The theory of plant-insect coevolution provides for diffuse coevolution and the expectation that plants evolve broad-spectrum chemical defenses with which some insects coevolve by detoxifying and using the compounds as host-location cues. Specific biochemical modes of action have been assigned to relatively few such defense chemicals and one major class, the terpenoids, is investigated here. Six terpenoids inhibited the enzyme acetylcholinesterase (derived from electric eel) and elicited the appropriate in vivo effects of insect paralysis and mortality. The diterpene gossypol was a reversible uncompetitive inhibitor. Five monoterpenes, representing a range of functional groups, were reversible competitive inhibitors apparently occupying at least the hydrophobic site of the enzyme's active center. Such data suggest the involvement of acetylcholinesterase in the coevolved insect response to terpenoids.

No abstract

Interspecific populations derived from crossing cultivated field pea, Pisum sativum, with the wild pea relative, Pisum fulvum, were scored for pod and seed injury caused by the pea weevil, Bruchus pisorum. Pod resistance was quantitatively inherited in the F2 population, with evidence of transgressive segregation. Heritability of pod resistance between F2 and F3 generations was very low, suggesting that this trait would be difficult to transfer in a breeding program. Seed resistance was determined for the F2 population by testing F3 seed tissues of individual F2 plants and pooling data from seed reaction for each F2 plant (inferred F2 genotype). Segregation for seed resistance in the F2 population of the cross Pennant/ATC113 showed a trigenic mode of inheritance, with additive effects and dominant epistasis towards susceptibility. Seed resistance was conserved over consecutive generations (F2 to F5) and successfully transferred to a new population by backcross introgression. Seed resistance in the backcross introgressed population segregated in a 63 : 1 ratio, supporting the three-gene inheritance model. It is proposed that complete resistance to pea weevil is controlled by three major recessive alleles assigned pwr1, pwr2, and pwr3, and complete susceptibility by three major dominant alleles assigned PWR1, PWR2, and PWR3. It is recommended that large populations (>300 F2 plants) would be required to effectively transfer these recessive alleles to current field pea cultivars through hybridisation and repeated backcrossing.

No abstract

Tandem evaluation of ionic liquids and imidazolium salts toxicity and performance in dye sensitised solar cells is presented.

Narrow linewidth emission features observed in the near-UV following y 6 P state excitation of atomic manganese isolated in the solid rare gases are assigned to b 4 D and a 4 P states. These states arise from the 3d 5 4s 2 electronic configuration, identical to that of the 6 S ground state, and the origin of the narrow linewidths. Two thermally stable sites, labeled blue and red on the basis of their position in absorption spectra, are occupied by atomic Mn in Ar and Kr while a single site is present in Xe. The red site produces a single, narrow line emission for the b 4 D state at 329 nm. In contrast, a lineshape analysis of the complex blue site b 4 D state emission between 331 and 332 nm reveals the occurrence of three zero phonon lines ͑ZPLs͒. Millisecond emission decay curves recorded for these features are found to be complex, requiring double and triple exponential fit functions. The origins of the complex decays and multiple ZPLs are shown to arise from weak crystal field splitting ͑CFS͒ of the J = 7 / 2 spin-orbit level of the b 4 D state of atomic Mn isolated in the blue site of the solid rare gases. Fields of cubic symmetry are capable of inducing splitting for J Ͼ 3 / 2 so atoms isolated in both single vacancy and tetravacancy sites in the fcc lattices of the solid rare gases are prone to this effect. b 4 D state emission is also produced following y 6 P excitation for Mn atoms occupying the red sites in Ar and Kr. However, Mn atoms isolated in the larger tetravacancy sites have small matrix shifts and do not exhibit any CFS. The magnitudes of the weak CF splittings are shown to depend on both the excited state electronic configurations 3d 5 4s 2 b 4 D and 3d 6 4s 1 a 4 D states and the size of the matrix site occupied by atomic Mn.

The pea weevil, Bruchus pisorum, is one of the most intractable pest problems of cultivated field pea (Pisum sativum) in the world. Pesticide application, either as a contact insecticide spray to the field pea crop or fumigation of the harvested seed, is the only available method for its control. The aim of the study was to develop a quick and reliable method to screen for pea weevil resistance and increase efficiency in breeding for this important trait. Backcrossed progenies derived from an interspecific cross between cultivated field pea and its wild relative (Pisum fulvum, source of resistance for pea weevil) were subjected to natural infestation in field plots. Mature seeds were hand-harvested, stored to allow development of adult beetles, and then separated into infested and non-infested using a density separation method in 30% caesium chloride (CsCl). Susceptibility and resistance of the progenies were calculated based on this method and further confirmed by a glasshouse bioassay. Resistance in backcross populations improved considerably through selection of resistant lines using the density separation method. We found that the method using CsCl separation is a useful tool in breeding for pea weevil resistance. We were able to introgress pea weevil resistance from P. fulvum into cultivated field pea through backcrossing to produce several advanced pea weevil resistant lines following this procedure.

No abstract