Ectomycorrhizas ... Does age matter?.

FERNANDEZ N,; FONTENLA, S; GALLO, L A; MARCHELLI, P

Pucon, Chile

Congreso; 5th International Symposium of Interactions of Soil Minerals with Organic Components and Microorganisms; 2008

Mycorrhizas, mutualistic associations between soil fungi and plant roots, form a key component of soil microbial populations. They influence plant growth and uptake of nutrients, and provide a greater area for interactions with other microorganisms in the rizosphere, such as soil yeasts. Usually, in temperate and boreal forests, the establishment, growth and survival are dependent on colonization by ectomicorrhizas (ECM). Nothofagus nervosa (Raulí) is an ecologically and economically important species of South American temperate forests. In Argentina, it has a reduced natural distribution area and due to its high wood quality it was overexploited in the past. This critical situation led to the implementation of conservation and domestication programs. Among the different aspects that should be considered in these programs are the ECM and yeasts associated with this species, which are of great importance for plant growth and for their subsequent implantation in the field.The general aim of the project is to analyze the abundance and diversity of ECM and yeasts in N. nervosa, to compare them between native and nursery cultivated individuals and finally to select some mycorrhizas and yeasts strains which would have significant application in domestication processes. In this context, the starting point is the quantification and characterization of ECM. Hence, the specific aim was to analyze the percentage of root tips colonized by ECM in N. nervosa belonging to four plant categories: seedlings, young and old native individuals and young cultivated nursery individuals. During spring 2007, 5 individuals of each category were randomly selected from a stand of the natural  forest and from a nursery trial in Patagonia, Argentina. Seedlings were carefully removed with a shovel and the rest of the plants were sampled by taking 3 soil cores per tree. Samples were wrapped in plastic bags and stored at 4°C. Roots were sieved from the soil cores, carefully washed and then ECM colonization was quantified.ECM were observed in every sample. At least 95% of the root tips examined per plant had formed ECM. There were no significant differences in the percentage of root tips colonized by ECM among the four analyzed plant categories or within each of them. These results agree with some other authors which have suggested that the development of ECM do not depend on the age of the tree.This work constitutes the first description of the influence of tree age on ECM colonization in a forest of Patagonia. Besides this, this study constitutes the initial step in the analyses of ECM in N. nervosa and provides the basis for further investigations, such as yeasts-mycorrhizas interactions and possible applications of these microorganisms in conservation and domestication programs..