A survey in natural forest ecosystems of Vietnam reveals high diversity of both new and described Phytophthora taxa including P. ramorum

In 2016 and 2017, surveys of Phytophthora diversity were performed in 25 natural and semi-natural forest stands and 16 rivers in temperate and subtropical montane and tropical lowland regions of Vietnam. Using baiting assays from soil samples and rivers and direct isolations from naturally fallen leaves, 13 described species, five informally designated taxa and 21 previously unknown taxa of Phytophthora were isolated from 58 of the 91 soil samples (63.7%) taken from the rhizosphere of 52 of the 64 woody plant species sampled (81.3%) in 20 forest stands (83.7%), and from all rivers: P. capensis, P. citricola VII, VIII, IX, X and XI, P. sp. botryosa-like 2, P. sp. meadii-like 1 and 2, P. sp. tropicalis-like 2 and P. sp. multivesiculata-like 1 from Phytophthora major phylogenetic Clade 2; P. castaneae and P. heveae from Clade 5; P. chlamydospora, P. gregata, P. sp. bitahaiensis-like and P. sp. sylvatica-like 1, 2 and 3 from Clade 6; P. cinnamomi (Pc), P. parvispora, P. attenuata, P. sp. attenuata-like 1, 2 and 3 and P. ×heterohybrida from Clade 7; P. drechsleri, P. pseudocryptogea, P. ramorum (Pr) and P. sp. kelmania from Clade 8, P. macrochlamydospora, P. sp. ×insolita-like, P. sp. ×kunnunara-like, P. sp. ×virginiana-like s.l. and three new taxa, P. sp. quininea-like, P. sp. ×Grenada 3-like and P. sp. ×Peru 4-like, from Clade 9; and P. sp. gallica-like 1 and 2 from Clade 10. The A1 and A2 mating types of both Pc and Pr co-occurred. The A2 mating type of Pc was associated with severe dieback of montane forests in northern Vietnam. Most other Phytophthora species, including Pr, were not associated with obvious disease symptoms. It is concluded that (1) Vietnam is within the center of origin of most Phytophthora taxa found including Pc and Pr, and (2) Phytophthora clades 2, 5, 6, 7, 8, 9, and 10 are native to Indochina.info:eu-repo/semantics/publishedVersio

Influencia de "Phytophthora cinnamomi" Rands en el decaimento de "Quercus ilex L." y su relación con las propiedades del suelo y las ectomicorrizas

El decaimiento de la encina (“Quercus ilex” L.) afecta a todo el Mediterráneo, y entre los factores implicados, se han descrito la degradación del suelo, el estrés hídrico y los cambios en la humedad edáfica y en la abundancia de micorrizas. El principal factor biótico es el oomiceto “Phytophthora cinnamomi” Rands. El presente trabajo analiza la influencia de “P. cinnamomi” en el decaimiento de la encina y, cómo las propiedades físico-químicas del suelo, las ectomicorrizas y la humedad edáfica afectan la infección de las encinas por “P. cinnamomi”. Se realizaron tres tipos de estudios en el sudoeste peninsular: (i) uno en 96 focos, donde se seleccionaron tres encinas con decaimiento y tres asintomáticas y se analizaron la presencia de “P. cinnamomi” y “Pythium spiculum”, la abundancia de ectomicorrizas, varias propiedades del suelo y la densidad radical; (ii) otro contemplando un seguimiento temporal de la humedad edáfica, el nivel freático, la presencia de “P. cinnamomi”, la abundancia de ectomicorrizas y varios parámetros fisiológicos, y (iii) otro en invernadero. Los resultados mostraron que la pudrición de raíces causada por “P. cinnamomi” en combinación con factores que influyen en su actividad (una menor densidad del suelo, una textura fina y espesores gruesos del horizonte Ah, propiedades relacionadas con los valores de humedad) afectan el vigor de la encina. Las alteraciones en la abundancia y diversidad de ectomicorrizas también se relacionan con el decaimiento de la encina. Asimismo, una sequía prolongada afecta a la encina y aumenta su posterior susceptibilidad a “P. cinnamomi”.Holm oak (“Quercus ilex” L.) decline is extended in the Mediterranean region and among the factors involved, soil degradation, water stress, changes in soil moisture and shifts in mycorrhizal symbiosis have been described. The main biotic factor associated with holm oak decline is the oomycete “Phytophthora cinnamomi” Rands. The present work aims to assess the influence of “P. cinnamomi” on holm oak decline, and how soil properties, ectomycorrhizae, soil water content and water table affect “P. cinnamomi” infections of holm oak. The work comprises three types of assessments in southwestern Spain: (i) an extensive including 96 declining stands, where three declining and three non-declining trees were selected and sampled for analyzing “P. cinnamomi” and “Pythium speculum” presence, abundance of ectomycorrhizae, physical and chemical soil properties and fine root density; (ii) a temporal assessment of soil water content, soil water table, “P. cinnamomi” presence, ectomycorrhizal fungi abundance and the physiological status of trees in 5 stands, and (iii) one performed under greenhouse conditions including 140 seedlings submitted to different watering regimes and subsequently inoculated with “P. cinnamomi”. Results showed that root rot caused by “P. cinnamomi” infection in combination with factors which favour the pathogen activity (lower soil bulk densities, fine textured soils and a thicker Ah horizon, properties which influence soil moisture values) play an important role in the vigour of holm oak. Disturbances in ectomycorrhizal abundance and diversity also related to holm oak decline. Long drought events also affected Q. ilex performance and increased subsequent susceptibility to “P. cinnamomi”.- Junta de Extremadura y Universidad de Extremadura. Convenio “Prospecciones de focos de “seca de Quercus”. - Junta de Extremadura (proyectos regionales III-PRI 08-A78 y IV-PRI IB10088) - Realizado dentro del marco de la acción COST “Established and emerging Phytophthora: increasing threats to woodland and forest ecosystems in Europe” (FP0801)

Influencia de "Phytophthora cinnamomi" Rands en el decaimento de "Quercus ilex L." y su relación con las propiedades del suelo y las ectomicorrizas

El decaimiento de la encina (“Quercus ilex” L.) afecta a todo el Mediterráneo, y entre los factores implicados, se han descrito la degradación del suelo, el estrés hídrico y los cambios en la humedad edáfica y en la abundancia de micorrizas. El principal factor biótico es el oomiceto “Phytophthora cinnamomi” Rands. El presente trabajo analiza la influencia de “P. cinnamomi” en el decaimiento de la encina y, cómo las propiedades físico-químicas del suelo, las ectomicorrizas y la humedad edáfica afectan la infección de las encinas por “P. cinnamomi”. Se realizaron tres tipos de estudios en el sudoeste peninsular: (i) uno en 96 focos, donde se seleccionaron tres encinas con decaimiento y tres asintomáticas y se analizaron la presencia de “P. cinnamomi” y “Pythium spiculum”, la abundancia de ectomicorrizas, varias propiedades del suelo y la densidad radical; (ii) otro contemplando un seguimiento temporal de la humedad edáfica, el nivel freático, la presencia de “P. cinnamomi”, la abundancia de ectomicorrizas y varios parámetros fisiológicos, y (iii) otro en invernadero. Los resultados mostraron que la pudrición de raíces causada por “P. cinnamomi” en combinación con factores que influyen en su actividad (una menor densidad del suelo, una textura fina y espesores gruesos del horizonte Ah, propiedades relacionadas con los valores de humedad) afectan el vigor de la encina. Las alteraciones en la abundancia y diversidad de ectomicorrizas también se relacionan con el decaimiento de la encina. Asimismo, una sequía prolongada afecta a la encina y aumenta su posterior susceptibilidad a “P. cinnamomi”.Holm oak (“Quercus ilex” L.) decline is extended in the Mediterranean region and among the factors involved, soil degradation, water stress, changes in soil moisture and shifts in mycorrhizal symbiosis have been described. The main biotic factor associated with holm oak decline is the oomycete “Phytophthora cinnamomi” Rands. The present work aims to assess the influence of “P. cinnamomi” on holm oak decline, and how soil properties, ectomycorrhizae, soil water content and water table affect “P. cinnamomi” infections of holm oak. The work comprises three types of assessments in southwestern Spain: (i) an extensive including 96 declining stands, where three declining and three non-declining trees were selected and sampled for analyzing “P. cinnamomi” and “Pythium speculum” presence, abundance of ectomycorrhizae, physical and chemical soil properties and fine root density; (ii) a temporal assessment of soil water content, soil water table, “P. cinnamomi” presence, ectomycorrhizal fungi abundance and the physiological status of trees in 5 stands, and (iii) one performed under greenhouse conditions including 140 seedlings submitted to different watering regimes and subsequently inoculated with “P. cinnamomi”. Results showed that root rot caused by “P. cinnamomi” infection in combination with factors which favour the pathogen activity (lower soil bulk densities, fine textured soils and a thicker Ah horizon, properties which influence soil moisture values) play an important role in the vigour of holm oak. Disturbances in ectomycorrhizal abundance and diversity also related to holm oak decline. Long drought events also affected Q. ilex performance and increased subsequent susceptibility to “P. cinnamomi”.- Junta de Extremadura y Universidad de Extremadura. Convenio “Prospecciones de focos de “seca de Quercus”. - Junta de Extremadura (proyectos regionales III-PRI 08-A78 y IV-PRI IB10088) - Realizado dentro del marco de la acción COST “Established and emerging Phytophthora: increasing threats to woodland and forest ecosystems in Europe” (FP0801)

Transgenerational Induction of Resistance to Phytophthora cinnamomi in Holm Oak

The maternal environment of a tree species can influence the development and resistance of its offspring. Transgenerational induction of resistance is well known in plants but its occurrence in forest tree species has been less reported. Quercus ilex L. (holm oak) is a widespread Mediterranean tree species threatened by the invasive Phytophthora cinnamomi Rands pathogen. The influence of P. cinnamomi on the offspring of infected Q. ilex mother trees has not been studied. This study compared the performance and tolerance to P. cinnamomi of seedlings from non-infected and P. cinnamomi-infected trees. Acorns from Q. ilex trees were collected from five forests. After isolations were conducted in the rhizosphere of several trees, in each forest, three trees were selected as non-infected and three were selected as P. cinnamomi-infected. Forty acorns per tree were weighed and sown under greenhouse conditions, and when plants were aged ~9 months they were challenged with P. cinnamomi. Plant mortality was higher in the offspring of non-infected trees than in the offspring of P. cinnamomi-infected trees (26.2% vs. 21.1%, respectively). Consistently, survival probabilities of seedlings from P. cinnamomi-infected trees were higher than those of seedlings from non-infected trees, particularly in seedlings with reduced growth. Although acorns from healthy Q. ilex trees were heavier than acorns from P. cinnamomi-infected trees, the time to death of inoculated seedlings was not influenced by seed weight. The time to death of seedlings was positively related to belowground mass, particularly to an increased proportion of fine secondary roots. We report transgenerational-induced resistance to P. cinnamomi in Q. ilex triggered by an unknown mechanism independent of acorn mass. Information about the persistence of transgenerational effects in Q. ilex offspring and the influence of these effects on plant fitness is crucial to improve the management and regeneration of this declining species

Transgenerational Induction of Resistance to <i>Phytophthora cinnamomi</i> in Holm Oak

The maternal environment of a tree species can influence the development and resistance of its offspring. Transgenerational induction of resistance is well known in plants but its occurrence in forest tree species has been less reported. Quercus ilex L. (holm oak) is a widespread Mediterranean tree species threatened by the invasive Phytophthora cinnamomi Rands pathogen. The influence of P. cinnamomi on the offspring of infected Q. ilex mother trees has not been studied. This study compared the performance and tolerance to P. cinnamomi of seedlings from non-infected and P. cinnamomi-infected trees. Acorns from Q. ilex trees were collected from five forests. After isolations were conducted in the rhizosphere of several trees, in each forest, three trees were selected as non-infected and three were selected as P. cinnamomi-infected. Forty acorns per tree were weighed and sown under greenhouse conditions, and when plants were aged ~9 months they were challenged with P. cinnamomi. Plant mortality was higher in the offspring of non-infected trees than in the offspring of P. cinnamomi-infected trees (26.2% vs. 21.1%, respectively). Consistently, survival probabilities of seedlings from P. cinnamomi-infected trees were higher than those of seedlings from non-infected trees, particularly in seedlings with reduced growth. Although acorns from healthy Q. ilex trees were heavier than acorns from P. cinnamomi-infected trees, the time to death of inoculated seedlings was not influenced by seed weight. The time to death of seedlings was positively related to belowground mass, particularly to an increased proportion of fine secondary roots. We report transgenerational-induced resistance to P. cinnamomi in Q. ilex triggered by an unknown mechanism independent of acorn mass. Information about the persistence of transgenerational effects in Q. ilex offspring and the influence of these effects on plant fitness is crucial to improve the management and regeneration of this declining species

Sjukdom på ålegras påvist flere steder langs norskekysten

Over hele verden har sjøgrasenger minsket dramatisk og blant de berørte artene er ålegras (Zostera spp.). Ålegrasenger er av stor betydning som oppvekststed for mange marine arter, blant dem torskeyngel. Ålegrasenger skades av mudring og andre fysiske inngrep i strandsoner, men ålegras er også utsatt for sjukdomsorganismer og andre biotiske skadegjørere. Vi rapporterer her funn av flere potensielt sjukdomsfremkallende arter av Phytophthora og Halophytophthora på ålegras langs norskekysten. Hvor mye disse artene bidrar til tilbakegangen av ålegras er usikkert, så videre forskning er nødvendig.publishedVersio

Sjukdom på ålegras påvist flere steder langs norskekysten

Over hele verden har sjøgrasenger minsket dramatisk og blant de berørte artene er ålegras (Zostera spp.). Ålegrasenger er av stor betydning som oppvekststed for mange marine arter, blant dem torskeyngel. Ålegrasenger skades av mudring og andre fysiske inngrep i strandsoner, men ålegras er også utsatt for sjukdomsorganismer og andre biotiske skadegjørere. Vi rapporterer her funn av flere potensielt sjukdomsfremkallende arter av Phytophthora og Halophytophthora på ålegras langs norskekysten. Hvor mye disse artene bidrar til tilbakegangen av ålegras er usikkert, så videre forskning er nødvendig

Isolation and Pathogenicity of Phytophthora Species from Poplar Plantations in Serbia

During a survey in three declining and three healthy poplar plantations in Serbia, six different Phytophthora species were obtained. Phytophthora plurivora was the most common, followed by P. pini, P. polonica, P. lacustris, P. cactorum, and P. gonapodyides. Pathogenicity of all isolated species to four-month and one-year-old cuttings of Populus hybrid clones I-214 and P&aacute;nnonia, respectively, was tested using both a soil infestation and stem inoculation test. Isolates of P. polonica, P. &times; cambivora, P. cryptogea, and P. &times; serendipita from other host plants were included as a comparison. In the soil infestation test, the most aggressive species to clone I-214 were P. plurivora, P. &times; serendipita, and P. pini. On clone P&aacute;nnonia, P. gonapodyides and P. pini were the most aggressive, both causing 100% mortality, followed by P. cactorum, P. &times; cambivora, and P. polonica. In the underbark inoculation test, the susceptibility of both poplar clones to the different Phytophthora species was largely similar, as in the soil infestation test, with the exception of P. polonica, which proved to be only weakly pathogenic to poplar bark. The most aggressive species to clone I-214 was P. pini, while on clone P&aacute;nnonia, the longest lesions and highest disease incidence were caused by P. gonapodyides. Phytophthora cactorum and P. plurivora were pathogenic to both clones, whereas P. &times; cambivora showed only weak pathogenicity. The implications of these findings and possible pathways of dispersion of the pathogens are discussed