Growth of coniothyrium minitans gliocladium roseum trichoderma harzianum and trichoderma viride from alginate pellets and interaction with water availability
Magan, N.; Whipps, J.M.
Bulletin OEPP 18(1): 37-46
Conidia, chlamydospores and mycelia of Coniothyrium minitans, Gliocladium roseum, Trichoderma harzianum and T. viride were obtained from liquid or solid culture and formulated within alginate pellets. Quantitative assessment of these pellets over a 12-week period showed a decrease in the number of colony-forming units (cfu) from about 107 to 103-104 g-1 air-dried pellets. Qualitatively, growth was assessed by direct plating the alginate pellets on rich (potato dextrose agar, PDA) and poor (water agar, WA) substrates. Rate of growth (mm day-1) from individual pellets was decreased by water potential in the range -0.25 to -2.8 MPa, with growth significantly less on WA than PDA for all species except G. roseum. All species grew from 95 to 100% of direct-plated pellets on PDA over the water-potential range tested. However, on WA, interaction between water stress (-2.8 MPa) and lack of nutrients resulted in a reduction, with less than 30% of pellets of some formulations showing growth. In contrast to the quantitative results, there was little change in the growth rate of test species from pellets over a 12-week period, particularly on PDA. Growth from pellets could not be conclusively demonstrated in unsterile soil. The shelf-life and viability of alginate pellets in soil is assessed.