Eight endophytic fungi were isolated from roots of the threatened terrestrial orchid, Pecteilis susannae (L.) Rafin. Phylogenetic analysis based on an alignment of internal transcribed spacer regions of nuclear rDNA indicated that seven isolates belonged to the genus Epulorhiza and one to Fusarium. All fungal isolates were cultured with orchid seeds collected from three field sites near Doi Suthep-Pui National Park, Chiang Mai, Thailand. Seed germination and protocorm development were evaluated up to 70 days after sowing. Percent symbiotic seed germination was highest (86.2%) when seeds were cultured with Epulorhiza (CMU-Aug 013). The protocorm development was the most advanced up to stage 2, continued embryo enlargement, or rupture of the testa, and the highest percentage was 17.8% when seeds were cultured with Epulorhiza (CMU-Aug 007). Without fungi, seed germination and protocorm development were 62.1% and 11.1%, respectively. The dependency of P. susannae on fungal symbionts for early seedling development is yet to be determined. Optimizing seed germination and seedling fitness will assist the conservation of this threatened orchid in Thailand.

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Symbiotic seed germination of Pecteilis susannae (L.) Rafin was investigated using 11 fungal isolates recovered from roots of four Thai terrestrial orchids (P. susannae, Eulophia spectabilis, Paphiopedilum bellatulum and Spathoglottis affinis). Seed germination and protocorm development were evaluated up to 133 days after sowing. Protocorm development was most advanced, up to stage 5 (elongation of the first leaf), when seeds were cultured with 4 Epulorhiza isolates obtained from roots of P. susannae (CMU-Aug 028, 4.3%, CMU-Aug 007, 4.2%, and CMUAug 013, 2.2%) and E. spectabilis (CMU-STE 014, 3.9%). Moreover, stage 4 protocorm development (emergence of the first leaf) occurred with fungal isolates CMU-STE 011, 5.7%, (Epulorhiza sp.) and CMU-AU 212, 4.3%, (Tulasnella sp.) obtained from roots of E. spectabilis and S. affinis respectively. When seed was incubated without fungi (control), development was limited to stage 3 of protocorm development (appearance of promeristem). This is the first report of protocorm stage 5 development in P. susannae using compatible fungal symbionts. Optimization of seed germination and seedling fitness will assist the conservation and propagation of this orchid species and other terrestrial orchids in Thailand.

Calcined clay pellets are popular planting material for those who love to grow plants in pots. The calcined clay pellets consist of clay (C), phosphate rock (PR), and rice husk ash (RHA). [(1-x)(50C–50PR)-xRHA], x(RHA) = 0, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, and 0.65 wt% were prepared by a conventional solid-state reaction method. The samples were made into a spherical shape with a diameter of 10 mm and fired at 600℃ to 1000℃. The effect of x contents on phase formation, microstructure, and chemical properties of [(1-x)(50C–50PR)-xRHA] was studied. X-ray diffraction revealed the typical assemblages with quartz, illite, and kaolinite in all the samples. SEM images of samples showed irregular packing and a highly porous microstructure. The addition of x(RHA) contents results in porous microstructure in all the samples. The surface area and pore volume of samples increased from 8.83 m2·g-1 to 14.71 m2·g-1 and 0.938 cm3·g-1 to 0.942 cm3·g-1, respectively, with the increase of x(RHA). The density of the samples slightly decreased from 2.45±0.06 g·cm-3 to 1.94±0.05 g·cm-3, with an increase in x(RHA) contents. The capability of calcined clay pellets to immobilize plant growth-promoting fungi was then studied. The results showed that orchid endophytes, as plant growth-promoting fungi, grow well on the calcined clay pellets saturated with potato dextrose broth (PDB). Besides, all fungi can live on calcined clay pellets and stay viable for at least 35 days after inoculation. These results suggested that the calcined clay pellets could serve as planting material that enhances plant growth (via its nutrients and growth-promoting fungi) simultaneously.