The effect of heat treatment and meristem-tip culture on June Yellows in strawberry

Because there is some evidence that June Yellows (JY) of strawberry may be caused by a pathogenic agent, combinations of heat treatment and meristem-tip culture that are known to eliminate some viruses from tissues were used in attempts to cure affected Cambridge Favourite strawberry plants from JY. None of 397 propagants derived from JY-affected plants subjected to various combinations of these treatments were freed from JY. Indeed, all propagants showed more obvious JY symptoms than the parent plants from which they were derived, suggesting that such treatments may be useful for detecting incipient JY in symptomless strawberry stocks.     

Ultrastructural changes associated with June Yellows in strawberry and with leaf yellowing symptoms of viral and genetic origin in Fragaria, Rubus and Ribes

Light and electron microscopy was used to study the ultrastructural effects of June Yellows (JY) in leaves of strawberry. Four cultivars of strawberry, affected to different extents by JY, were compared with healthy (JY-free) cv. Cambridge Favourite and with strawberry infected with strawberry crinkle rhabdovirus, Fragaria vesca infected with strawberry mottle virus (SMotV), raspberry and black currant showing virus-induced yellowing and with strawberry and raspberry showing chaemeric yellow sectors in the leaves. Except for isometric virus-like particles detected in SMotV-infected F. vesca, no virus-like particles or structures of other pathogenic agents were found in any of the tissues examined. Leaf cells of JY-affected strawberry showed severe disruption of chloroplasts and plasmalemma, whorls of membranous vesicles and decreased vacuole size. The extent and severity of these abnormalities increased with increased severity of JY symptoms but, even in leaves with mild JY symptoms, chloroplast abnormalities were obvious. In the most severely affected leaves, the cells lacked discrete vacuoles and extensive hypertrophy was seen in other organelles such as nuclei and mitochondria. Few, if any, ultrastructural abnormalities were observed in virus-infected strawberry or F. vesca, or in chaemeric leaves of strawberry and raspberry. By contrast, in raspberry and black currant with yellowed leaves caused by virus infection, the cells showed enlarged chloroplasts, decreased vacuole size and vesicle formation. However, chloroplast enlargement and disruption in this material seemed due to increased size of starch grains which were largely absent from swollen chloroplasts of JY-affected strawberry. The ultrastructural abnormalities observed in JY-affected strawberry are, therefore, not inconsistent with the possibility that a pathogenic agent may be involved in the condition.     

Silurian brachiopods in a stromatoporoid bioherm

Ludlovian limestone at Ljugarn, Gotland. repreqents a shallow marine environment of stromatoporoid biohenns and flanking areas of mud and stromatoporoid debris. Brachiopods were restricted to surfaces of the debris deposits. Lissatrypa sulcata, a smooth atrypacean, dominated the brachiopod fauna, with individuals living beak downward in high density clusters, developing weaker pedicle attachment and a sulcus during ontogeny. Surrounding low density areas of Lissatrypa included small, pedicleattached, non-sulcate shells. Howellella, Spirigerina, and Morinorhynchus? lived in isolated clusters near low density Lissatrypa populations, and 10 other very rare brachiopod species may have been non-reproducing members of the community. Brachiopcd species diversity, and thus number of niches, was lower in the biohermal enviroment than in bathymetrically equivalent, level-bottom communities.     

Do dung beetle larvae need microbial symbionts from their parents to feed on dung?

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An analysis of nucleotide and amino acid variability in the barcode region of cytochrome c oxidase I (cox1) in fishes

The 655 bp cytochrome c oxidase subunit I barcode region of single specimens of 388 species of fishes (four Holocephali, 61 Elasmobranchii and 323 Actinopterygii) was examined. All but two (Urolophus cruciatus and Urolophus sufflavus) showed different cox1 nucleotide sequences (99.5% species discrimination); the two that could not be resolved are suspected to hybridize. Most of the power of cox1 nucleotide sequence analysis for species identification comes from the degenerate nature of the genetic code and the highly variable nature of the third codon position of amino acids. Variation at the third codon position is bimodally distributed, and the more variable mode is dominated by amino acids with four or six codons, while the less variable mode is dominated by amino acids with two codons. The ratio of nonsynonymous to synomymous changes is much less than one, indicating that this gene is subject to strong purifying selection. Consequently, cox1 amino acid sequence diversity is much less than nucleotide sequence diversity and has very poor species resolution power. Fourteen of the 16 amino acid residues recognized as having important functions in the region of cox1 sequenced were completely conserved over all 388 species (and the bovine cox1 sequence), with one fish species varying at one of these sites, and three fish at another site. No significant differences in amino acid conservation were observed between residues in helices, strands and turns. Patterns of nucleotide and amino acid variability were very similar between elasmobranchs and actinopterygians.     

Food Aversion Plus Odor Cue Protects Crop From Wild Mammals

Abstract: Wild mammals cause foraging damage to crops worldwide and nonlethal methods are required for controlling such damage. Many wildlife management situations demand protection of untreated foods. We tested learned food aversion plus an odor cue as a paradigm for protecting untreated model crop items from European badgers (Meles meles). Following conditioning with a combination of ziram and clove oil, badgers avoided untreated maize cobs in presence of a clove odor cue. A clove oil control did not condition badgers. This work has been an important step before proceeding to full-scale field trials for protecting growing crops on a wider scale. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):785–791; 2008)     

Pre-selection for Phytophthora cactorum (Leb. &Cohn) Sehroet. resistance in apple seedlings

Inoculation of apple seedlings at the two-leaf stage with a Phytophthora cactorum zoospore suspension provided a rapid method of pre-selecting for collar rot resistance, since the susceptible plants died within 2 weeks of inoculation while the resistant plants continued to grow satisfactorily. The presence of the resistance gene Pc was not alone sufficient to explain the observed segregation.     

The influence of leaf litter on zooplankton in floodplain wetlands: changes resulting from river regulation

1. The loss of input of leaf litter through clearing of riparian vegetation may result in significant changes to aquatic ecosystems. River red gums (Eucalyptus camaldulensis) surrounding floodplain wetlands in the Murray–Darling Basin, Australia, contribute large quantities of leaf litter, but the quality of this resource may change depending on the timing of inundation. 2. We used experimental mesocosms to test the hypotheses that zooplankton would have a greater abundance with an input of leaf litter and that fewer zooplankton would emerge from egg banks in cleared than forested wetlands. The experiment was carried out in summer/autumn and in spring to test a third hypothesis that zooplankton would respond to changes in the timing of wetland inundation as a result of river regulation. 3. In summer/autumn, leaf litter reduced zooplankton abundance by 89% at the beginning of the experiment through its influence on water quality. Only a few taxa (Polyarthra spp., Colurella spp. and the cladoceran Family Moinidae) responded positively to leaf litter when water quality improved later in the experiment, indicating a switch in the role of leaf litter from a non‐trophic to a trophic pathway. 4. In spring, microcrustaceans emerged in smaller numbers from sediment sourced from cleared compared to forested wetlands, reflecting different communities in these two wetland types and/or disturbances to the sediment that interfere with emergence. 5. Although leaf litter appears not to be an important resource for zooplankton in floodplain wetlands, riparian clearing may have lasting effects on future emerging zooplankton communities. Additionally, river regulation may have considerable impacts on the influence of leaf litter on zooplankton, which has implications for the management of floodplain river systems.