title: Virulence testing and extracellular subtilisin-like (Pr1) and trypsin-like (Pr2) activity during propagule production of Paecilomyces fumosoroseus isolates from whiteflies (Homoptera: Aleyrodidae).
abstract: To properly characterize several isolates of Paecilomyces fumosoroseus, a fungal entomopathogen of whiteflies (Homoptera: Aleyrodidae) and other insect pests for biocontrol purposes, virulence towards Trialeurodes vaporariorum, and subtilisin-like (Pr1) and trypsin-like (Pr2) protease activity during propagule production were investigated in monospore cultures (MCs). The virulence of three MCs towards second instar whiteflies was measured and expressed as lethal median concentration (LC50). Number and widthlength ratio of propagules (blastospores, hyphal bodies, short hyphae, submerged conidia) and extracellular proteolytic activity was determined simultaneously in liquid medium. Total protease activity was assayed with azocasein, Pr1 and Pr2 activity was determined with the substrates N-Succinyl-Ala-Ala-Pro-Phe-p-nitroanilide and N-Benzoyl-Phe-Val-Arg-pnitroanilide, respectively. Natural variability in virulence, propagule production and cuticle-degrading proteases among isolates was observed. Bioassays showed a LC50 of 1.1 x 1,000, 2.5 x 10,000 and 7.6 x 10,000 conidia/ml for MCs EH-506/3, EH-503/3 and EH-520/3, respectively, EH-506/3 being the most virulent isolate. Isolate EH-503/3 produced the highest yield of propagules (7.7 x 10000000 propagules/ml), followed by EH-520/3 with 6.4 x 10000000 and EH-506/3 with 1.0 x 10000000 propagules/ml. Subtilisin-like (Pr1) and trypsin-like (Pr2) activity was present in the three MCs. Subtilisin-like (Pr1) activity was highest (745.7 UPr1/ml at 120 h) in the most virulent isolate, EH-506/3, pointing at Pr1 as a phenotypic marker of virulence for P. fumosoroseus. EH-506/3 appears to be a good candidate for whitefly biocontrol due to its high virulence, Pr1 concentration and rapid transition to blastospores in submerged liquid medium.
authors.affiliation: Departamento el Hombre y su Ambiente, Universidad Autónoma Metropolitana-Xochimilco, México DF, México.
authors.forename: Judith
authors.initials: J
authors.lastname: Castellanos-Moguel
authors.forename: Margarita
authors.initials: M
authors.lastname: González-Barajas
authors.forename: Teresa
authors.initials: T
authors.lastname: Mier
authors.forename: María Del Rocío
authors.initials: Mdel R
authors.lastname: Reyes-Montes
authors.forename: Eduardo
authors.initials: E
authors.lastname: Aranda
authors.forename: Conchita
authors.initials: C
authors.lastname: Toriello
mesh_terms: D000818:Animals; D002863:Chromogenic Compounds; D045604:Extracellular Fluid / Q000201:enzymology; D005656:Fungal Proteins / Q000032:analysis*; D006430:Hemiptera / Q000382:microbiology*; D009842:Oligopeptides / Q000378:metabolism; D010143:Paecilomyces / Q000201:enzymology / Q000302:isolation & purification / Q000472:pathogenicity* / Q000502:physiology; D010572:Pest Control, Biological; D012100:Reproduction, Asexual; D012697:Serine Endopeptidases / Q000032:analysis*; D013379:Substrate Specificity; D014774:Virulence
chemical_list: D002863:Chromogenic Compounds; D005656:Fungal Proteins; D009842:Oligopeptides; D012697:Serine Endopeptidases