Field performance of Eucalyptus urophylla inoculated with an introduced and idigenous strains of Pisolithus at three sites in the Philippines

The effectiveness of an isolate of Pisolithus from Australia was compared with a Philippine Pisolithus isolate in promoting the growth of Eucalyptus urophylla on three acid (pH 4.1-5.9, 0.005M CaCl2) sites in the Philippines (Pangasinan, Bukidnon and Surigao). Isolates of Pisolithus were taken from basidiocarps collected under eucalypts growing in Western Australia and from the Philippines. Generally, the introduced Pisolithus promoted greater wood volume of E. urophylla planted in dry marginal land (Pangasinan) and in moist logged-over area (Surigao) in the Philippines than the Philippine Pisolithus isolate. Root colonization by the two fungi did not vary but there was a difference in the root colonization levels between sites implying that the prevailing microclimatic conditions on each site had affected the performance of the ECM inoculants. In this study, the number of isolates tested was limited, thus, future field trials should include a wider range of ectomycorrhizal fungi. Further work is required to determine whether the growth responses measured at the two sites (Pangasinan and Surigao) are maintained until the trees are harvested

Effects of soil pH on the ectomycorrhizal response of Eucalyptus urophylla seedlings

To examine the effects of soil pH on ectomycorrhizal formation and function on Eucalyptus urophylla S. T. Blake, seedlings inoculated with nine ectomycorrhizal fungi (seven isolates of Pisolithus spp., Scleroderma cepa and Laccaria laccata collected under eucalypt stands in Australia and the Philippines) were transplanted into pots containing a non-sterile acid (pH 4·6) sandy loam amended with four levels of CaCO3 that raised the soil pH from 4·6 to 6·6 (5 mM CaCl2). Pots were placed in temperature-controlled water baths (28 ± 2 °C) inside an evaporatively cooled glasshouse for 9 wk. Increase in soil pH from 4·6 to 6·6 significantly decreased plant d. wt and shoot nutrient content of uninoculated and inoculated seedlings. Inoculation with four Pisolithus spp. (H445, H2144, M56 and H4003) significantly increased the growth of E. urophylla seedlings at pH 4·6. At pH 6·6, eight ectomycorrhizal isolates significantly improved total d. wt compared with those of the uninoculated seedlings. Pisolithus isolates stimulated seedling growth more than L. laccata whereas S. cepa was ineffective at all pH levels. Total d. wt of H445 inoculated plants grown in P-deficient (8 mg P kg-1 soil) soil was 147% more than that of uninoculated plants given the same P rate and was 70% that of plants fertilized with 64 mg P kg-1 soil (P64) at pH 46. At soil pH 5·8 and 6·6, M56 was the best growth-promoter for E. urophylla. These results indicate that soil pH can significantly alter the development and function of ectomycorrhizal fungi. Soil pH did not significantly affect mycorrhizal formation by the different ectomycorrhizal fungi. However, the percentages of mycorrhizal root tips formed by the different ectomycorrhizal fungi differed significantly. Pisolithus isolate H445 formed the highest percentage of colonized roots and highest total d. wt at pH 4·6 and 5·2, implying its potential for commercial use in acidic conditions

Effects of chromium and nickel on growth of the ectomycorrhizal fungus Pisolithus and formation of ectomycorrhizas on Eucalyptus urophylla S.T. Blake

Effects of chromium (Cr2+) (0-100 000 μmol Cr l-1 MMN agar, supplied as CrO3) and nickel (Ni2+) (0-100 000 μmol Ni l-1 MMN agar, supplied as NiCl2) cations on growth of the ectomycorrhizal fungus Pisolithus, collected from under eucalypts growing in Western Australia, the Philippines and New Caledonia were studied in vivo. The effects of these heavy metals on mycorrhizal formation with Eucalyptus urophylla S.T. Blake were also examined in vitro. Nickel was more toxic to fungal growth and ectomycorrhiza formation than Cr. Substrate levels of Ni greater than 20 μmol l-1 agar and Cr levels greater than 200 μmol l-1 agar decreased mycelial dry weights except for the Australian isolate where mycelial dry weight at harvest was not affected by Cr. Nickel and Cr rates greater than 200 and 2000 μmol l-1, respectively, prevented fungal growth. The fungi differed in their tolerance to the heavy metals and isolates from the Philippines and New Caledonia grew at higher Ni levels than the Australian isolate. Media concentrations of 1000 μmol Cr l-1 and 80 μmol Ni l-1 reduced the percentage of root tips colonized by the fungi. Inoculation with the New Caledonian isolate prevented the appearance of foliar toxicity symptoms in seedlings grown at 80 μmol Ni l-1 agar. The effects of three rates of Ni (0, 30 and 60 μmol Ni kg-1 soil) on the formation of ectomycorrhizas and growth of E. urophylla seedlings in a yellow sand were examined in a glasshouse. The application of Ni reduced the percentage of root tips colonized at week 4, from 12% in the nil treatment to 3% at 60 μmol Ni kg-1 soil, but there was no effect at week 12. The New Caledonian isolate produced the greatest percentage of ectomycorrhizas in all Ni levels (85% at 0, 81% at 30 and 75% at 60 μmol Ni kg-1 soil) and was the only isolate that promoted an increase (5 times the uninoculated treatment) in seedling total biomass at 60 μmol kg-1 soil. Hence, the isolate from a heavy metal-contaminated site not only colonized a greater percentage of root tips in vitro, but it was more effective in promoting seedling total biomass in Ni-amended soils than the other isolates. By contrast, the good performance of the Philippine isolate in vitro, in terms of plant biomass and growth rate of mycelia, was not reflected in its capacity to form mycorrhizas and promote plant growth in vivo. This study indicates the importance of undertaking preliminary screening of ectomycorrhizal fungi for heavy metal tolerance under in vivo conditions before further testing in field soils of ultramafic origin

Soil fumigation and phosphorus supply affect the formation of Pisolithus-Eucalyptus urophylla ectomycorrhizas in two acid Philippine soils

To examine the effects of microbial populations and external phosphorus supply of two Philippine soils on mycorrhizal formation, Eucalyptus urophylla seedlings were inoculated with two Pisolithus isolates and grown in fumigated, reinfested and unfumigated soil fertilized with four rates of phosphorus. The Pisolithus isolates used were collected from under eucalypts in Australia and in the Philippines. Soils were infertile acid silty loams collected from field sites in Pangasinan, Luzon and Surigao, Mindanao. Significant interaction was observed between inoculation, soil fumigation and phosphorus supply on mycorrhizal formation by the Australian isolate in Surigao soil but not in Pangasinan soil. Soil fumigation enhanced mycorrhizal formation by the Australian isolate but did not affect root colonization by the Philippine isolate. Root colonization by the Australian isolate was highest in the reinfested soil while for the Philippine isolate it was highest in the unfumigated soil. The Australian isolate was more effective than the Philippine isolate in promoting growth and P uptake of E. urophylla seedlings in both soils. Total dry weight and P uptake of E. urophylla seedlings inoculated with the Australian isolate were maximum in fumigated and in the reinfested Pangasinan and Surigao soils supplied with 8 mg P kg-1 soil. In the unfumigated soil, growth of seedlings inoculated with the Australian isolate was significantly reduced. Seedlings inoculated with the Philippine isolate had the largest dry weights and P contents in unfumigated Pangasinan and Surigao soils supplied with 8 mg P kg-1 soil. These results indicate that the performance of the Australian Pisolithus isolate was markedly affected by biological factors in unfumigated soil. Thus, its potential use in the Philippines needs to be thoroughly tested in a variety of unfumigated soils before its widespread use in any inoculation programme

Nursery training for smallholders: An evaluation of two extension programs in the Philippines

High-quality seedlings are a prerequisite for successful forestry and agroforestry expansion in developing countries. Unfortunately, in the central Philippines, as supplies of timber from native forest have diminished in recent years, the expansion in planting of timber trees has been retarded by sub-optimal production of seedlings from small-scale nurseries. To address this problem, an extension program supported by the Australian Centre for International Agricultural Research (ACIAR) has attempted to improve the quality of seedlings produced in home nurseries, by assisting smallholders to raise and out-plant seedlings. A complementary program undertaken as part of the Community Agricultural Technology Program (CATP) has attempted to provide community workers and managers of small-scale nurseries with the benefit of recent ACIAR nursery research. Extended assistance in the ACIAR program addressed smallholders’ low self-efficacy in nursery technology and was successful in assisting them to grow high quality seedlings. A limited program of assistance was relatively unsuccessful. Evaluation of the CATP program showed that prior to the training, CATP participants were unfamiliar with some aspects of basic nursery technology. Consequently, they may have been unable to provide competent advice to smallholders. This implies that—as with the ACIAR training—extended training and follow-up assistance may be the key to improving the quality of seedlings for forestry and agroforestry expansion in the central Philippines