Searching for wheat resistance to aphids and wheat bulb fly in the historical Watkins and Gediflux wheat collections.

Insect pests can reduce wheat yield by direct feeding and transmission of plant viruses. Here we report results from laboratory and field phenotyping studies on a wide range of wheat, including landraces from the Watkins collection deriving from before the green revolution, more modern cultivars from the Gediflux collection (north-western Europe) and modern UK Elite varieties, for resistance to the bird cherry-oat aphid, Rhopalosiphum padi (Homoptera: Aphididae) and the English grain aphid, Sitobion avenae (Homoptera: Aphididae). A total of 338 lines were screened for R. padi and 340 lines for S. avenae. Field trials were also conducted on 122 Watkins lines to identify wheat bulb fly, Delia coarctata, preference on these landraces. Considerable variation was shown in insect performance among and within different wheat collections, with reduced susceptibility in a number of varieties, but phenotyping did not identify strong resistance to aphids or wheat bulb fly. Field trials showed within collection differences in aphid performance, with fewer aphids populating lines from the Watkins collection. This differs from development data in laboratory bioassays and suggests that there is a pre-alighting cue deterring aphid settlement and demonstrates differences in aphid preference and performance on older plants in the field compared with seedlings in the laboratory, highlighting the need for phenotyping for aphid resistance at different plant growth stages. No association was identified between performance of the different insect species on individual varieties, potentially suggesting different nutritional requirements or resistance mechanisms.

Triticum monococcum lines with distinct metabolic phenotypes and phloem-based partial resistance to the bird cherry-oat aphid Rhopalosiphum padi.

Crop protection is an integral part of establishing food security, by protecting the yield potential of crops. Cereal aphids cause yield losses by direct damage and transmission of viruses. Some wild relatives of wheat show resistance to aphids but the mechanisms remain unresolved. In order to elucidate the location of the partial resistance to the bird cherry-oat aphid, Rhopalosiphum padi, in diploid wheat lines of Triticum monococcum, we conducted aphid performance studies using developmental bioassays and electrical penetration graphs, as well as metabolic profiling of partially resistant and susceptible lines. This demonstrated that the partial resistance is related to a delayed effect on the reproduction and development of R. padi. The observed partial resistance is phloem based and is shown by an increase in number of probes before the first phloem ingestion, a higher number and duration of salivation events without subsequent phloem feeding and a shorter time spent phloem feeding on plants with reduced susceptibility. Clear metabolic phenotypes separate partially resistant and susceptible lines, with the former having lower levels of the majority of primary metabolites, including total carbohydrates. A number of compounds were identified as being at different levels in the susceptible and partially resistant lines, with asparagine, octopamine and glycine betaine elevated in less susceptible lines without aphid infestation. In addition, two of those, asparagine and octopamine, as well as threonine, glutamine, succinate, trehalose, glycerol, guanosine and choline increased in response to infestation, accumulating in plant tissue localised close to aphid feeding after 24 h. There was no clear evidence of systemic plant response to aphid infestation.

New roles for cis-jasmone as an insect semiochemical and in plant defense.

cis-jasmone, or (Z)-jasmone, is well known as a component of plant volatiles, and its release can be induced by damage, for example during insect herbivory. Using the olfactory system of the lettuce aphid to investigate volatiles from plants avoided by this insect, (Z)-jasmone was found to be electrophysiologically active and also to be repellent in laboratory choice tests. In field studies, repellency from traps was demonstrated for the damson-hop aphid, and with cereal aphids numbers were reduced in plots of winter wheat treated with (Z)-jasmone. In contrast, attractant activity was found in laboratory and wind tunnel tests for insects acting antagonistically to aphids, namely the seven-spot ladybird and an aphid parasitoid. When applied in the vapor phase to intact bean plants, (Z)-jasmone induced the production of volatile compounds, including the monoterpene (E)-beta-ocimene, which affect plant defense, for example by stimulating the activity of parasitic insects. These plants were more attractive to the aphid parasitoid in the wind tunnel when tested 48 h after exposure to (Z)-jasmone had ceased. This possible signaling role of (Z)-jasmone is qualitatively different from that of the biosynthetically related methyl jasmonate and gives a long-lasting effect after removal of the stimulus. Differential display was used to compare mRNA populations in bean leaves exposed to the vapor of (Z)-jasmone and methyl jasmonate. One differentially displayed fragment was cloned and shown by Northern blotting to be up-regulated in leaf tissue by (Z)-jasmone. This sequence was identified by homology as being derived from a gene encoding an alpha-tubulin isoform.

Reactivity of the new monoclonal antibody '22' with meningococcal strains isolated from patients and carriers in Greece.

Previous studies found that the majority of Neisseria meningitidis isolates from either patients or carriers in Greece do not react with the monoclonal antibodies used at present in the whole-cell ELISA (WCE) for determination of serotype and subtype antigens. A new monoclonal antibody designated '22' produced by the National Meningococcal Reference Laboratory in the Czech Republic was assessed in the whole-cell ELISA with 257 non-typable meningococcal strains from both patients (52) and carriers (205). The carrier strains included 34 non-typable isolates from two immigrant populations: ethnic Greeks who have immigrated from Russia since 1989 (19/75) and Kurdish refugees (15/34). Approximately 10% of the meningococcal strains isolated from patients and 11.7% of the carrier strains reacted with the reagent. Although the majority of meningococcal isolates from resident Greeks were not typable with the antibody, 11/19 (57.9%) of the carrier strains from Russian immigrants and 4/15 (20%) of those from the Kurdish refugees reacted with the new reagent.

Meningococcal infection in Scotland, 1995 to 1997.

The incidence of meningococcal infection in Scotland was 4.1 cases per 100 000 population in 1996 compared with 3.8/100 000 in 1995 (210 cases reported in 1996 compared with 193 in 1995). There were 14 deaths, representing a crude case fatality rate of 6.

Serogroup-specific epidemiology of Streptococcus pneumoniae: associations with age, sex, and geography in 7,000 episodes of invasive disease.

A study sample of 7,010 episodes of invasive Streptococcus pneumoniae disease was obtained by combining 13 existing datasets. Disease episodes due to each of 12 pneumococcal serogroups (1, 3-9, 14, 18, 19, and 23) were then compared with episodes in a constant internal control group to describe serogroup-specific variations in disease frequency by age, sex, and geographic origin. The results are presented as odds ratios (with 95% confidence intervals) derived by logistic regression, with adjustment for the major confounders, including dataset of origin. Variation in the male:female ratios between serogroups is small, suggesting that capsular characteristics are an unlikely explanation for the male preference of S. pneumoniae. Serogroups associated with higher nasopharyngeal prevalence (e.g., 19 and 24) are relatively more common in Europe and North American, while the invasive serotypes 1 and 5 are much more common in South America. The custom of reporting serogroup frequencies in two age groups, children and adults, conceals much of the variation in the age distributions across the whole span of life. The reduction of risk associated with serogroups 6, 14, 18, 19, and 23 beyond childhood follows different gradients, being most abrupt in serogroups 14 and most gradual in serogroup 18. The relative risk of disease with serotype 1 declines steadily throughout life, while with serotypes 3 and 8 it increases over middle age. Serogroups 7 and 23 are found unusually frequently in the third decade of life. Because of the wide differences in the epidemiology of individual serogroups of S. pneumoniae, it is questionable whether pneumococcal infection should continue to be classified as a single disease entity.

Winter host component reduces colonization by bird-cherry-oat aphid,Rhopalosiphum padi (L.) (homoptera, aphididae), and other aphids in cereal fields.

Methyl salicylate, a volatile component ofPrunus padus, the winter host ofRhopalosiphum padi, was found to reduce colonization of the summer host by this aphid. The compound was identified by gas chromatographic analysis coupled with recordings from cells in the primary rhinarium on the sixth antennal segment of the aphid. Methyl salicylate eliminated the attractancy of oat leaves to spring migrants in olfactometer tests. In Sweden, this compound significantly decreased colonization of field grown cereals byR. padi and in the U.K., populations ofSitobion avenae andMetopolophium dirhodum were significantly lower on treated plots.

New 23-valent pneumococcal vaccine in relation to pneumococcal serotypes in systemic and non-systemic disease.

The serotype distribution of 3631 strains of Streptococcus pneumoniae, isolated from various specimens obtained from patients was determined by coagglutination and included serotyping within a total of 13 serogroups. The results of serotyping of isolates from Scotland demonstrated that the new 23-valent pneumococcal vaccine includes serotypes which accounted for 91% strains associated with systemic disease and 79% strains isolated from other anatomical sites. Altogether, 114 strains (3.1%) were not typable because they did not possess a type-specific capsule; these were commonly isolated from eyes (12%).

A comparison of the distribution of pneumococcal types in systemic disease and the upper respiratory tract in adults and children.

The serotype distribution of 874 strains of Streptococcus pneumoniae was determined in relation to patients' age and to frequency of isolation from systemic disease. Types 14 and 18, in pre-school children, and types 1, 4, 7, 8 and 12 in patients over 5 years of age were significantly associated with systemic disease whereas type 23 in pre-school children, and type 6 in older patients was associated with upper respiratory tract carriage. No significant difference was found in the incidence of other types in systemic disease compared to upper respiratory tract carriage. Fifteen diagnostic pneumococcal antisera (to types 1, 3, 4, 6, 7, 8, 9, 11, 12, 14, 17, 18, 19, 22 and 23) sufficed for typing 87% of strains.

An alternative approach to typing of Streptococcus pneumoniae strains by coagglutination.

The coagglutination test, which uses staphylococcal protein A for typing strains of Streptococcus pneumoniae was extended to include typing within 13 groups. Typing was performed using the factors remaining in group antisera after absorption with a strain of a type within the group. 93 of 99 strains of S. pneumoniae, which belonged to one of the 13 groups included in the 23 valent vaccine formulation were correctly identified when compared to the capsular reaction test.

Serotyping of Streptococcus pneumoniae strains by coagglutination.

The coagglutination test, which uses staphylococcal protein A, for serotyping strains of Streptococcus pneumoniae, was extended to include serotyping within serogroups. Serotyping was performed with "factor sera" prepared in the laboratory. Fifty one strains of S pneumoniae, which belonged to one of the seven serogroups included in the 14 valent vaccine formulation, were tested, and no inconsistency was found when compared with the capsule swelling reaction.

Effect of iron poly (sorbitolgluconic acid) complex on urinary cellular excretion.

The intramuscular injection of 250 mg iron poly (sorbitol-gluconic acid) complex caused no increase in urinary cellular or bacterial excretion in 8 patients with chronic pyelonephritis, 4 patients with non-infective renal disease, and 4 controls. However, in 4 patients with chronic infective disease of the renal tract given 500 g there was a significant increase in cellular excretion. This response was not seen in 2 control patients, nor in 2 patients with non-infective renal disease. Using a differential staining technique, this increase in urinary cellular excretion was found to be due, not to leucocytes, but to renal tubular cells. The precise significance of this is unclear, but there would be concern that the high concentration of excreted iron was providing a 'toxic' insult to susceptible, infection-damaged cells.