Current status of the Drosophila melanogaster species-group (Diptera)

Abstract. The Drosphila melanogaster species-group, established by Sturtevant (1942) for fourteen species, is now known to contain 115 described species here divided into twelve named subgroups (including one newly proposed), as well as further undescribed species. Three of the species, melanogaster, simulans and ananassae , are cosmopolitan; two others, kikkawai and malerkotliana , are widespread in the southern hemisphere, the latter apparently a recent introduction to South America. The greatest numbers of species otherwise occur in the Oriental region with smaller numbers in the Ethiopian, eastern Palaearctic and Australian regions and in several islands of the South Pacific. D.rajasekari and D.raychaudhurii are synonymized with D.biamipes;also D.andamanensis Parshad & Singh is synonymized with D.andamanensis Gupta & Raychaudhuri.     

Glitoria yellow vein virus, a tymovirus from Kenya

Clitoria yellow vein virus (CYW) was found in Clitoria ternatea and Abrus precatorius in coastal districts of Kenya, but was not detected in food legume crops. When transmitted by inoculation of sap, CYW infected many species in the Papilionaceae, commonly causing yellowing of secondary and smaller leaf veins. All the economically important food legumes grown in the area of occurrence were very susceptible, so that CYW is potentially very important. The virus also infected okra (Hibiscus esculentus) and species in the Solanaceae, but none of many species of Cucurbitaceae. CYW is serologically closely related to cocoa yellow mosaic and kennedya yellow mottle viruses, and more distantly to okra mosaic and desmodium yellow mottle viruses. Other properties of CYW^ typical of the tymoviruses include particle morphology (particle diameter c. 28 nm; two components) with sedimentation coefficients of 50S (top) and 109S (bottom); molecular weight of protein sub-units c. 20000; thermal inactivation point c. 72 ^oC; and longevity in vitro c. 3 wk.     

Variation in the glucosinolate content of oilseed rape (Brassica napus L.) leaves

The glucosinolate content of oilseed rape {Brassica napus) leaves was monitored over the growth period 30–70 days after planting, and a comparison made between a single-low cultivar (low in erucic acid), Bienvenu, and a double-low cultivar (low in erucic acid and glucosinolate), Cobra. In older, fully-expanded leaves the glucosinolate concentration was very low (< 0.3 μmol/ml tissue water) and did not alter during the course of the experiment. In developing sixth leaves glucosinolate content increased rapidly and reached a maximum concentration (4–5 μmol/ml tissue water) 40 days after planting (6 days after leaf emergence). The concentration then declined, to about 1 μmol/ml after 60 days although the total glucosinolate content in leaves continued to increase until 50 days; much of the reduction in concentration was simply a result of leaf expansion. No major differences were seen between the two varieties in total glucosinolate content or in the individual compounds present. Cv. Cobra developed more quickly than cv. Bienvenu so direct comparison between leaves of the two cultivars was complex. When comparing the glucosinolate content of oilseed rape leaves, between cultivars or between treatments, it is vital to ensure that carefully matched leaves of comparable developmental age are selected.     

Purification of maize streak virus and its relationship to viruses associated with streak diseases of sugar cane and Panicum maximum

Maize streak virus (MSV) was purified by homogenising infected leaf tissue in 0·01 m pH 3·9 phosphate buffer and clarifying the extract with n-butanol (7 ml/100 ml extract). Purified preparations contained particles 20 nm in diameter, some occurring singly, but most occurring in pairs, forming structures of 30 × 20 nm. The sedimentation coefficients of single and paired particles were 54 and 76 S respectively. When centrifuged in sucrose density gradients preparations made by extracting leaves at pH 3·9 gave a single intense light-scattering zone containing paired particles. Preparations made at pH 5·9 or 7·9 gave one or two additional upper zones containing single particles and fragmented material. Preparations treated with 0·05 or 0·1 m ethylene diamine tetra-acetic acid, disodium salt, (EDTA) contained no paired particles, few single particles and much fragmented material. In immunoelectrophoresis, the major component in preparations without EDTA migrated to the cathode whereas that in EDTA-treated preparations migrated to the anode. Virus isolates from streak-diseased sugarcane and guinea grass (Panicum maximum) were serologically related to MSV and had similar particles with identical sedimentation coefficients. No such particles were seen in purified preparations of healthy maize, sugarcane, or guinea grass. The viruses from sugarcane and guinea grass are probably host-adapted and are referred to correctly as the sugarcane and guinea grass strains of MSV. MSV probably contains single-stranded RNA, and the cryptogram is (R)/1:*/*:S/S:S/Au.     

Thermodynamics and Kinetics of MTBE Degradation: A Density Functional Theory Study

Computational studies using density functional theory can help define which of a variety of reactions may be involved in the degradation of the fuel oxygenate methyl tert-butyl ether (MTBE). It is shown that hydrolysis of MTBE in the vapor phase or in neutral aqueous media, as well as its unimolecular decomposition, are not significant degradation mechanisms. The acid catalyzed hydrolysis of MTBE is a more feasible degradation pathway and is shown to proceed via tert-butyl carbonium ion formation. Hydrogen abstraction is shown to be the dominant first step in the degradation of MTBE initiated by hydroxyl radicals.     

The subgenus Scaptodrosophila (Diptera: Drosophilidae)

Four major subgenera, Drosophila, Sophophora, Hirtodrosophila and Scaptodrosophila, and several minor subgenera, have been recognized in the genus Drosophila. The hitherto little studied subgenus Scaptodrosophila, possessing a complicated synonymy, contains 144 named species, or about 11% of the total described in the genus; it is likely that many more Scaptodrosophila species await discovery. Scaptodrosophila probably originated in tropical Asia, and the greatest Scaptodrosophila faunas occur in Asia, south-east Asia, New Guinea, Australia and Africa, with very few species in north and south America and Europe. Scaptodrosophila species usually possess a pair of prescutellar bristles, a propleural bristle, and three large subequal sternopleural bristles; other morphological features are more variable. Ecological information concerning the majority of Scaprodrosophila species is scanty or absent, but known feeding or breeding sites include tree sap, fungi, fruit, flowers and 1eaf litter; larvae of at least one species are gall forming in plant tissues. The establishment of species groups is complicated by lack of detailed knowledge of many species, but six groups containing four or more species are recognized.