Dynamics of ectomycorrhizal fungi in an Eucalyptus globulus plantation: Effect of phosphorus fertilization

Eucalyptus globulus is the most widely planted temperate eucalypt in regions of Mediterranean climate. Plantations in Western Australia (WA) are common on sandy soils where fertilization is necessary (especially N, P, K and Cu) to sustain high growth rates. Ectomycorrhizal (ECM) fungi are common in these plantations and are probably ecologically important in nutrient cycling. Whether fertilization with phosphorus (P) could alter fungal dynamics in these plantations is investigated in this study. Three rates of P (nil, low = 100 kg P ha-1 and high = 1000 kg P ha-1), including basal nutrients, were applied to a 4-years-old E. globulus plantation in WA and the following measured over a 2 years period: fungal diversity, fungal biomass, soil hyphal production, tree biomass, litter production, and accumulation of N, P, K and Cu in the fungal and tree components. The addition of P reduced the number of basidiocarps by 5 (low P)-14% (high P), basidiocarp and soil hyphal biomass by 26-40% and 29-44%, respectively, without affecting above-ground ECM fungal diversity, species of Laccaria, Pisolithus and Scleroderma. There was no response in whole tree biomass or litterfall to P, but low P increased fine root biomass in ingrowth cores at 6 months to 364 kg ha-1. Accumulation of N, P, K and Cu generally declined in fungi and litterfall with P, but increased in tree biomass (except N and Cu). The total nutrient load was in the order: above-ground tree > soil hyphae > below-ground tree > litter > fine root > basidiocarp. The combined nutrient pool in the fungal component was approximately 10% of that in the tree. This illustrates the potential significance of ECM fungi in immobilizing P and other nutrients, and in their subsequent cycling during fungal decomposition in plantations. The impact of P on fungal dynamics therefore requires consideration when applying fertilizers in eucalypt plantations

Dynamics of ectomycorrhizal fungi in a Eucalypus urophylla S.T.Blake plantation in the Philippines: Effect of phospohorus fertilization

Commercial plantations in the Philippines may benefit from fertilization and mycorrhizal application. Work in temperate forestry suggests that phosphorus (P) addition can alter dynamics of ectomycorrhizal (ECM) fungi in eucalypt [Eucalyptus spp.] plantations. To investigate P effects on fungal dynamics, P (0, 100, and 1000 kg P ha-1) was applied to a 19-month E. urophylla plantation in Mindanao and the following quantified: biomass of basidiocarps, soil hyphae, fine roots, tree and litter, and their NPK content. Diversity of ECM fungi was low and biomass production was in the order: Scleroderma>Thelephora>Cortinarius. Hyphal growth decreased with increasing P supply. There was no response in tree growth or litter production to P. The soil hyphae were significant reservoirs of below-ground N, P and K. The nutrient content of trees above-ground was approx. equal to the sum of the nutrient load in roots, litter and ECM fungi. It was estimated that the ECM basidiomes and soil hyphae accounted for only 1-2% of the inorganic nutrients in the whole tree. The response of mycorrhizal fungi to fertilizer should be investigated in longer-term studies in the Philippines. The low fungal biodiversity and basidiome biomass were probably due to previous land use and the introduction of an exotic tree. The eucalypt plantation was established on an Imperata grassland, formerly a rainforest dominated by dipterocarps

Formação de ectomicorrizas por monocários e dicários de Pisolithus sp. e interações nutricionais em Eucalyptus grandis Formation of ectomycorrhizae by monokaryons and dikaryons of Pisolithus sp. and nutritional interactions in Eucalyptus grandis

A germinação de basidiósporos de Pisolithus spp. dá origem a monocários, caracterizados por possuírem um único núcleo haplóide por célula. No campo, o eucalipto associa-se a micélios dicarióticos de Pisolithus spp., não havendo relatos sobre a capacidade dos monocários em estabelecer a associação ectomicorrízica com a planta hospedeira nessas condições. Embora os monocários de Pisolithus sp. sejam capazes de formar a associação ectomicorrízica in vitro, nada se sabe sobre a capacidade dessas estirpes em promover a absorção de nutrientes e o crescimento do eucalipto. O objetivo deste trabalho foi estudar a formação de ectomicorrizas por isolados monocarióticos e dicarióticos de Pisolithus sp. em Eucalyptus grandis, sob condições de casa de vegetação, bem como investigar as relações entre o estabelecimento da associação e o crescimento e a absorção de P, Ca, Mg, K, Cu e Zn pelas plantas. Caracterizou-se, também, a produção de massa seca micelial e a absorção de nutrientes pelos isolados fúngicos in vitro. Os isolados monocarióticos e dicarióticos testados variaram na produção de massa seca micelial e na capacidade de absorção de nutrientes. Em geral, os monocários apresentaram maiores índices de eficiência de utilização de nutrientes do que os dicários. Todos os isolados monocarióticos e dicarióticos formaram ectomicorrizas típicas quando associados com E. grandis. A presença dos isolados fúngicos monocarióticos associados às raízes laterais resultou em aumento do diâmetro radial das células da epiderme radicular, característico das ectomicorrizas de eucalipto, indicando que os monocários, à semelhança dos dicários, são capazes de produzir reguladores de crescimento. As médias de percentagem de colonização das raízes pelos isolados monocarióticos e dicarióticos variaram de 12 a 76 %. A absorção de Ca, Mg e K foi estimulada de forma expressiva pela presença das ectomicorrizas, com aumentos de até 760 vezes, demonstrando a relevância dessa associação no suprimento desses macronutrientes, especialmente o Ca. Alguns isolados monocarióticos são tão eficientes quanto os dicários na colonização radicular e na absorção de nutrientes. A caracterização dos monocários de Pisolithus sp. é necessária para se estabelecer a seleção e o cruzamento dos isolados com características desejáveis, visando ao melhoramento genético e à maior eficiência da associação simbiótica. Este trabalho constitui o primeiro relato das interações nutricionais entre monocários de Pisolithus sp. e a planta hospedeira.<br>The germination of Pisolithus spp. basidiospores originates monokaryons, characterized by having a single haploid nucleus per cell. In the field, eucalypts are associated with dykaryons of Pisolithus spp., there being no reports on the capacity of monokaryons to establish the ectomycorrhizal association with the host plant under such conditions. Although Pisolithus spp. monokaryons have been shown to form ectomycorrhizas in vitro, there is no information on the ability of these strains to promote nutrient uptake and growth of eucalypts. The objective of this study was to investigate the formation of ectomycorrhizae by monokaryotic and dikaryotic isolates of Pisolithus sp. in Eucalyptus grandis under greenhouse conditions, and the relationships between the establishment of ectomycorrhizae and the host plant growth and uptake of P, Ca, Mg, K, Cu, and Zn. The fungal isolates were highly variable in dry mycelial mass production and in their ability to take up macro- and micronutrients. Generally, the nutrient use efficiency of monokaryons was higher than that of dikaryons. All tested monokaryotic and dikaryotic isolates were able to form typical ectomycorrhizae when associated with E. grandis. The presence of monokaryotic isolates associated with the lateral roots of E. grandis resulted in typical increases in the radial diameter of the root epidermal cells, characteristic of eucalypt ectomycorrhizae, indicating that monokaryons, similarly to dikaryons, are capable of producing growth regulator compounds. The mean root colonization percentage of the monokaryotic and dikaryotic isolates varied from 12 to 76 %. The Ca, K, and Mg uptake was highly stimulated by the presence of ectomycorrhizae, with up to 760-fold increases, suggesting that the association must play a significant role in supplying the host with these nutrients, especially Ca. Some monokaryotic isolates are as efficient as the dikaryons at promoting root colonization and nutrient uptake. The characterization of Pisolithus sp. monokaryons is a basic requirement for the selection and crossing of isolates with desirable traits, aiming at the genetic improvement of fungal strains and a higher efficiency of the ectomycorrhizal association. This is the first report on the nutritional interactions between Pisolithus sp. monokaryons and the host plant