Abstract
The commercial use of the entomopathogenic fungiMetarhiziumspp. in biopesticides has gained more interest since the discovery that several species of this genus are able to colonize roots. In general, commercial products withMetarhiziumare formulated based on conidia for insect pest control. The process of mass production, harvesting, and formulation of infective conidia can be detrimental for conidial viability. Entomopathogenic fungi such asMetarhiziumspp. are able to produce high concentrations of resistant structures, known as microsclerotia, when grown in liquid media. Microsclerotia are desiccation tolerant, with excellent storage stability, and are capable of producing high quantities of infective conidia after rehydration. The aim of this study was to evaluate microsclerotia production by different isolates ofMetarhiziumspp. and determine the effect of microsclerotia coated onto maize seeds on plant growth in the presence of soil-borne pathogenFusarium graminearum. On average, ~1 × 105microsclerotia/mL were produced by selected isolates ofM. anisopliae(A1080 and F672) andMetarhizium robertsii(F447). Microsclerotia were formulated as granules with diatomaceous earth and used for seed coating, after which propagules produced around 5 × 106CFU/g of seeds. In the presence of the plant pathogen, maize plants grown from untreated seeds had the lowest growth, while plants treated with theMetarhiziummicrosclerotia had significantly greater growth than the control plants. Hyphae were observed growing on and in root tissues in all theMetarhiziumspp. treatments but not in samples from control plants.Metarhiziumhyphal penetration points' on roots were observed 1 month after sowing, indicating the fungi were colonizing roots as endophytes. The results obtained indicate that microsclerotia can be coated onto seeds, providing plant protection against soil plant pathogens and a method to establishMetarhiziumin the ecto- and endo-rhizosphere of maize roots, allowing the persistence of this biocontrol agent.
Highlights
The commercial use of entomopathogenic fungi such as Metarhizium (Metschnikoff) Sorokin, 1883 (Hypocreales: Clavicipitaceae) or Beauveria (Balsamo) Vuillemin, 1912 (Hypocreales: Clavicipitaceae) as “mycoinsecticides” or “biopesticides” is generally practiced using the inundative biocontrol approach, where the environment harboring the insect pest is treated with high concentrations of infective fungal propagules (Eilenberg et al, 2001; Jackson et al, 2010)
Biomass Production All the fungal isolates had produced their highest biomass by day 3 (89.7 ± 16.5 mg/mL) and 4 (87.1 ± 15.1 mg/mL) after inoculation followed by a subsequent steady weight decrease (F28/78 = 5.1; p < 0.01; Figure 1A)
The highest production of blastospores was by B. bassiana Bb21 and M. guizhouense Bk41, both with 9.1 × 108 blastopores/mL, while the lowest was found in T. harzianum F327 with 9.6 × 106 blastospores/mL (LSD5% = 0.557; Figure 1B)
Summary
The commercial use of entomopathogenic fungi such as Metarhizium (Metschnikoff) Sorokin, 1883 (Hypocreales: Clavicipitaceae) or Beauveria (Balsamo) Vuillemin, 1912 (Hypocreales: Clavicipitaceae) as “mycoinsecticides” or “biopesticides” is generally practiced using the inundative biocontrol approach, where the environment harboring the insect pest is treated with high concentrations of infective fungal propagules (Eilenberg et al, 2001; Jackson et al, 2010). The development of mycoinsecticides as conidiogenic granules is preferred since fresh conidia are produced in situ where the target plant pathogens or insect pests dwell (Jackson and Jaronski, 2012) Using this propagule alternative, conidia avoid all the necessary steps from mass-production up to application, which can damage these fungal reproductive structures. Biocontrol agents formulated as conidiogenic granules have some additional advantages such as protection from the harmful effects of UV radiation or from unfavorable conditions such as high temperatures and low humidity to which microorganisms can be exposed after foliar applications Another benefit is that in soil, moisture content and temperatures are generally within the optimal range for fungal survival and growth (Jackson and Jaronski, 2009)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
