Abstracts |
Bahia grass [Paspalum notatum] roots were inoculated with the arbuscular mycorrhizal fungi Glomus aggregatum (Ga), G. etunicatum (Ge), G. mosseae (Gm) and Acaulospora scrobiculata (As) every 2 weeks for one year. The spores of these fungi were placed on membrane filters which were then embedded in sterilized sand and incubated at 20, 24, 28 or 32 degrees C. Results show that all 3 species of Glomus were capable of infecting bahia grass roots and forming mycorrhiza all year. A. scrobiculata was able to form good mycorrhiza only when bahia grass roots were inoculated from May to September. When roots were inoculated on the other months of the year, mycorrhizal formation by this fungus was very poor or none at all. The inoculation periods favourable for spore production were January-April for Ga, January-April and August-September for Ge, May-October for Gm, and May to mid September for As. During these periods, the average number of spores per 100 g of soil produced by Ga, Ge, Gm and As were 54, 4024, 1019 and 2010, respectively. The temperature range suitable for germination was broader 20-32 degrees C for Ga and Ge. High germination rates occurred at 28 and 32 degrees C for Ga, and 20, 24 and 32 degrees C for Ge. As the temperature increased, the time needed to obtain high germination rate decreased. The optimum temperature for the spore germination of Gm and As was 28 degrees C, but germination rates were low for As for the 4 temperatures tested. The ability of the 3 Glomus species to infect bahia grass roots and produce spores all year round can be due to the broad temperature range for their spores to germinate. The factors required for high germination rate of As needs further study. |