Mutated sodium channel genes and elevated monooxygenases are found in pyrethroid resistant populations of Sri Lankan malaria vectors

The present status of pyrethroid resistance in vectors of malaria; Anopheles culicifacies and Anopheles subpictus, was tested in two malarious Districts, Anuradhapura and Trincomalee, of Sri Lanka. Both species were resistant to permethrin and susceptible to cypermethrin and cyfluthrin. An. subpictus were resistant to deltamethrin. λ-Cyhalothrin and etofenprox resistance was shown only by Anuradhapura An. subpictus. Although there were no differences among the populations for esterase and glutathione S-transferase activities, increased monooxygenase levels were found among Trincomalee populations. The voltage-gated sodium channel gene, the target site gene of pyrethroids, was partially sequenced to screen for mutations previously associated with insecticide resistance. The classic leucine to phenylalanine substitution, TTA to TTT, was detected in An. subpictus. It appears that both kdr type and monooxygenase resistance underlie pyrethroid resistance in these two malaria vectors of Sri Lanka.     

Feed preferences of ponies

Preference trials were conducted with mature ponies. In Trial 1, oats were compared with oats plus sucrose. Four of six pony geldings selected oats plus sucrose, but one pony demonstrated a dislike for sucrose and one selected from the bucket on the right side regardless of content. Oats, maize, barley, rye and wheat were compared in Trial 2 using six mature pony mares. Oats were the preferred grain, with maize and barley ranking second and third respectively. Wheat and rye were the least preferred. Even though the ponies demonstrated preference, the total intake at a given meal was not greatly depressed when only the less palatable grains were fed. In Trial 3, pony mares selected a diet containing 20 per cent dried distillers' grain and 80 per cent of a basal mixed diet of maize, oats, wheat bran, soybean meal, limestone and molasses over 100 per cent basal mixed diet, but selected the basal diet over diets containing 20 per cent blood meal, beet pulp or meat and bone meal and 80 per cent basal diet. They did not differentiate against diets containing 20 per cent alfalfa meal or 10 or 5 per cent meat and bone meal when the diets were compared to the basal mixed diet.     

Experimental infection of normal and immunosuppressed pigs with Pseudomonas pseudomallei

A single dose of 5 x 10(8) bacilli of Pseudomonas pseudomallei by intratracheal injection resulted in acute (21 cases) or chronic (19 cases) melioidosis in 40 of 48 pigs. Fifteen (10 acute and 5 chronic) had been immunosuppressed by cyclophosphamide before inoculation. The major clinical signs were initial fever, marked neutrophilia and, in the acute cases, respiratory distress. There were no signs of the nasal and ocular discharge, paresis or diarrhoea seen in acute cases in south-east Asia. The cyclophosphamide treatment caused a significant decrease in the neutrophil count by 7 d after inoculation in all 15 immunosuppressed pigs, and all were culture positive at necropsy. Eight of the 33 non-treated pigs were culture negative at necropsy. Pigs overcoming the initial phase of infection had more abscess-like nodules that were bacteriologically sterile at necropsy than the pigs with acute cases of melioidosis. P. pseudomallei was isolated predominantly from the spleen, lungs and the injection site. Although only one strain was used in this study, it is likely that Australian strains of P. pseudomallei are not as virulent as the south-east Asian isolates.     

Convenient large-scale purification of yessotoxin from Protoceratium reticulatum culture and isolation of a novel furanoyessotoxin

Yessotoxins from a large-scale culture (226 L) of Protoceratium reticulatum strain CAWD129 were harvested by filtration followed by solid-phase extraction. The extract was purified by column chromatography over basic alumina and reverse-phase flash chromatography to afford pure yessotoxin (193 mg). Isolation of yessotoxin was greatly facilitated by selection of a strain which did not produce analogues that interfered with yessotoxin isolation. In addition to yessotoxin, numerous minor yessotoxins were detected by LC-MS in other fractions. From one of these, an early eluting minor analogue with the same molecular weight as yessotoxin and a similar mass spectrometric fragmentation pattern was isolated. This analogue was identified by NMR and mass spectrometry as a novel yessotoxin analogue containing a furan ring in the side chain. This finding reveals biosynthetic flexibility of the yessotoxin pathway in P. reticulatum and confirms earlier findings of production of many minor yessotoxin analogues by this alga. Production of these analogues appeared to be a constitutive trait of P. reticulatum CAWD129.     

Significance of wild species and primitive forms for potato breeding

Three stages in the history of the utilization of wild potatoes are outlined, and it is suggested that we are now entering on a fourth stage, typified by a fuller international co-operation than has hitherto been possible.The availability of useful genes is considered in the light of our knowledge of the crossability and evolutionary relationships of potato species. Breeding mechanisms in species at various levels of ploidy are shown to play an important part in speciation, and the significant role of asexual reproduction in potatoes is discussed.The geographical localization of most genes carrying resistance to Phytophthora, viruses, Heterodera, Leptinotarsa and frost is discussed. Certain explanations to account for this localization are put forward.Samenvatting Drie stadia in de geschiedenis van het gebruik van wilde aardappelsoorten en primitieve aardappelrassen worden genoemd. Omstreeks 100 jaar geleden waren nieuwe rassen nodig ter bestrijding van degeneratieziekten, terwijl omstreeks 1909 het wilde materiaal voor het kweken op ziekteresistentie ter hand werd genomen. Het 3e stadium begon in 1925 toen de eerste grote expeditie werd gehouden om materiaal te verzamelen voor een onderzoek naar de genetische variatie van de aardappelsoorten. Thans is men gekomen in het 4e stadium, nl. een nauwere internationale samenwerking dan tot nu toe mogelijk was.Schrijver geeft een overzicht van de perspectieven voor het kweken op resistentie tegen Phytophthora, virusziekten, Heterodera, coloradokever en vorst. Het is gebleken dat bepaalde genen in bepaalde gebieden voorkomen (geographical localization).

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Zusammenfassung Bedeutung der Wildkartoffeln und Primitivformen für die Kartoffelzüchtung In der Geschichte der Verwertung der Wildkartoffeln werden drei Stufen abgezeichnet und die Ansicht vertreten, daß wir eben in eine vierte eintreten, welch durch vollere internationale Zusammenarbeit als bisher möglich gewesen ist, charakterisiert wird.Die Tatsache, daß wertvolle Gene zur Verfügung stehen, wird im Lichte unserer Kenntnisse der Kreuzbarkeit und der Entwicklungsbeziehungen von Kartoffelarten betrachtet.Es wird aufgezeigt, daß Reproduktionsmechanismen in Arten auf verschiedenen Stufen der Ploidie eine wichtige Rolle in der Artzüchtung spielen, ferner wird die wichtige Rolle asexueller Reproduktion in Kartoffeln behandelt.Die geographische Lokalisierung der meisten Genen, die gegen Phytophthora, Viren, Heterodera, Leptinotarsa und Frost resistent sind, ist hier behandelt. Erklärungen für diese Lokalisierung werden hier vorgeschlagen.Zusammenfassung In der Geschichte der Verwertung der Wildkartoffeln werden drei Stufen abgezeichnet und die Ansicht vertreten, daß wir eben in eine vierte eintreten, welche durch vollere internationale Zusammenarbeit als bisher möglich gewesen ist, charakterisiert wird.Die Tatsache, daß wertvolle Gene zur Verfügung stehen, wird im Lichte unserer Kenntnisse der Kreuzbarkeit und der Entwicklungsbeziehungen von Kartoffelarten betrachtet.Es wird aufgezeigt, daß Reproduktionsmechanismen in Arten auf verschiedenen Stufen der Ploidie eine wichtige Rolle in der Artzüchtung spielen, ferner wird die wichtige Rolle asexueller Reproduktion in Kartoffeln behandelt.Die geographische Lokalisierung der meisten Genen, die gegen Phytophthora, Viren, Heterodera, Leptinotarsa und Frost resistent sind, ist hier behandelt. Erklärungen für diese Lokalisierung werden hier vorgeschlagen.

     

Crossability relationships of andean potato varieties of three ploidy levels

Summary The formation of triploids in 4x×2x crosses was studied in primitive potato varieties from the Andes of Peru and Bolivia. Triploid frequencies were as high as 80–100% in some crosses, although the actual number of seeds was low. The triploid block varied according to the tetraploid parent, and was never entirely absent. The likelihood of triploid formation was studied in 4x×2x crosses where pollen from both tetraploids and diploids of known genotype was used. Even though the diploids were chosen for their non-production of 2n gametes, as detected in pollen grain size, 66% of the hybrids were tetraploid. The amount and probability of gene-flow between the tetraploid and diploid gene-pools, either directly through 2n gametes or through triploid bridges was examined. Most of the 20 cultivars of S. x chaucha produced seed in crosses with tetraploids and diploids, although the fertility of the latter crosses was four times higher. The female fertility of some of the triploids thus allows them to exchange genes with the tetraploids and diploids, although gene-flow occurs more rapidly through direct transfer from diploids to tetraploids via 2n gametes.     

The nature of Solanum × chaucha Juz. et Buk., a triploid cultivated potato of the South American Andes

Summary The variation in Solanum × chaucha Juz. et Buk. (2n=3x=36) was studied using 114 accessions from the Potato Collection maintained by the International Potato Center. These accession represented less than 5% of the collection originally screened for ploidy. Twenty morphological characters of the tubers, inflorescences and leaves were scored. The accessions were grouped into 20 morphotypes on the basis of the tuber characters. Two-qualitative characters, red-anther tip and sky-blue flowers were diagnostic of 4 morphotypes, but the variation of the quantitative characters overlapped among morphotypes, and were of limited value. Electrophoretic separation of tuber proteins in 7.5% polyacrylamide gels generally confirmed the morphotype groupings. It is concluded that each of the morphotypes represents a single genotype, and these are named according to the International Code of Nomenclature for Cultivated Plants. The variation within S. × chaucha apparently has been restricted by its hybrid origin.     

The Importance of the Bolivian Wild Potato Species in Breeding for Globodera pallida Resistance

Screening for resistance to the potato cyst nematode, Globodera pallida, in potatoes from. Bolivia, was carried out in 1983 and 1984, using a mixture of four nematode populations representing pathotypes Pa₁, Pa₂ and Pa₃ From the 66 accessions of 17 species and subspecies evaluated, highly resistant genotypes were identified in 21 accessions from seven species. All had Pf/Pi values of 2 or less, whereas the susceptible control, Solanum tuberosum cv. ‘Disiree’ had Pf/Pi values of more than 2G in both tests. Two diploid wild species, S. brevicaule and S. leptophyes, showed the best resistant. The geographical distributional of resistant populations and the evolution of resistance in wild potato populations are discussed.