Molecular phylogeny of Diadegma species important in biological control of Plutella xylostella

摘要

Knowing the identity 01 a biological control agent and the pest host is essential lor any successtul biological control program. Accurate identification of the important natural enemies (e.g. Diadegma spp. (Ichneumonoidea: Ichneumonidae: Campopleginae), and Cotesia spp. ( Ichneumonoidea: Braconidae))attacking Plutella xylostella L. has traditionally been done using morphological characters. Reeentlymolecular studies of both parasitoids and hosts appeared in the literature.Most Diadegma species associated with P. xylostella can be differentiated with molecular biological techniques e. g. polymerase chain reaction-restriction fragment length polymorphism ( PCR-RFLP) and sequences of the mitochondrial (cytochrome oxidase I,COI) and ribosomal DNA (second internal transcribed spacer, ITS2).During the present study, sequences of Diadegma species of two different evolving genetic regions, the COI region and the ITS2, were examined and analysed phylogenetically with sequences of the Ichneumonoidea obtained from the database GenBank (May 2005). COI sequences (446 characters) of 47 different genera of both Braconidae and Ichneumonidae were found. Phylogenetic relationships between Braconidae and Ichneumonidae were investigated and revealed a monophyly of the Diadegma species, which clusteredtogether with other Ichneumonidae. The monophyly of Braconidae and Ichneumonidae recognized by morphological characters could not be confirmed.Additionally, ITS2 sequences of four genera of Braconidae and Ichneumonidae were obtained from GenBank ( May 2005) . Maximum parsimony analyses showed again a monophyly for the genus Diadegma.The use of the COI region and the ITS2 for the examination of higher-level phylogeny is discussed.