Effect of grafting on phenology, susceptibility to Phytophthora cinnamomi and hormone profile of chestnut

Ink disease caused by the root-rot pathogen P. cinnamomi (Pc) threatens European sweet chestnut (Castanea sativa Mill.) orchards, and growers increasingly graft susceptible C. sativa traditional varieties on Pc-resistant hybrid commercial rootstocks. The influence of the scion, the rootstock, and grafting per se on the vegetative budburst, growth, susceptibility to Pc and defence-related hormone profile of Castanea spp. are unknown. In a greenhouse experiment, these effects were evaluated by reciprocally grafting two Pc resistant C. crenata x C. sativa clones and two Pc susceptible C. sativa clones. Resistance to Pc and the hormone content of leaves and roots were rootstock-dependent, and survival rates of susceptible chestnuts strongly increased when grafted on resistant rootstocks. The scion had no effect on the resistance to Pc and the hormone profile of leaves and roots of grafted trees, but influenced vegetative budburst and primary growth. Grafting per se increased susceptibility to Pc and altered the defence-related phytohormone content of trees, especially in resistant rootstocks, but did not influence budburst and growth of trees. Grafting-induced alteration of the constitutive defense-related hormone profile could explain the increased susceptibility of resistant rootstocks to Pc. Nine days after infection, a dynamic hormonal response consisting of decreased jasmonates (JA and JA-Ile) in leaves and increased ABA and JA-Ile in roots was observed in resistant chestnuts. This is the first study addressing the role of grafting in modulating resistance to the soil-borne pathogen Pc in chestnut trees

Effect of single Quercus ilex trees upon spatial and seasonal changes in soil water content in dehesas of central western Spain

The spatial and temporal evolution of soil water content ($\theta$) in Quercus ilex dehesas has been investigated to determine how trees modify the soil water dynamics and the nature of tree-grass interactions in terms of soil water use in these ecosystems. Soil physical parameters and $\theta$ were measured at different distances from the tree trunk (2-30 m) in the upper 300 cm of soil. $\theta$ was measured monthly by TDR during 2002-2005. Tree water potential was determined during the summers of 2004 and 2005. At deeper soil layers, mean $\theta$ values were higher beyond than beneath tree canopy during dry periods. $\theta$ depletion beyond tree canopy continued even in summer, when herbaceous plants dried up, suggesting that trees uptake water from the whole inter-tree space. Results have shown a high dependence of trees on deep water reserves throughout late spring and summer, which helps to avoid competition for water with herbaceous vegetation.Effets de chênes verts isolés sur les variations spatiales et temporelles de l'humidité du sol dans les dehesas du centre-ouest de l'Espagne. L'objectif de ce travail a été de déterminer les effets de chênes verts (Quercus ilex L.) isolés sur la teneur en eau du sol ($\theta$) et la nature des interactions arbre-strate herbacée sous climat semi-aride, en terme d'utilisation de l'eau du sol dans ces écosystèmes. Les paramètres physiques du sol et $\theta$ ont été mesurés jusqu'à 300 cm de profondeur et à différentes distances (2 à 30 m) autour des arbres. $\theta$ a été mesurée par TDR, mensuellement de 2002 à 2005 dans quatre dehesas. Le potentiel hydrique des arbres a été mesuré durant les étés 2004 et 2005. Essentiellement en profondeur et en été, les valeurs moyennes de $\theta$ furent plus élevées au-delà de la canopée que sous les arbres. La diminution de $\theta$ au-delà de la canopée des arbres a continué à diminuer encore en été lorsque les plantes herbacées étaient sèches, suggérant un prélèvement d'eau par les arbres. Nos résultats suggèrent alors que les arbres peuvent utiliser de l'eau localisée loin deux même à des distances de 20 m. et qu'ils sont très dépendants des réserves d'eau en profondeur (100-300 cm) pendant la fin du printemps et en été, ce qui contribue à diminuer la concurrence pour l'eau entre arbres et strate herbacée

Selección de árboles Plus de Pinus pinaster tolerantes a Armillaria ostoyae

1 página.-- Trabajo presentado en Vitoria (España) en septiembre-octubre de 2010.Peer reviewe

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

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

Multiple resistances against diseases and insects in a breeding population of Pinus pinaster

Peer reviewe

Effect of grafting on phenology, susceptibility to Phytophthora cinnamomi and hormone profile of chestnut

Ink disease caused by the root-rot pathogen P. cinnamomi (Pc) threatens European sweet chestnut (Castanea sativa Mill.) orchards, and growers increasingly graft susceptible C. sativa traditional varieties on Pc-resistant hybrid commercial rootstocks. The influence of the scion, the rootstock, and grafting per se on the vegetative budburst, growth, susceptibility to Pc and defence-related hormone profile of Castanea spp. are unknown. In a greenhouse experiment, these effects were evaluated by reciprocally grafting two Pc resistant C. crenata x C. sativa clones and two Pc susceptible C. sativa clones. Resistance to Pc and the hormone content of leaves and roots were rootstock-dependent, and survival rates of susceptible chestnuts strongly increased when grafted on resistant rootstocks. The scion had no effect on the resistance to Pc and the hormone profile of leaves and roots of grafted trees, but influenced vegetative budburst and primary growth. Grafting per se increased susceptibility to Pc and altered the defence-related phytohormone content of trees, especially in resistant rootstocks, but did not influence budburst and growth of trees. Grafting-induced alteration of the constitutive defense-related hormone profile could explain the increased susceptibility of resistant rootstocks to Pc. Nine days after infection, a dynamic hormonal response consisting of decreased jasmonates (JA and JA-Ile) in leaves and increased ABA and JA-Ile in roots was observed in resistant chestnuts. This is the first study addressing the role of grafting in modulating resistance to the soil-borne pathogen Pc in chestnut trees.La enfermedad de la tinta causada por el patógeno de la pudrición de la raíz P. cinnamomi (Pc) amenaza los huertos de castaños dulces europeos (Castanea sativa Mill.), y los productores injertan cada vez más variedades tradicionales de C. sativa susceptibles en portainjertos comerciales híbridos resistentes a Pc. La influencia del vástago, el patrón y el injerto per se en la brotación vegetativa, el crecimiento, la susceptibilidad a Pc y el perfil hormonal relacionado con la defensa de Castanea spp. son desconocidos En un experimento de invernadero, estos efectos se evaluaron injertando recíprocamente dos clones de C. crenata x C. sativa resistentes a Pc y dos clones de C. sativa susceptibles a Pc. La resistencia a Pc y el contenido hormonal de hojas y raíces dependieron del portainjertos, y las tasas de supervivencia de los castaños susceptibles aumentaron considerablemente cuando se injertaron en portainjertos resistentes. El vástago no tuvo efecto sobre la resistencia a Pc y el perfil hormonal de hojas y raíces de árboles injertados, pero influyó en la brotación vegetativa y el crecimiento primario. El injerto per se aumentó la susceptibilidad a Pc y alteró el contenido de fitohormonas relacionadas con la defensa de los árboles, especialmente en portainjertos resistentes, pero no influyó en la brotación y el crecimiento de los árboles. La alteración inducida por el injerto del perfil hormonal relacionado con la defensa constitutiva podría explicar la mayor susceptibilidad de los portainjertos resistentes a Pc. Nueve días después de la infección, se observó en castaños resistentes una respuesta hormonal dinámica consistente en una disminución de los jasmonatos (JA y JA-Ile) en las hojas y un aumento de ABA y JA-Ile en las raíces. Este es el primer estudio que aborda el papel del injerto en la modulación de la resistencia al patógeno del suelo Pc en castaños.This work was funded by grant AGL2014-53822-C2-1-R from the Ministerio de Economía y Competitividad (Spain), and the European Regional Development Fund (FEDER) from the European Union. supported by a grant ‘Margarita Salas para la formación de jóvenes doctores’ from the Universidad de Extremadura (Spain).peerReviewe

Cross-resistance against diseases and insects in a breeding population of Pinus pinaster

Peer Reviewe

Atacados por todos los flancos: defensas cruzadas de los pinos frente a sus múltiples enemigos

Trabajo presentado como póster al Congreso forestal “Bosques de futuro” celebrado en Orense entre el 25 y el 26 de mayo de 2011Las plantas se defienden de sus enemigos con distintas defensas mecánicas y químicas cuya maximización simultánea podría estar comprometida. En especies de vida larga y de gran tamaño, como los pinos, la teoría predice que la evolución favorece defensas de tipo generalista, eficaces frente a un amplio abanico de enemigos, que actúan de forma cuantitativa reduciendo la palatabilidad de los tejidos, y con ello la eficacia biológica de sus enemigos. En la literatura, sin embargo, no existen evidencias de esta supuesta resistencia cruzada. En esta comunicación integramos los resultados de distintos experimentos independientes realizados con el mismo material genético para determinar si existe correlación genética positiva en la resistencia a distintas plagas y enfermedades, y si ésta está relacionada con caracteres cuantitativos de defensa y con otros caracteres fenotípicos, como la productividad o el esfuerzo reproductor. El trabajo se centra en una submuestra de la población de mejora del programa de mejora genética de Pinus pinaster de Galicia-Costa. El material consiste en 39 familias de medios hermanos de árboles sobresalientes seleccionados en la región de procedencia Galicia-Costa, que se encuentran representados en los huertos semilleros clonales de primera generación del programa. En esta comunicación hemos recopilado la información de distintos experimentos de campo y de invernadero destinados a evaluar la variación genética en resistencia a distintas patologías. Los patógenos considerados son Fusarium circinatum, F. oxysporum y Armillaria ostoyae, y los insectos evaluados son Thaumetopoea pithyocampa, Hylobious abietis y Dioryctria sylvestrella; todos ellos causan importantes daños a las masas de P. pinaster en la zona. Los caracteres de defensa examinados son los niveles constitutivos e inducidos del contenido en diterpenos en el tallo, y de fenoles totales y taninos condensados en las hojas. El peso del piñón, el crecimiento temprano, la producción de conos y la morfología de raíces también se han tenido en cuenta en el estudio. Las relaciones entre parámetros se evaluaron mediante correlación de Pearson entre los valores de mejora de la resistencia a cada patógeno estimados independientemente en cada experimento. También se utilizó un análisis de componentes principales para reducir la dimensionalidad de los datos, e intentar agrupar e identificar síndromes defensivos contra los que los pinos usan los mismos mecanismos de defensa. Los resultados no respaldan nuestra hipótesis inicial, y la ausencia de resistencia cruzada o crossresistance parece la norma en esta especie. Aunque algunas correlaciones positivas revelan un papel relevante de algunos de los caracteres de defensa evaluados protegiendo a las plántulas frente a determinados patógenos o plagas, las defensas químicas analizadas no pueden catalogarse como defensas generalistas eficaces frente a todos los enemigos. Así, la combinación de múltiples caracteres de defensa parece esencial para hacer frente al gran abanico de enemigos de este pino.Financiado por el Ministerio de Ciencia e InnovaciónPeer Reviewe