Social Control of the Ovarian Cycle and the Function of Estrous Synchrony

SYNOPSIS. The social signals among groups of females can eitherenhance or suppress ovariancyclicity. The ovarian cycle is notunitary, but is instead the integrated product of several differentcomponents which are each affected by social signals of differentmodalities. This interaction between female behavior and ovariancycle components has different manifestations in different species.Depending on its temporal context and the social and physicalenvironment, the same behavior/hormone interaction can takedifferent forms. In some contexts, these interactions can beadaptive for the individual. In others, they can generate astrong epiphenomenon or artifact that may not confer a directadaptive advantage itself, but still be necessary for otheraspects of the coordination between social behavior and reproduction.     

Distribution, prevalence and host associations of Hymenoptera parasitic on Calliphoridae occurring in flystrike in New Zealand

Abstract. Between 1920 and 1930, four species of parasitoid Hymenoptera (Tachinaephagus zealandicus, Alysia manducator, Nasonia vitripennis and Brachymeria ucalegon) were imported to New Zealand as an aid in the control of the blowflies causing myiasis in sheep (flystrike). Their long-term effects have never been investigated and the extent to which they were successful in establishing and enlarging their ranges has been given scant regard over the last 60 years. A long-term epidemiological study of flystrike in New Zealand between 1986 and 1996 obtained 4061 samples of blowfly larvae from flystruck sheep and carrion and overall 1.1% of these larval samples (most from the North Island) were found to be parasitized. Tachinaephagus zealandicus and A. manducator were present in field strikes, together with the endemic Aphaereta aotea recently found to be a parasite of calliphorids. The endemic species Phaenocarpa antipoda was found in association with carrion but not flystrike. Neither N.vitripennis nor B.ucalegon were isolated from larvae in field strikes, the former because it parasitizes only pupae and the latter may be extinct as it has not been sighted since its introduction in 1919.
It is concluded that if parasitoid wasps are able to locate and parasitize blowfly larvae on struck sheep, then their parasitism rate on more accessible larvae on carcases may be correspondingly greater. For this reason their scope for use in integrated management of flystrike could be increased by culturing and field release.     

Isolated Phosphate-Solubilizing Soil Bacteria Promotes In vitro Growth of Solanum tuberosum L.

The capacity of four bacterial strains isolated from productive soil potato fields to solubilize tricalcium phosphate on Pikovskaya agar or in a liquid medium was evaluated. A bacterial strain was selected to evaluate in vitro capacity of plant-growth promotion on Solanum tuberosum L. culture. Bacterial strain A3 showed the highest value of phosphate solubilization, reaching a 20 mm-diameter halo and a concentration of 350 mg/l on agar and in a liquid medium, respectively. Bacterial strain A3 was identified by 16S rDNA analysis as Bacillus pumilus with 98% identity; therefore, it is the first report for Bacillus pumilus as phosphate solubilizer. Plant-growth promotion assayed by in vitro culture of potato microplants showed that the addition of bacterial strain A3 increased root and stems length after 28 days. It significantly increased stem length by 79.3%, and duplicated the fresh weight of control microplants. In this paper, results reported regarding phosphorus solubilization and growth promotion under in vitro conditions represent a step forward in the use of innocuous bacterial strain biofertilizer on potato field cultures.Key words: Bacillus sp., phosphorus soluble, Pikovskaya agar, potato rhizosphere, plant growth promoting rhizobacteria     

Signalling between Pathogenic Rust Fungi and Resistant or Susceptible Host Plants

Rust fungi are obligately biotrophic plant parasites that obtaintheir nutrients from living host cells. The initiation of thetwo parasitic phases of these fungi generally requires topographicsignals from the plant surface followed, for the dikaryoticphase, by a successive sequence of signals to control furtherfungal development within the plant. During the fungal lifecycle, three types of intracellular structures (invasion hyphae,M-, and D-haustoria) are formed and each may differently affectthe host membrane that surrounds it, as well as affecting othercellular components. Each intracellular structure also preventsnon-specific plant defences triggered by fungal activities,possibly by interfering with the signalling system rather thandefence expression. In resistant host cultivars, cellular invasiontriggers a rapid cell death (the hypersensitive response) thatshares some features with developmentally programmed cell deathin animal and plant tissues, and is controlled by parasite-specificresistance genes that resemble those that defend plants againstother types of pathogens. Evidence from one system suggeststhat this response is specifically elicited by a fungal peptideand does not involve the oxidative burst typical of resistanceexpression in other plant-pathogen interactions. However, overall,few of the molecules involved in any of these plant-rust fungiinteractions have been completely characterized and much isleft to be discovered, particularly with respect to how cellularsusceptibility to rust fungi is conditioned.Copyright 1997 Annalsof Botany Company Apoptosis; biotrophy; elicitor; hypersensitive response; oxidative burst; suppressor; Uromyces vignae     

Studies in the physiology of the onion plant; further experiments on the effects of storage temperature and other factors on onions grown from sets

A wide range of factorial experiments at Wisley on onions grown from sets included combinations of the factors: storage of sets at high and low temperatures during the winter, variety, set size, set planting date and nitrogen manuring. Bolting, yield and ripening data are recorded. One experiment was repeated in Scotland and Northumberland where early ripening was expected to be more important than at Wisley. In general, all the factors enumerated except nitrogen manuring had large effects on bolting and yield, and storage temperature had a large effect on the time of ripening. Varieties can be selected such that large sets may be used without appreciable loss by bolting and maximum yield thus secured. Storage temperatures of from 20 to 24° C., applied for about 14 weeks from October onwards, can be used to control bolting and to increase the yield even of non-bolting strains by delaying ripening and so extending the growth period. Storage at 24° C. is more effective in preventing bolting than the lower temperatures, but 20° C. is probably more effective in delaying ripening. High-temperature storage is probably unsuitable for sets to be planted in the north and west of Great Britain because of the difficulty of ripening the bulbs. For these districts low-bolting strains are therefore essential. Storage at o° C. gives only a partial control of bolting and has no effect on ripening. Late planting of sets, although very effective in controlling bolting, results in a substantial loss of yield and, therefore, is not a practical measure. Nitrogen manuring had practically no effect on yield and could not be used to prevent the loss of yield caused by late planting.