Specific ribosomal DNA marker for early polymerase chain reaction detection of Aphelinus hordei (Hymenoptera : Aphelinidae) and Aphidius colemani (Hymenoptera : Aphidiidae) from Diuraphis noxia (Homoptera : Aphididae)
Yc. Zhu et al., Specific ribosomal DNA marker for early polymerase chain reaction detection of Aphelinus hordei (Hymenoptera : Aphelinidae) and Aphidius colemani (Hymenoptera : Aphidiidae) from Diuraphis noxia (Homoptera : Aphididae), ANN ENT S A, 93(3), 2000, pp. 486-491
To monitor aphid parasitism by Aphelinus hordei (Kurdjumov) and Aphidius co
lemani Viereck, we developed specific ribosomal DNA markers to distinguish
them from several other cereal aphid parasitoid species and two important h
ost species, the Russian wheat aphid, Diuraphis noxia (Mordvilko), and the
greenbug, Schizaphis graminum (Rondani). Ribosomal DNA sequences for the in
ternal transcribed spacer 2 (ITS2) were first cloned and sequenced from A.
hordei, A. albipodus Hayat & Fatima, A. asychis Walker, A. varipes (Foerste
r), A. colemani, D. noxia, and S. graminum. We designed specific primers ba
sed on the ITS2 sequences. Polymerase chain reaction (PCR) amplification of
wasp and aphid DNA using these primers, followed by agarose gel electropho
resis, successfully distinguishes A. hordei and A. colemani from all three
other Aphelinus species and two aphid species. A 411-bp nucleotide fragment
and a 571-bp fragment were amplified only from A. hordei and from A. colem
ani, respectively, and no such fragments were amplified from any other wasp
species or aphids. DNA could be detected at a level as low as 10(-3) adult
wasp equivalent for A. hordei and 5 x 10(-4) adult wasp equivalent for A.
colemani. The DNA of both species was detectable in parasitized D. noxia 24
h after initial contact with adult parasitoid pairs.