Effects of genetic structure of Lupinus arboreus and previous herbivory on Platyprepia virginalis caterpillars

Two leaf-feeding caterpillars, western tussock moth (Orgyia vetusta) and ranchman's tiger moth (Platyprepia virginalis) are abundant on Lupinus arboreus along the California coast. Previous experiments and observations suggested that feeding caused by either of these two folivores could reduce the performance and possibly the abundance and distribution of the other species. Previous common garden experiments also indicated that genetically determined characteristics of the host plants were important for O. vetusta. Here we examined the effects of familial origin of the host plant, and previous damage caused by O. vetusta on the abundance of P. virginalis. Plants with parents from one of three locations had higher numbers of P. virginalis than plants with parents from the other two locations. However, this effect of plant origin depended on the statistical analysis and was not as strong as the effect of prior damage by O. vetusta on numbers of P. virginalis. Counter to our expectation, bushes that supported higher levels of damage by O. vetusta in the previous summer had more P. virginalis caterpillars. This strong effect could result by both moth species selecting bushes with the same traits or as the result of herbivory by O. vetusta enhancing the susceptibility of bushes for P. virginalis. Received: 28 October 1998 / Accepted: 14 March 1999     

Impact of melatonin and tryptophan on water stress tolerance in white lupine (Lupinus termis L.)

Melatonin  has been identified as a signal molecule that regulates plant responses to different abiotic and biotic stresses. Melatonin (MT) and its precursor tryptophan (Try) have a major role in improving plant stress tolerance to different environmental stresses such as water deficiency. The rapid increase in the Egyptian population caused insufficient protein sources, especially those of animal origin, in their diet. The possible solution is to augment the diet with legumes such as white lupine which are relatively rich in protein. Thus, the current experimental work was carried out to find changes in growth, biochemical aspects and yield quantity and quality of white lupine plant with spraying of both MT and Try at different concentrations on plant shoot under water deficit stress conditions. Results showed that water deficit (75 or 50% of water irrigation requirements; WIR) caused significant reduction in growth, photosynthetic pigments, indole acetic acid and yield compared with those received 100% WIR. Seed yield significantly decreased (p < 0.05) by 26.98 and 41.64% by decreasing WIR to 75 and 50%. The decrease was accompanied by significant increase in phenolic contents, hydrogen peroxide, lipid peroxidation and some antioxidant enzymes, while nitrate reductase enzyme was decreased. However, external application of either MT or Try significantly alleviated the adverse effects of water deficit (growth suppression), since MT or Try-treated plants recovered more quickly than untreated plants. Moreover, MT or Try—treated plants had higher photosynthetic pigments, indole acetic acid, phenolic, as well as yield quantity and quality under the three WIR as compared with untreated plants. Melatonin treatment at 100 µM and Tryptophan at 200 µM increased weight of seeds/plant by 78.29 and 52.19%, 71.49 and 43.78% and 41.21 and 13.07% in plants irrigated with 100, 75 and 50% WIR, respectively. Exogenous MT and Try significantly reduced hydrogen peroxide and malondialdehyde content, while markedly increased the activities of antioxidant enzymes and nitrate reductase under different WIR. Finally, the current study concluded that MT and Try treatments alleviated the detrimental effects of water deficiency and accelerated the recovery mainly via improving white lupine plants tolerance in forms of enhancing photosynthetic pigments, indole acetic acid, phenolic and antioxidant capacity.     

Effects of bark beetle pheromones on the attraction of Monochamus alternatus to pine volatiles

Abstract We evaluated the attraction of Monochamus alternatus Hope (Coleoptera: Cerambycidae), Dryocoetes luteus Blandford and Orthotomicus erosus Wollaston (Coleoptera: Curculionidae: Scolytinae) to multiple-funnel traps baited with the pine volatiles, ethanol and (+)-α-pinene and the bark beetle pheromones, ipsenol and ipsdienol. M. alternatus were attracted to traps baited with ethanol and (+)-α-pinene but not those baited with ipsdienol and ipsenol. Ipsdienol and ipsenol decreased catches of M. alternatus in traps baited with ethanol and (+)-α-pinene. Traps baited with either binary combinations of ethanol and (+)-α-pinene or ipsdienol and ipsenol were attractive to D. luteus and O. erosus. The addition of ipsenol and ipsdienol to traps baited with ethanol and (+)-α-pinene synergized attraction of O. erosus but not D. luteus.     

The sandfly Lutzomyia longipalpis shows specific humoral responses to bacterial challenge

Abstract The presence of immune molecules induced by microorganisms in the haemolymph of Lutzomyia longipalpis sandflies has been investigated. Injections of Escherichia coli and Micrococcus luteus into female sandflies induced anti-bacterial activity in the haemolymph. Inhibition zone assays showed that haemolymph from E.coli and M.luteus injected sandflies differentially inhibited M.luteus growth. This differential effect was specific to M. luteus infection since anti-Zs. coli activity was similar in haemolymph from both E.coli oxM.luteus injected sandflies. Haemolymph following injection of either bacteria showed the induction of a 4kDa peptide. Haemolymph from M.luteus injected sandflies also contained a 33 kDa polypeptide which was absent in haemolymph from E.coli and control uninfected insects. Sandflies, in common with other insects, were shown to possess general and specific humoral immune responses to the presence of microorganisms.