Christbaume angebaut werden, wurden mit diesen zu den Oomyceten gehorenden Pilzen beimpft, um deren Pathogenitat und die Anfalligkeit dieser Wirte zu testen. Alle Phytophthora und Pythium undulatum verursachten Wurzelfaulen auf allen Baumarten. Rot-braune Verfarbungen des Kambiums, Kronenverlichtungen, Nadelverbraunungen, dunkelbraune Verfarbungen der Wurzeln, Wurzelfaulen und das Absterben von Samlingen waren die haufigsten Krankheitssymptome. Die Symptome waren sehr ahnlich wie diejenigen an Edeltannen in Plantagen nach naturlichem Befall. Am virulentesten war Pythium undulatum gefolgt von Phytophthora cinnamomi, P. cambivora, P. megasperma und P.cryptogea. Die Edeltanne war am anfalligsten, die Drehkiefer (Pinus contorta) am resistentesten.

Vine decline of kiwifruit was observed in an orchard in Bartin province of Turkey. Affected vines exhibited poor terminal growth, leaf discoloration and various degrees of dieback, including complete vine death. Symptoms were observed in the field on roots, crowns and stems. Two Phytophthora species were isolated from decayed cortical roots and lower stems of kiwifruits. They were identified as Phytophthora cryptogea and Phytophthora megasperma by their morphological characteristics and the analysis of sequences of the internal transcribed spacer (ITS) region of the rDNA. Pathogenicity of the isolates was tested by stem inoculation on kiwifruit seedlings. After 4 weeks, cankers developed in the plants inoculated with P. cryptogea, while no cankers formed in those inoculated with P. megasperma and in control plants. This is the first report of P. cryptogea causing root and stem rot of kiwifruit in Turkey.

This is the first report of antifungal activity of Iranian Actinomycetes isolates against Alternaria solani Sorauer, Alternaria alternata (Fr.) Keissler, Fusarium solani (Mart.) Sacc., Phytophthora megasperma Drechsler, Verticillium dahliae Klebahn and Saccharomyces cerevisiae Meyen ex Hansen. Biological control of plant diseases has received worldwide attention in recent years mainly as a response to public concern about the use of hazardous chemicals in the environment. Soil Actinomycetes particularly Streptomyces spp. enhance soil fertility and have antagonistic activity against wide range of soil-borne plant pathogens. In search for soil Actinomycetes having antifungal activity against plant fungal-pathogens, 110 isolates were screened from which 14 isolates were found active at least against one of the tested fungi. Streptomyces plicatus strain101, Frankia sp. strain 103 and Streptomyces sp. strain 44 had the widest antifungal spectra of activity. Antifungal genes from these strains may be proper candidates for genetic engineering of plants for increased tolerance against the tested cosmopolitan fungal pathogens.

Phytophthora isolates associated with Phytophthora major ITS Clade 6 were grouped into 11 phenotypic taxa. These comprised the described morphospecies P. gonapodyides, P. megasperma s. str. and P. humicola; four previously identified but so far undescribed taxa, informally designated here P. sp. O-group, P. sp. Apple-cherry, P. taxon Pgchlamydo, and P. taxon Walnut; and four previously unknown taxa, designated P. taxon Oaksoil, P. taxon Raspberry, P. taxon Forestsoil, and P. taxon Riversoil. With the exception of P. gonapodyides, each phenotypic taxon represented an unique ITS lineage. Two isolates morphologically identical to P. gonapodyides comprised a separate lineage and probably represent another taxon, designated here P. taxon Salixsoil, P. humicola, P. sp. O-group, P. sp. Apple-cherry and P. taxon Walnut grouped together as subclade I. Within subclade II, P. taxon Oaksoil, P. taxon Raspberry, P. taxon Forestsoil, P. taxon Riversoil and P. taxon Pgchlamydo formed a cluster of closely related but phenotypically distinct lineages basal to P. gonapodyides and P. megasperma, P. taxon Salixsoil being the most basal member. The taxonomy, adaptation and breeding systems of Clade 6 taxa are discussed. They show a strong association with forests and riparian ecosystems, only a limited association with agriculture and an ability to tolerate high temperatures. Also, in contrast to most other Phytophthora clades, Clade 6 taxa are predominantly sterile or inbreeding in culture. Only one taxon, P. sp. O-group, appears classically A1/A2 heterothallic.

Ca2+ and calmodulin (CaM), a key Ca2+ sensor in all eukaryotes, have been implicated in defense responses in plants. To elucidate the role of Ca2+ and CaM in defense signaling, we used 35S-labeled CaM to screen expression libraries prepared from tissues that were either treated with an elicitor derived from Phytophthora megasperma or infected with Pseudomonas syringae pv. tabaci. Nineteen cDNAs that encode the same protein, pathogen-induced CaM-binding protein (PICBP), were isolated. The PICBP fusion proteins bound 35S-CaM, horseradish peroxidase-labeled CaM and CaM-Sepharose in the presence of Ca2+ whereas EGTA, a Ca2+ chelator, abolished binding, confirming that PICBP binds CaM in a Ca2+-dependent manner. Using a series of bacterially expressed truncated versions of PICBP, four CaM-binding domains, with a potential CaM-binding consensus sequence of WSNLKKVILLKRFVKSL, were identified. The deduced PICBP protein sequence is rich in leucine residues and contains three classes of repeats. The PICBP gene is differentially expressed in tissues with the highest expression in stem. The expression of PICBP in Arabidopsis was induced in response to avirulent Pseudomonas syringae pv. tomato carrying avrRpm1. Furthermore, PICBP is constitutively expressed in the Arabidopsisaccelerated cell death2-2 mutant. The expression of PICBP in bean leaves was also induced after inoculation with avirulent and non-pathogenic bacterial strains. In addition, the hrp1 mutant of Pseudomonas syringae pv. tabaci and inducers of plant defense such as salicylic acid, hydrogen peroxide and a fungal elicitor induced PICBP expression in bean. Our data suggest a role for PICBP in Ca2+-mediated defense signaling and cell-death. Furthermore, PICBP is the first identified CBP in eukaryotes with four Ca2+-dependent CaM-binding domains.

We have compared localized (LAR) and systemic (SAR) acquired resistance induced in tobacco by a hypersensitive response (HR) inducing Phytophthora megasperma glycoprotein elicitin. Three different zones were taken into account: LAR, SART and SARS. The LAR zone was 5–10 mm wide and surrounded the HR lesion. SART was the tissue of the elicitor-treated leaf immediately beyond the LAR zone. The systemic leaf was called SARS. Glycoprotein-treated plants showed enhanced resistance to challenge infection by tobacco mosaic virus (TMV). Disease resistance was similar in SART and SARS, and higher in LAR. The expression pattern, in glycoprotein-treated plants, of acidic and basic PR1, PR2, PR3 and PR5 proteins and of O-methyltransferases (OMT), enzymes of the phenylpropanoid pathway, was similar to that in TMV-infected plants. OMT was stimulated in LAR but not in SART and SARS. The four classes of acidic and basic PR proteins accumulated strongly in LAR. Reduced amounts of acidic PR1, PR2, PR3 and only minute amounts of basic PR2 and PR3 accumulated in SART and SARS. In glycoprotein-treated plants, expression of the acidic and basic PR proteins in LAR and SAR of transgenic NahG and ETR tobacco plants and in LAR of plants treated with inhibitors of salicylic acid accumulation and of ethylene biosynthesis indicated a salicylic acid-dependent signalling pathway for acidic isoform activation and an ethylene-dependent signalling pathway for basic isoform activation.

Soybean (Glycine max) cv. Harosoy 63 is resistant to race 1 and susceptible to race 9 of Phytophthora megasperma f. sp. glycinea (Pmg). In detached primary leaves inoculated with zoospores, growth of race 1 was completely suppressed 16 h after inoculation, while race 9 was unaffected. The amount of the phytoalexin glyceollin that accumulated, however, was not significantly different in either the incompatible or compatible interaction 16 h after inoculation. At the circumference of the inoculated area, a slight accumulation of phytoalexin was observed only in the incompatible interaction 20 h or more after inoculation. Tolerance of race 9 to the phytoalexin was significantly higher than that of race 1 when the phytoalexin was added to agar. Moreover, race 9 degraded glyceollin faster than race 1. On leaves inoculated at separate points with either race, the lesion associated with race 9 never colonized areas inoculated with race 1. These results suggest that factor(s) other than the accumulation of phytoalexin in soybean tissue might cause cessation of growth of Pmg.