Impact of culture age on conidial germination, desiccation and UV tolerance of entomopathogenic fungi

Cliquet, Sophie

doi:10.1080/09583157.2013.802289

Cited by 14 publications

(12 citation statements)

References 25 publications

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“…An unfortunate consequence of such reports is that it establishes unrealistic expectations regarding the performance of these agents in the field. Variations in temperature, humidity, and exposure to UV-irradiation are amongst some of the important abiotic factors that can significantly impact the efficacy of entomopathogenic fungi in field applications (Fernandes et al 2007;Le Grand and Cliquet 2013;Rangel et al 2005;Thompson et al 2006). Spore viability and persistence are also important considerations with some recent advances in our understanding of at least one molecular determinant involved, i.e., a putative fungal methyltransferase, reported by Qin et al (2014).…”

Section: Major Obstacles and Non-engineering Approachesmentioning

confidence: 98%

Improving mycoinsecticides for insect biological control

Ortiz‐Urquiza

Luo

Keyhani

2014

Appl Microbiol Biotechnol

140

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The desire for decreased reliance on chemical pesticides continues to fuel interest in alternative means for pest control including the use of naturally occurring microbial insect pathogens. Insects, as vectors of disease causing agents or as agricultural pests, are responsible for millions of deaths and significant economic losses worldwide, placing stresses on productivity (GDP) and human health and welfare. In addition, alterations in climate change are likely to affect insect ranges, expanding their access to previously constrained geographic areas, a potentially worrisome outcome. Metarhizium anisopliae and Beauveria bassiana, two cosmopolitan fungal pathogens of insects found in almost all ecosystems, are the most commonly applied mycoinsecticides for a variety of insect control purposes. The availability of the complete genomes for both organisms coupled to robust technologies for their transformation has led to several advances in engineering these fungi for greater efficacy and/or utility in pest control applications. Here, we will provide an overview of the fungal-insect and fungal-plant interactions that occur and highlight recent advances in the genetic engineering of these fungi. The latter work has resulted in the development of strains displaying (1) increased resistance to abiotic stress, (2) increased cuticular targeting and degradation, (3) increased virulence via expression of insecticidal protein/peptide toxins, (4) the ability to block transmission of disease causing agents, and (5) the ability to target specific insect hosts, decrease host fecundity, and/or alter insect behaviors.

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Section: Major Obstacles and Non-engineering Approachesmentioning

confidence: 98%

Improving mycoinsecticides for insect biological control

Ortiz‐Urquiza

Luo

Keyhani

2014

Appl Microbiol Biotechnol

140

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“…Water suspension, 1-h exposure (920 mW m −2 ), culturability (CFU) ~100 % Water suspension, 1-h exposure (1200 mW m −2 ), culturability (CFU) ~85 % Water suspension, 1-h exposure (1200 mW m −2 ), relative percent germination, 24-h incubation = 95 %, 48-h incubation = 100 % Water suspension, 4-h exposure (920 mW m −2 ), culturability (CFU) ~30 % Water suspension, 4-h exposure (1200 mW m −2 ), culturability (CFU) <5 % Water suspension, 4-h exposure (1200 mW m −2 ), relative percent germination, 24-h incubation = 28 %, 48-h incubation = 63 % ARSEF 2575, Metarhizium robertsii (Braga et al 2001c) Water suspension, 2-h exposure (full-spectrum sunlight), culturability (CFU) ~75 % Water suspension, 2-h exposure (UV-A sunlight), culturability (CFU) ~100 % Water suspension, 2-h exposure (full-spectrum sunlight), relative percent germination, 12-h incubation ~70 %, 24-h incubation ~100 % Water suspension, 2-h exposure (UV-A sunlight), relative percent germination, 12-h incubation ~95 %, 24-h incubation ~100 % Water suspension, 4-h exposure (full-spectrum sunlight), culturability (CFU) ~0 % Water suspension, 4-h exposure (UV-A sunlight), culturability (CFU) ~30 % Water suspension, 4-h exposure (full-spectrum sunlight), relative percent germination, 12-h incubation ~10 %, 24 h incubation ~10 % Water suspension, 4-h exposure (UV-A sunlight), relative percent germination, 12-h incubation ~25 %, 24-h incubation ~60 % were more sensitive to UV radiation than conidia from isolates cultured for 7 d (Le Grand and Cliquet 2013). Conidia from older cultures of M. acridum were also more tolerant to UV than conidia from the younger ones (Moore et al 1993) (see Table 1).…”

Section: Conditions Influencing the Tolerance Of Entomopathogenic Funmentioning

confidence: 99%

Tolerance of entomopathogenic fungi to ultraviolet radiation: a review on screening of strains and their formulation

et al. 2015

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Ultraviolet radiation from sunlight is probably the most detrimental environmental factor affecting the viability of entomopathogenic fungi applied to solar-exposed sites (e.g., leaves) for pest control. Most entomopathogenic fungi are sensitive to UV radiation, but there is great inter- and intraspecies variability in susceptibility to UV. This variability may reflect natural adaptations of isolates to their different environmental conditions. Selecting strains with outstanding natural tolerance to UV is considered as an important step to identify promising biological control agents. However, reports on tolerance among the isolates used to date must be analyzed carefully due to considerable variations in the methods used to garner the data. The current review presents tables listing many studies in which different methods were applied to check natural and enhanced tolerance to UV stress of numerous entomopathogenic fungi, including several well-known isolates of these fungi. The assessment of UV tolerance is usually conducted with conidia using dose-response methods, wherein the UV dose is calculated simply by multiplying the total irradiance by the period (time) of exposure. Although irradiation from lamps seldom presents an environmentally realistic spectral distribution, laboratory tests circumvent the uncontrollable circumstances associated with field assays. Most attempts to increase field persistence of microbial agents have included formulating conidia with UV protectants; however, in many cases, field efficacy of formulated fungi is still not fully adequate for dependable pest control.

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“…In fact, air‐dried conidia of Beauveria bassiana s.l. were more tolerant to UV‐B than fresh conidia (Le Grand and Cliquet ). In the current study, germination of conidia on SDAY was completely inhibited at doses ≥8·3 kJ m −2 .…”

Section: Discussionmentioning

confidence: 94%