Résumé
Abstract Nasonovia ribisnigri is a key pest of lettuce (Lactuca sativa L.) in Brazil that requires alternative control methods to synthetic pesticides. We report, for the first time, the occurrence of Paecilomyces niveus as an entomopathogen of the aphid Nasonovia ribisnigri in Pinhais, Paraná, Brazil. Samples of mummified aphids were collected from lettuce crops. The fungus P. niveus (PaePR) was isolated from the insect bodies and identified by macro and micromorphology. The species was confirmed by sequencing Internal Transcribed Spacer (ITS) rDNA. We obtained a sequence of 528 bp (accession number HQ441751), which aligned with Byssochlamys nivea strains (100% identities). In a bioassay, 120 h after inoculation of N. ribisnigri with pathogenic P. niveus had an average mortality of 74%. The presence of P. niveus as a natural pathogen of N. ribisnigri in Brazil suggests that it may be possible to employ P. niveus to minimize the use of chemical insecticides.
Resumo Nasonovia ribisnigri é uma praga-chave do cultivo de alface (Lactuca sativa L.), exigindo métodos alternativos ao controle químico. Este trabalho registrou pela primeira vez, a ocorrência de Paecilomyces niveus como agente entomopatogenico do afídeo N. ribisnigri em Pinhais, Paraná, Brasil. Amostras de afídeos mumificados foram coletadas em plantas de alface. O fungo P. niveus (PaePR) foi isolado do corpo dos insetos e identificado por macro e micromorfologia e, confirmado por sequenciamento da região ITS do DNA ribossomal. A sequencia parcial de 528 bp (número de acesso HQ441751) apresentou alinhamento com 100% de identidade com sequencias de raças de Byssochlamys nivea. No bioensaio de patogenicidade P. niveus apresentou uma mortalidade média de N. ribisnigri de 74% até 120 horas da inoculação. O registro da presença de P. niveus como um patógeno natural de N. ribisnigri no Brasil sugere o potencial de utilização para minimizar o uso de inseticidas.
Sujets)
Animaux , Aphides/microbiologie , Paecilomyces/physiologie , Aphides/croissance et développement , Brésil , Byssochlamys/classification , Byssochlamys/isolement et purification , Byssochlamys/physiologie , ADN fongique , Données de séquences moléculaires , Nymphe/croissance et développement , Nymphe/microbiologie , Paecilomyces/classification , Paecilomyces/isolement et purification , Analyse de séquence d'ADNRésumé
A phylogenetic analysis of the 5.8S rDNA and internal transcribed spacer (ITS1 and ITS2) sequences from some entomogenous Paecilomyces species supports the polyphyly of the genus and showed the existence of cryptic species. In the Eurotiales, anamorphs Paecilomyces variotii and Paecilomyces leycettanus were related to the teleomorphs Talaromyces and Thermoascus. In the Hypocreales, three major ITS subgroups were found, one of which included Paecilomyces viridis, Paecilomyces penicillatus, Paecilomyces carneus and isolates identified as Paecilomyces lilacinus and Paecilomyces marquandii. However, the majority of the P. lilacinus and P. marquandii isolates formed a distinct and distantly related subgroup, while the other major subgroup contained Paecilomyces farinosus, Paecilomyces amoeneroseus, Paecilomyces fumosoroseus and Paecilomyces tenuipes.