Typing Primus necrotic ringspot virus isolates by serology and restriction endonuclease analysis of PCR products

Primus necrotic ringspot virus (PNRSV) isolates were characterised by bioassays, serotyping and restriction fragment length polymorphism (RFLP) analysis of PCR products. Based on symptoms in host trees and bioassays it was concluded that only one of the 16 tested isolates is severe. The serotyping results demonstrated that by using four different MAbs in TAS-ELISA the tested isolates could be divided into four subgroups, however, the severe isolate could not be singled out. RFLP analysis of PCR products supported the serotyping data but did not differentiate between isolates of the two main serological subgroups. A restriction map, derived from sequence analysis of the PCR products obtained from selected isolates, allowed exact location of the restriction sites within the PCR products of each isolate. A mild isolate with a unique genome structure was identified by both serological and RFLP assays. As far as we are aware, this is the first report on sub-grouping of PNRSV isolates by bioassays, serotyping with MAbs and RFLP analysis.     

Differential response of Trichogramma wasps to extreme sex pheromone types of the noctuid moth Heliothis virescens

1. Chemical espionage in nature may occur when predators or parasitoids home in on animal or plant communication signals. Parasitoid wasps are known to use pheromones emitted by adults hosts to locate host eggs, larvae or pupae. The response of Trichogramma egg parasitoids to a synthetic sex pheromone blend of moths has been shown in a number of studies over the past 40 years. 2. Trichogramma pretiosum (Hymenoptera, Trichogrammatidae) is a tiny parasitic wasp, attacking the eggs of the noctuid moth Heliothis virescens (Lepidoptera, Noctuidae). This study investigated whether T. pretiosum homes in on the sex pheromone of H. virescens at close range. The arrestment response of the wasps to sex pheromone gland extracts of two types of female moths, so‐called high and low females, was also tested, referring to two selected extreme pheromone types of H. virescens. The study also investigated whether the wasps would mount females, possibly to hitchhike with them. 3. The wasps were arrested by the common, ‘low’ pheromone, but not by the rare, ‘high’ pheromone or by extracts from male hairpencils. The wasps did not show a preference for separate sex pheromone compounds, but when pre‐exposed to the major sex pheromone component of H. virescens before the tests together with H. virescens eggs, they did show a preference, indicating learning behaviour. In the mounting experiments, mated females were mounted significantly more than virgin females or males, suggesting that hitchhiking is a strategy used by these wasps to locate moth eggs. 4. This represents the first study to show a differential response of parasitoid wasps to two different sex pheromone types in a single host species. The results warrant further investigations into the potential role of parasitic wasps in the evolution of sexual communication in moths.     

A DNA test to sex most birds

Birds are difficult to sex. Nestlings rarely show sex-linked morphology and we estimate that adult females appear identical to males in over 50% of the world's bird species. This problem can hinder both evolutionary studies and human-assisted breeding of birds. DNA-based sex identification provides a solution. We describe a test based on two conserved CHD (chromo-helicase-DNA-binding) genes that are located on the avian sex chromosomes of all birds, with the possible exception of the ratites (ostriches, etc.; Struthioniformes). The CHD-W gene is located on the W chromosome; therefore it is unique to females. The other gene, CHD-Z, is found on the Z chromosome and therefore occurs in both sexes (female, ZW; male, ZZ). The test employs PCR with a single set of primers. It amplifies homologous sections of both genes and incorporates introns whose lengths usually differ. When examined on a gel there is a single CHD-Z band in males but females have a second, distinctive CHD-W band.     

The response of dodder {Cuscuta spp.) seedlings to phytohormones under various light regimes

Phytohormones were screened for their effects on induction of coiling and prehaustoria in de-etiolated excised dodder seedlings under different light treatments. Zeatin stimulated coiling and the formation of prehaustoria under all light tested, even in darkness. A synergistic effect was observed with zeatin and far-red light (700–800 nm) but not with red light (600–700 nm) on the formation of prehaustoria. Application of indole-3acetic acid inhibited zeatin-induced coiling and prehaustoria development under blue (400–500 nm) and a mixture of red plus far-red light, but not in blue plus far-red light. Ethylene had no effect on coiling and prehaustoria development. Observations suggest that zeatin-induced coiling and prehaustoria development may be mediated by phytochrome.