Liquid culture production of microsclerotia and submerged conidia by Trichoderma harzianum active against damping-off disease caused by Rhizoctonia solani

Abstract

Media and culturing protocols were identified that supported the formation of submerged conidia and microsclerotia (MS) by Trichoderma harzianum Rifai strain T-22 using liquid culture fermentation. Liquid media with a higher carbon concentration (36 g L(-1)) promoted MS formation at all C:N ratios tested. Hyphae aggregated to form MS after 2 d growth and after 7 d MS were fully melanized. This is the first report of MS formation by T. harzianum or any species of Trichoderma. Furthermore, submerged conidia formation was induced by liquid culture media, but yields, desiccation tolerance, and storage stability varied with C:N ratio and carbon rate. Air-dried MS granules (<4% moisture) retained excellent shelf life under cool and unrefrigerated storage conditions with no loss in conidial production. A low-cost complex nitrogen source based on cottonseed flour effectively supported high MS yields. Amending potting mix with dried MS formulations reduced or eliminated damping-off of melon seedlings caused by Rhizoctonia solani. Together, the results provide insights into the liquid culture production, stabilization process, and bioefficacy of the hitherto unreported MS of T. harzianum as a potential biofungicide for use in integrated management programs against soilborne diseases.

The entomopathogenic fungus Beauveria bassiana produces microsclerotia‐like pellets mediated by oxidative stress and peroxisome biogenesis

“…Many filamentous fungi with diverse ecological functions are known to produce sclerotia for survival and persistence in adverse environmental conditions (Harel et al ., ; Georgiou et al ., ). Microsclerotia are compact hyphal aggregates that are smaller than conventional sclerotia (50–600 μm) (Jackson and Schisler, ; Shearer and Jackson, ; Jaronski and Jackson, ; Kobori et al ., ) and were described in entomopathogenic fungi such as Metarhizium anisopliae (Jaronski and Jackson, ; Jackson and Jaronski, ), M. acridum , M. robertsii (Mascarin et al ., ), M. brunneum (Jackson and Jaronski, ), M. rileyi (Song et al ., ) and Lecanicillium lecanii (Wang et al ., ). In Beauveria bassiana (Hypocreales: Cordycipitaceae), one of the most explored entomopathogenic fungi in biological control programs worldwide (Mascarin and Jaronski, ), microsclerotia production was recently described by Villamizar and colleagues (), although the molecular and cellular mechanisms involved in microsclerotial differentiation processes are still unknown.…”

The high osmotic response and cell wall integrity pathways cooperate to regulate morphology, microsclerotia development, and virulence in Metarhizium rileyi

“…For biocontrol applications, MS have been induced in high concentrations in liquid culture. They can be used as mycoinsecticides to manage insect pests12, as antagonists of plant pathogenic fungi3, as bioherbicides for the management macrophytes4, or bionematicides against root knot nematodes5. MS are desiccation tolerant, with excellent storage stability, and have the potential to produce many infective conidia24.…”

New formulation and delivery method ofCryphonectria parasiticafor biological control of chestnut blight

“…; Kobori et al . ). We expected this lower viability, because, unlike the other biofungicides based on sporulating fungi, C. parasitica hypovirulent strain formulations consist mainly of mycelium known to be less resistant than spores to adverse conditions (Glare et al .…”