Effects of Exogenous Nutrients on Conidial Germination and Virulence against the Silverleaf Whitefly for Two Hyphomycetes

James, Rosalind R.

doi:10.1006/jipa.2000.5001

Cited by 32 publications

(22 citation statements)

References 23 publications

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“…The mortality response that occurred after exposure to different dosages of the fungi was lower than previously reported by us (James, 2001;James and Jaronski, 2000) and by Wraight et al (1998), despite similar test conditions. Due to the low mortality, we were not able to accurately estimate LC 50 levels in the probit analysis because our highest dosages only caused mean mortality levels that were around 50-70%.…”

Section: Discussioncontrasting

confidence: 77%

“…These fungi are easily cultured in vitro, and thus lend themselves for use as microbial pesticides for several arthropod pests, including the silverleaf whitefly, Bemisia argentifolii (Faria and Wraight, 2001). If B. bassiana conidia are germinated prior to being applied to whitefly nymphs, the infection rate is higher than when ungerminated conidia are used (James, 2001). One possible explanation for this result is that the cuticle is unfavorable to spore germination, by either lacking the proper stimuli for, or by directly reducing or inhibiting germination.…”

Section: Introductionmentioning

confidence: 99%

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Cuticular lipids and silverleaf whitefly stage affect conidial germination of Beauveria bassiana and Paecilomyces fumosoroseus

James

Buckner

Freeman

2003

Journal of Invertebrate Pathology

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Section: Discussioncontrasting

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Cuticular lipids and silverleaf whitefly stage affect conidial germination of Beauveria bassiana and Paecilomyces fumosoroseus

James

Buckner

Freeman

2003

Journal of Invertebrate Pathology

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“…Here we found that Bbhog1 was an important virulence determinant of B. bassiana and influenced at least three aspects of infection, spore viability, adherence to the insect cuticle, and appressorium formation. The rate of conidial germination is an important indicator of virulence in entomopathogenic fungi and is to some degree correlated with virulence (2,26,43,46). It was demonstrated previously that physical manipulation of growth conditions can significantly modify the endogenous compounds synthesized and channeled into the propagules of fungi (33,38).…”

Section: Discussionmentioning

confidence: 99%

Mitogen-Activated Protein Kinase hog1 in the Entomopathogenic FungusBeauveria bassianaRegulates Environmental Stress Responses and Virulence to Insects

Zhang

Zhao

Fang

et al. 2009

Appl Environ Microbiol

153

101

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Beauveria bassiana is an economically important insect-pathogenic fungus which is widely used as a biocontrol agent to control a variety of insect pests. However, its insecticide efficacy in the field is often influenced by adverse environmental factors. Thus, understanding the genetic regulatory processes involved in the response to environmental stress would facilitate engineering and production of a more efficient biocontrol agent. Here, a mitogen-activated protein kinase (MAPK)-encoding gene, Bbhog1, was isolated from B. bassiana and shown to encode a functional homolog of yeast HIGH-OSMOLARITY GLYCEROL 1 (HOG1). A Bbhog1 null mutation was generated in B. bassiana by targeted gene replacement, and the resulting mutants were more sensitive to hyperosmotic stress, high temperature, and oxidative stress than the wild-type controls. These results demonstrate the conserved function of HOG1 MAPKs in the regulation of abiotic stress responses. Interestingly, ⌬Bbhog1 mutants exhibited greatly reduced pathogenicity, most likely due to a decrease in spore viability, a reduced ability to attach to insect cuticle, and a reduction in appressorium formation. The transcript levels of two hydrophobin-encoding genes, hyd1 and hyd2, were dramatically decreased in a ⌬Bbhog1 mutant, suggesting that Bbhog1 may regulate the expression of the gene associated with hydrophobicity or adherence.Mycoinsecticides are important insect pest control agents (10,19,41). Unlike entomopathogenic bacteria and viruses that invade insects through their digestive tracks, fungal pathogens penetrate the host integument and are considered the only group of microbial biocontrol agents active against sucking-type insect pests (21, 49). However, low killing speed and sensitivity to adverse environment factors such as desiccation, high temperature, and UV radiation limit the widespread use of entomopathogenic fungi (6,22,40). Thus, an understanding of the regulatory processes involved in response to environment stress is essential for commercial development and improvement of these biocontrol fungi.Mitogen-activated protein kinases (MAPKs), a family of serine-threonine protein kinases, are widespread in eukaryotic cells and play crucial roles in transduction of a variety of extracellular signals and regulation of various development and differentiation processes (37, 45). MAPKs are usually activated by MAPK kinases, which are in turn activated by MAPK kinase kinases. These MAPK kinase kinase-MAPK kinase-MAPK cascades are conserved in eukaryotic cells and have been studied extensively in many organisms (45). In Saccharomyces cerevisiae, at least five MAPK pathways have been identified. These pathways are designated the FUS3, KSS1, HOG1, SLT2, and SMK1 MAPK cascades, and they are involved in mating, filamentous growth, the high-osmolarity response, cell integrity, and ascospore formation, respectively (20). Recent studies showed that homologs of HOG1 are involved in responses to osmotic stress (12,29,44,58), oxidative stress (28, 47), heat shock (28), and ...

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“…Because of its potential to cause epizootics naturally, P. fumosoroseus is used for microbial control of insect pests (Jackson et al, 1997). Conidia are often the means for dispersal and transmission of entomopathogenic fungi; they must come into contact with, germinate on, and then penetrate the insect cuticle (James, 2001). However, there is very limited information about conidiation in P. fumosoroseus.…”

Section: Introductionmentioning

confidence: 99%

Light-regulated asexual reproduction in Paecilomyces fumosoroseus

et al. 2004

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The entomopathogenic fungus Paecilomyces fumosoroseus has been successfully used in the control of several insect pests. Asexually produced spores (conidia) are the means for dispersal and transmission of the entomopathogen; upon contact with the insect cuticle they germinate and penetrate the host. In model fungal systems it has been found that phototropism, resetting of the circadian rhythm, the induction of carotenogenesis and the development of reproductive structures are controlled by blue light. The effect of light quality on conidial yield of P. fumosoroseus was investigated. Incubation in total darkness resulted in continued vegetative growth and lack of reproductive structures. In contrast, growth of the fungus in continuous illumination or under a night-day regime resulted in prolific formation of conidiophores bearing abundant mature conidia. Conidiation was photoinduced in competent mycelia by a single pulse of blue light and colonies were competent only after they had grown at least 72 h under total darkness. The fluence-response curves generated with blue light indicated that the minimal fluence required for the photomorphogenetic response was 180 mmol m "2 and the half-maximal response was at 400 mmol m "2. A fluence of 540 mmol m "2 was enough to saturate the system, inducing the maximum production of 2?12610 8 conidia per colony.Higher light intensities markedly decreased conidiation, suggesting the occurrence of a process of adaptation. The authors propose the existence of a dual light-perception system with at least two photoreceptors in P. fumosoroseus, one promoting and one inhibiting conidiation.

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Effects of Exogenous Nutrients on Conidial Germination and Virulence against the Silverleaf Whitefly for Two Hyphomycetes

Cited by 32 publications

References 23 publications

Cuticular lipids and silverleaf whitefly stage affect conidial germination of Beauveria bassiana and Paecilomyces fumosoroseus

Cuticular lipids and silverleaf whitefly stage affect conidial germination of Beauveria bassiana and Paecilomyces fumosoroseus

Mitogen-Activated Protein Kinase hog1 in the Entomopathogenic FungusBeauveria bassianaRegulates Environmental Stress Responses and Virulence to Insects

Light-regulated asexual reproduction in Paecilomyces fumosoroseus

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