CALIDAD MORFOLÓGICA Y BIOLÓGICA DE Pinus radiata D. Don, MICORRIZADO CON Scleroderma verrucosum (Vaill) Pers. Y Rhizopogon luteolus Fr. & Nordh. EN CONDICIONES DE VIVERO

Se evaluó el efecto de Scleroderma verrucosum (Vaill) Pers y Rhizopogon luteolus Fr. & Nordh. sobre la calidad morfológica y biológica de plantas de Pinus radiata D. Don en vivero en Vilcashuamán, Ayacucho, Perú. Tratamientos: (1) Micorrización con Scleroderma verrucosum, (2) Micorrización con Rhizopogon luteolus, (3) Mezcla de ambos hongos y (4) Control, en un diseño completamente al azar con 10 repeticiones por tratamiento. Los hongos provinieron de bosques de Pinus radiata y Eucalyptus globulus de la localidad. La inoculación se realizó en el repique a los 30 días de siembra y la evaluación a los 7.5 meses después del repique. Los pinos micorrizados superaron con diferencias significativas al control en todas las variables. En el diámetro del cuello y materia seca de la parte aérea de los inoculados no presentaron diferencias significativas; sin embargo, en altura, materia seca de la raíz y materia seca total destacó el tratamiento Mezcla. En la calidad biológica se observó mayor número de micorrizas en los inoculados, con diferencias significativas frente al control sin micorrizar. Se evidenció mayor porcentaje de micorrizas monopodiales (91%) en relación a los dicotómicos (8.5%) y coraloides (0.6%). Se determinaron relaciones positivas significativas entre las variables morfológicas, pero éstas sobre P. radiata presentaron asociaciones no significativas con el número de micorrizas. El uso individual y en mezcla de hongos ectomicorrízicos silvestres incrementó la calidad morfológica y biológica de P. radiata, por ello se recomienda la aplicación de estos hongos para la producción de plántulas en viveros de Vilcashuamán y otras zonas altoandinas.

Ectomycorrhizal Fungi Associated with Pinus densiflora Seedlings under Flooding Stress

Flooding is an environmental stress for plants that not only limits aeration and nutrient acquisition, but also disturbs underground plant-associated fungal communities. Despite frequent flooding, red pine (Pinus densiflora) seedlings thrive in streamside environments. However, whether the compatible ectomycorrhizal fungi (EMF) of red pine are affected by natural flooding is unclear. As EMF are vital symbionts for the development of many trees and allow them to overcome various environmental stresses, in this study, the EMF species associated with red pine seedlings in a streamside environment in Korea were investigated after flooding. The EMF species in 47 seedlings collected from the streamside site were identified by observing their different morphotypes using internal transcribed spacer sequence analysis, and a total of 10 EMF species were identified. The EMF species diversity was lower than that in samples collected from a nearby forest analyzed as a control. The dominant EMF species of streamside seedlings included Amphinema spp., Rhizopogon luteolus, Suillus luteus, and Thelephora terrestris. This study could serve as a basis for investigating the mechanisms by which advantageous EMF aid plant development under flooding stress.

In vitro GROWTH OF ECTOMYCORRHIZAL FUNGI ASSOCIATED WITH Pinus radiata PLANTATIONS IN CHILE

A comparative study of in vitro growth of three species of ectomycorrhizal fungi (ECMF) (Rhizopogon luteolus, Suillus granulatus and Suillus luteus) was performed. Fungal material was collected in adult Pinus radiata plantations. Isolation and purification of the strains were performed on potato-dextrose-agar medium and the evaluation of the radial growth rate and the increase in mycelial biomass, under different culture conditions, was performed on the Modified Melin Norkrans growth medium. The effects of temperature (24, 28 and 32 ºC) and pH (4.8, 5.3, 5.8, 6.3 and 6.8) of the growth medium were tested for the three fungal species in two independent assays. The results indicate that the temperature had a significant effect on the radial growth rate (RG) and mycelial biomass increase (MB) in all of the evaluated fungal species. The highest RGR and MBI were recorded in R. luteolus, and the lowest values for these variables were registered in S. luteus. Rhizopogon luteolus had the highest sensitivity to pH changes. Meanwhile, there was no pattern in S. granulatus and S. luteus growth response under different pH conditions. When cultivated in vitro, the three studied species of ECMF presented adaptation, exponential, declining and stationary growth phases. The in vitro growth responses recorded in the present study showed the great potential of R. luteolus to be used in future programs using mycorrhizal inoculation in the production of Pinus radiata trees in nurseries in Chile.

Enzymatic activity of myccorrhizal fungi

The investigations included assays of enzymatic activity of ectomycorrhizal fungi from the genera: <i>Amanita, Cenococcum, Coltricia, Hebeloma, Lactarius, Rhizopogon, Russula, Suillus, Tricholoma</i> and the pine ectendomycorrhizal strain MrgX. Among the 22 investigated strains of fungi 18 could decompose starch, 14 urea, 11 asparagine, 7 protein, 6 pectin and 3 ce1lulose. The most varied enzyme activities were found in <i>Amanita muscaria, A. verna, Hebeloma, mesophaeum</i>, ectendomycorrhizal isolate MrgX, <i>Rhizopogon luteolus</i> and <i>Suillus bovinus</i>, the highest cellolotytic activity was shown by the ectendomycorrhizal strain.

Nutritional-Value of Hypogeal Fungal Sporocarps for the Long-Nosed Potoroo (Potorous-Tridactylus), a Forest-Dwelling Mycophagous Marsupial

Although mycophagy (fungus-feeding) is widespread among small ground-dwelling mammals, there has been little evaluation of the nutritional benefits of this feeding habit. In Australia, some members of the Potoroidae (or rat-kangaroo family) consume large amounts of hypogeal fungi throughout the year. Hypogeal fungi appear to be of marginal nutritional quality for small mammals with simple stomachs but potoroos have an enlarged forestomach in which microbial fermentation takes place, and this may allow more effective utilisation of protected nitrogenous components and structural carbohydrates of fungi. In a feeding experiment, we evaluated the nutritional value of sporocarps of the hypogeal fungi Mesophellia glauca (Mg) and Rhizopogon luteolus (R1), for the long-nosed potoroo (Potorous tridacytlus). Although the concentration of nitrogen was high in both fungi, much of that nitrogen was in non-protein form or associated with cell walls and may be either of low nutritional value or protected from digestive enzymes. The concentration of cell-wall constituents (fibre) was high in both fungi, suggesting low availability of digestible energy. Despite these features, the digestibilities of dry matter (Mg 86%, Rl 80%), ingested nitrogen (Mg 72%, Rl 72%) and energy (kJ kg-1) (Mg 93%, Rl 76%) of both fungi were high. Consequently, P. tridactylus maintained positive nitrogen balance and high intakes of digestible and metabolisable energy. We conclude that the sporocarps of hypogeal fungi represent a nutritionally valuable food for rat-kangaroos and suggest that lack of a foregut-fermentation strategy in other similar-sized ground-dwelling mammals in the forests of south-eastern Australia explains why they use the hypogeal fungal resource to a lesser extent than do rat-kangaroos.