G. Lim

Spore density and root colonization of vesicular-arbuscular mycorrhizas in tropical soil

Spore density and mycorrhizal colonization were studied in four plant species within two sites in a lowland rain forest for a period of 17 months. Although the dominant VA endophyte and plant species examined in each site were different, the variation in spore numbers and mycorrhizal colonization in both sites showed a similar pattern. When spore numbers were high, percentage colonization was low, but as spore numbers began to decline the colonization increased. Highest spore numbers were recorded from Aug. to Oct. while most mycorrhizal colonization occurred from Dec. to March. To account for this variation, the possible interaction between the nutrient status of tropical soils and host plants with the life cycle of the VA endophytes is discussed.

Influence of spore density and extracellular conidial matrix on spore germination in Colletotrichum capsici

The influence of extracellular conidial matrix on germinability was investigated using a tropical isolate of Colletotrichum capsici . Decreasing spore density and the amount of accompanying matrix increased germinability of freshly gathered spores, especially those from C. capsici the inhibitory or retardatory role of the matrix should be considered in the context of mass survival previous to splash-dispersal.

EFFECT OF STORAGE OF INOCULUM ON SPORE GERMINATION OF A TROPICAL ISOLATE OF GLOMUS CLARUM

The storage of inoculum (mycorrhizal spores and roots in soil) as prerequisite treatment for increasing axenic spore germination was investigated with a tropical isolate of Glomus clarum. Prolonged dry storage of the inoculum, for up to 6 months at 25-30 C, increased percentage spore germination significantly on water agar. If, following dry storage, the extracted spores were then stored at 4 C for at least 2 weeks, germination was further enhanced. Incubation temperatures of 25-35 C and medium pH of 5-8 were most favorable for germination. These requirements may be significant in understanding the ecophysiology of vesicular-arbuscular mycorrhizal fungi in their natural environment.

Screening for Fungal Lipase Using Chromogenic Lipid Substrates

Several types of chromogenic lipid substrates are available, for example, those of the p-nitrophenyl or a-naphthyl groups. Since /7-nitrophenyl caprylate has been successfully used for quan? titative assay of lipase activity (Staeudinger et al, 1973), our choice of substrates falls into this group of molecules, e.g., /?-nitrophenyl caprylate (C8), /7-nitrophenyl myristate (C14), and /?-nitrophenyl palmitate (C16). Lipases showing af? finity for these substrates will hydrolyze the ester linkage between thep-nitrophenol group and the fatty acid molecule, resulting in the appearance of yellow coloration in the medium. This is due to the presence of /?-nitrophenolate anion and is most intense under alkaline conditions where it

Observations on in vitro sporulation of Glomus clarum

Following incubation at 25 °C for more than 45 days, sporulation of Glomus clarum was observed on water agar with either 20 p.p.m. or no added phosphate. Spores were borne on one or two subtending hyphae.