MYCORRHIZAL COLONIZATION IN NATIVE AND DOMESTICATED NOTHOFAGUS NERVOSA (RAULÍ)

FERNÁNDEZ NATALIA; FONTENLA SONIA

Pucón

Workshop; 3rd International Workshop: Advances in science and technology of bioresources; 2011

Universidad de la Frontera

Mycorrhizas are mutualistic associations between soil fungi and plant roots, they influence plant growth, nutrient uptake, and provide a greater area for interactions with other soil microorganisms. In temperate and boreal forests, the establishment, growth and survival of different tree species are usually dependent on colonization by ectomicorrhizas (ECM). Nothofagus nervosa (Raulí) is an ecologically and economically important species of South American temperate forests. In Argentina, this species has a reduced natural distribution area, mainly due to its overexploitation in the past. This critical situation led to the implementation of conservation and domestication programs. Tree domestication refers to how humans select, manage and propagate species in order to increase its growth rate, disease resistance or wood quality. Among the different aspects that should be considered in these programs, are the ECM associated with this species, since nursery inoculation with suitable ECM would be important for the successful establishment of outplanted seedlings. The aim of our project is to analyze the abundance and diversity of ECM in N. nervosa, to compare them between native and nursery cultivated individuals and finally to select some ECM strains which would have significant application in domestication processes. In this context, the starting point is the quantification and characterization of the ECM associated with native and nursery cultivated N. nervosa. For evaluating the mycorrhizal status of seedlings that are going to be taken to the field, a two-year trial was conducted. It consisted in sowing N. nervosa seeds and then analyzing seedlings´ roots at different times in order to quantify ECM and to determine its diversity. In the forest, native as well as nursery cultivated individuals corresponding to two field trials, one established within a native forest and the other beneath a Pinus plantation, were studied. Five trees of each category were randomly selected. The complete root system of native and nursery cultivated seedlings were studied, while 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 were quantified and classified in different groups according to its macromorphology. ECM were observed in every sample and different morphotypes were observed. In the native forest, more than 90% of the root tips examined per plant were colonized and 22 morphological groups were described. Cultivated seedlings and young nursery cultivated plants established under the exotic plantation showed a significantly lower colonization (~65%) and only 4 ECM groups or morphotypes were observed in both groups of plants. Thus, ECM abundance and composition is influenced by the place where the plants are growing, being the percentage values and the biodiversity much higher in the native forest. This work constitutes the initial step in the study of ECM in N. nervosa and provides the basis for further investigations related to their possible application in domestication programs, such as the influence of ECM inoculation on seedling survival and growth after being planted in the field and their interaction with other soil microorganisms.