Abstract
The European corn borer moth, (ECB), Ostrinia nubilalis (Lepidoptera: Crambidae, Pyraustinae) is one of the most destructive pests of maize worldwide. ECB has two pheromone-strains, separated by specific ratios of isomers of E- and Z11-tetradecenyl acetates (E11- and Z11-14Ac), but appearing morphologically identical. Accordingly, E- and Z-ECB pheromone traps are available for the respective populations for practical monitoring of the flight, however, traps for Z-strain are unreliable for practical usage in some parts of Central-Europe. E- and Z-ECB populations occur in sympatry in some areas, while in allelopatry in other areas. Determining the strains before the flight of adults, when difference in the composition of their respective pheromones is manifested, would be of practical interest for early warning. In addition to the known fatty-acyl-reductase (FAR) marker, further markers would allow more comprehensive studies. We screened the following common markers for mitochondrial and nuclear DNA regions: partial cytochrome c oxidase I (COI), cytochrome B (CytB), the second spacer of the internal transcribed spacer (ITS2), Elongation factor 1a (EF1a) and actin gene (Act). In addition, a marker of the Δ11-desaturase gene (11desat), linked to biosynthesis of female-produced sex pheromone, was also included, because we reported earlier a differential expression for this site. Three Z-ECB populations locating at distant sites within Hungary, an area where only Z-strain occurs, and an E-ECB population in Slovenia, known as the closest-occurring E-strain, were included into the study. Separate laboratory colonies were established from each population, and F1 generations were sampled to verify the identity of pheromone strains, by analysing the composition of sex pheromone by gas chromatography linked to an electroantennographic detector (GC-EAD). Molecular studies were conducted using specimens taken from the F2 generations. Results of genetic studies showed that there were no differences between the Z and E populations for the common markers. In contrast to this, several nucleic acid changes (11 nt in 4 positions) were found between the three Z-populations (Hungary) and the E-population (Slovenia) in the desaturase marker. Further study is required to reveal whether the differences found in this study are consistent across E-populations, thus making these markers suitable for diagnostic purposes.
Highlights
The European corn borer moth, (ECB), Ostrinia nubilalis (Lepidoptera: Crambidae, Pyraustinae) is one of the most destructive pests of maize worldwide
E- and Z-ECB pheromone traps are available for the respective populations for practical monitoring of the flight, traps for Z-strain are unreliable for practical usage in some parts of Central-Europe
Separate laboratory colonies were established from each population, and F1 generations were sampled to verify the identity of pheromone strains, by analysing the composition of sex pheromone by gas chromatography linked to an electroantennographic detector (GC-EAD)
Summary
The European corn borer moth, (ECB), Ostrinia nubilalis (Lepidoptera: Crambidae, Pyraustinae) is one of the most destructive pests of maize worldwide. More recent data were needed to track the actual appearance of respective strains for risk assessment in maize This is because strains are different in their preferences to secondary host plants, especially to some common weed species associated to maize field, which could be potential sources of re-infestations of maize (Schmitz, 1999; Pelozuelo et al, 2004). The search for pheromone strain-specific molecular markers revealed so-far only subtle differences, with the only notable exception being the sex-linked Tpi gene (Dopman et al, 2005). Even this difference in the Tpi gene needs care in practical exploitation, as there is 99% uniformity within the E-strain, the similarities within the Z-strain were found to be only 74%
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