Growth of Coniothyrium minitans, Gliocladium roseum, Trichoderma harzianum and T. viride from alginate pellets and interaction with water availability¹

Abstract

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.

Effect of Media on Growth and Interactions Between a Range of Soil‐borne Glasshouse Pathogens and Antagonistic Fungi

“…This has already been done for other isolates directly (Wells, Bell & Jaworski, 1972;Beagle-Ristaino & Papavizas, 1985), or after forming alginate pellets which are easy to handle (Fravel et al, 1985 ;Lewis & Papavizas, 1985), to enable proliferation of the fungi to occur in the soil volume as a whole. This latter rocedure may, however, have some drawbacks in that germination from alginate pellets may be slow, particularly under low water potential (Magan & Whipps, 1987). Similarly, incorportion on the seed coat or roots could protect the underground parts and maximize the chances of protection when pathogen propagules are encountered (Lutchmeah & Cooke, 1985;Lifschitz, Windham & Baker, 1986).…”

The importance of water potential range tolerance as a limiting factor onTrichodermaspp. biocontrol ofSclerotinia sclerotiorum

“…Water potential has been shown to strongly affect the activities of Trichoderma , including mycelial growth (Magan & Whipps, ; Kredics et al , ; Hussain et al , ), spore germination (Magan, ; Hussain et al , ), enzymatic activity (Kredics et al , , ) and their saprophytic activity (Eastburn & Butler, ). Hyphal growth, spore production and germination and biological control activity of Trichoderma species are generally negatively impacted by low soil water potentials (Eastburn & Butler, ; Clarkson et al , ).…”

“…Hussain et al () reported that the germination rate of T. viride and Gliocladium virens ( Trichoderma virens ) was maximum at osmotic potentials of −0.12 to −1.1 MPa, with maximum growth seen over an osmotic potential range of −0.12 to 2.15 MPa. Decreasing osmotic potential (−0.25 to −2.8 MPa) resulted in a decrease in mycelial growth (radial growth) of both T. harzianum and T. viride (Magan & Whipps, ). Similarly, mycelial growth of a T. harzianum isolate was inhibited by decreasing osmotic potential, with the secretion of enzymes implicated to be involved in mycoparasitism inhibited at low osmotic potential (Kredics et al , ).…”