Radial-growth and wood anatomical changes inAbies albainfected byMelampsorella caryophyllacearum: a dendroecological assessment of fungal damage

Abstract

-The fungus Melampsorella caryophyllacearum causes serious damage on Abies alba. However, radial-growth loss caused by the fungal infection has not been quantified before. In the Spanish Pyrenees, three stands were sampled (dasometry, incidence, intensity), and cores were taken from asymptomatic and symptomatic trees for dendroecological analyses. Climate-growth correlations were assessed through correlation functions relating monthly mean temperature and total precipitation with radial growth. The incidence of the disease significantly increased with tree dominance. The maximum reduction of radial growth (20%) in symptomatic trees was observed during 1983-2002, when xylem showed frequent traumatic resin ducts. During the year before growth, the radial-growth loss was positively correlated to a wet December. In the year of tree-ring formation, growth loss was negatively correlated with minimum temperatures in February, March and April. The climatic effects on radial-growth of asymptomatic and symptomatic trees are discussed.dendroecology / fungal infection / silver fir / tree-ring width Résumé -Croissance radiale et changements anatomiques du bois chez Abies alba infecté par Melampsorarella caryophyllacearum : une évaluation dendrochronologique des dommages fongiques. Le champignon Melampsorarella caryophyllacearum cause de sérieux dommages chez Abies alba. Cependant, les pertes causées par cette infection fongique n'ont pas encore été quantifiées. Dans les Pyrénées espagnoles, trois stations ont été étudiées et des carottes de sondages ont été prises chez des arbres sans symptôme et chez des arbres présentant des symptômes pour des analyses dendrochronologies. Les corrélations croissance/climat ont été évaluées par des fonctions de corrélations reliant la température mensuelle moyenne et les précipitations totales et la croissance radiale. L'incidence de la maladie s'accroît significativement avec la dominance de l'arbre. La réduction maximale de croissance radiale (20 %) chez les arbres présentant des symptômes a été observée pendant la période 1983-2002, quand le xylème montre des traumatismes fréquents des conduits résinifères. L'année précédant la croissance, la perte de croissance radiale était positivement corrélée avec un mois de décembre humide. Dans l'année de formation du cerne, la perte de croissance était négativement corrélée avec les minima de températures en février, mars et avril. Les effets climatiques sur la croissance radiale des arbres asymptomatiques et symptomatiques sont discutés. dendroécologie / infection fongique / sapin pectiné / largeur de cerne

Canopy openings may prevent fir broom rust (Melampsorella caryophyllacearum) infections

“…Given these differences, the presence of more shade or light demanding understory plants (Ellenberg et al 1991) may be a more reliable estimator of light availability in these stands. Our results seem to follow those of Nicolotti et al (1995), who observed higher incidences of disease at wet sites, and those of Solla and Camarero (2006), who observed lower incidences of this disease in south-facing stands.…”

“…At the point of infection, the fungus induces the production of epicormic sprouts resulting in brooms, but it may also produce large galls that weaken the trunk against wind throw (Butin 1995;Montoya et al 2002) and provide a point of entrance for heart rot fungi (Shigo 1967). In addition, Singh (1978) found height and diameter growth reductions associated with broom rust infection, and Solla et al (2006) confirmed growth losses of 20% associated with the presence of this disease.…”

“…This suggests that some stands may be structurally predisposed to the disease, such as the observed pathoregion of this disease described by Solla and Camarero (2006) in the Irati forest in Spain. Predisposing conditions proposed include the proximity of stands to grasslands, rivers and open areas (Nicolotti et al 1995;Solla and Camarero 2006).…”

Alterations of the resin canal system of Pinus pinaster seedlings after fertilization of a healthy and of a Hylobius abietis attacked stand

“…After weevil attack, plants produced traumatic resin canals arranged in a ring fashion in the developing xylem. In the same way, the fungi Cronartium ribicola and Melampsorella caryophyllacearum were reported to cause changes in the cambial zone of Pinus monticola and Abies alba, respectively, including the development of cambium-derived xylem traumatic resin ducts (Hudgins et al 2005;Solla et al 2006). We were unable to distinguish among constitutive and traumatic resin canals in the xylem of the attacked P. pinaster seedlings.…”

“…Inducible defences include the increasing synthesis of antifeedant secondary compounds, such as some monoterpenes and phenolics (Klepzig et al 1995), the formation of traumatic resin ducts in the xylem (Alfaro 1995;Tomlin et al 1998;Solla et al 2006), swelling and proliferation of polyphenolic parenchyma cells in the bark (Krokene et al 2003;Franceschi et al 2000), and the formation of a wound reaction zone (Oven and Torelli 1994;Solla et al 2002). The intensity of both constitutive and induced defence mechanisms in Pinaceae depends on tree age, genotype, species, and can be also affected by environmental factors such as nutrient availability (Rosner and Hannrup 2004;van Akker et al 2004).…”