Nonspecific Factors Involved in Attachment of Entomopathogenic Deuteromycetes to Host Insect Cuticle

Abstract

The attachment of the conidia of the insect-pathogenic fungi Nomuraea rileyi, Beauveria bassiana, and Metarrhizium anisopliae to insect cuticle was mediated by strong binding forces. The attachment was passive and nonspecific in that the conidia adhered readily to both host and nonhost cuticle preparations. The hydrophobicity of the conidial wall and the insect epicuticle appeared to mediate the adhesion process. Detergents, solvents, and high-molecular-weight proteins known to neutralize hydrophobicity reduced conidial binding when added to conidium-cuticle preparations. However, these chemicals did not remove the hydrophobic components from the epicuticle or from conidial preparations. The outer surface of the conidium consists of a resilient layer of well-organized fascicles of rodlets. Intact rodlets extracted from B. bassiana conidia bound to insect cuticle and exhibited the hydrophobicity expressed by intact conidia. Both electrostatic charges and various hemagglutinin activities were also present on the conidial surface. However, competitiveinhibition studies indicated that these forces played little, if any, role in the adhesion process.

Implication of a regulator of G protein signalling (BbRGS1) in conidiation and conidial thermotolerance of the insect pathogenic fungusBeauveria bassiana

“…Beauveria bassiana is an insect pathogenic fungus that produces asexually derived hydrophobic conidia (Boucias et al, 1988) that adhere to the insect cuticle, germinate and produce hyphae that penetrate the cuticle via mechanical pressure and cuticle degrading enzymes (St Leger, 1993). Because of its pathogenic properties, B. bassiana is employed as a biological control agent against insect pests.…”

Effect of surface material on electrostatic charging of houseflies (Musca domestica L)

“…The accumulation of electrical charge on the surface of insects has attracted the attention of investigators working on the mechanisms involved in pollinator/pollen interactions,1–5 the attachment of entomopathogens to the host cuticle,6 and the development of novel bioelectrostatic traps 7. An insect may acquire an electrostatic charge in a variety of ways including: (1) frictional charging during flight,4 (2) from a surface by contact and frictional charging (Fig 1),8, 9 (3) induction charging from an electrical field,10 (4) ionic transfer across the cuticle via dermal glands or pore channels11, 12 or (5) attachment of charged particles to the cuticle 10.…”

Surfactant effects on wettability of Penicillium frequentans formulations to improve brown rot biocontrol

“…5 Pf909 conidial adhesion could be due to hydrophobic interactions, similar to those described for Botrytis cinerea, 32 and fungal entomopathogenic deuteromycetes. 33 The conidial adhesion of Bipolaris sorokiniana, B. cinerea, Colletotrichum graminicola, and Uromyces viciae-fabae appeared to be selective to hydrophobic surfaces as no adhesion was observed to hydrophilic glass surfaces. 30,32,[34][35][36][37] The relationship between spore germination and surface wettability has been investigated in some other studies where it was shown that conidia of C. graminicola 38 or Phyllosticta ampelicida 39 seldom germinate with deficient contact with a hard surface, whereas spores of Colletotrichum lagenarium germinate independently of the contact with surfaces.…”