Genetic analysis of bacterial blight resistance in seventy-four cultivars of rice,Oryza sativa L.

Summary The genetics of resistance to bacterial blight, Xanthomonas oryzae (Uyeda and Ishiyama) Dowson, for 74 cultivars of rice, Oryza sativa L., was studied. The PX061 isolate of bacterial blight from the Philippines was used for inoculation of parental and hybrid populations. Single dominant genes at the Xa 4 locus convey resistance in 38 cultivars. Of these, 18 are resistant at all stages of plant growth and thus have the Xa 4 ^aallele for resistance. However, 20 are susceptible up to maximum tillering stage but are resistant at booting and flowering stages. These cultivars have the Xa 4 ^ballele for resistance. Thirty-two cultivars have single recessive genes for resistance which are allelic to xa 5.The resistance in DV85, DV86 and DZ78 is conditioned by two genes. At maximum tillering stage xa 5 conveys resistance. However, at later growth stages an additional dominant gene, designated Xa 7 in DZ78, also gives resistance. The dominant genes of DV85 and DV86 are probably allelic to Xa 7. Xa 7 segregates independently of Xa 4, xa 5 and Xa 6, however like Xa 6, it conveys resistance at booting and post-booting stages only.The resistance in PI 231129 is conditioned by a single recessive gene, designated xa 8. It also segregates independently of Xa 4, xa 5 and Xa 6.     

Genetic analysis of resistance to whitebacked planthopper in twenty-one varieties of rice,Oryza sativa L.

Summary The inheritance of resistance to whitebacked planthopper Sogatella furcifera (Horvath) was studied in 21 rice varieties. Reactions of F₁; F₂ and F₃ progenies of the crosses of 21 resistant varieties with the susceptible variety TN 1 revealed that a single dominant gene governs resistance in Mushkan 41, Santhi, Siahnakidar 195, SM2-34, Tirisurkh 251, Zirijowaian 245, 18, 24A, 39, 76 S, 78, 180, 213 B, 267, 293, CI 6037-4, NP97, S39 JKW and Bansphul. In varieties 65 and 274 A, resistance is governed by one dominant and one recessive gene which segregate independently of each other. Tests for allelism with the Wbph 1 gene originally identified in N 22 revealed that the dominant gene present in all the test varieties is the same as Wbph 1. Further studies are required to determine the allelic relationships of the recessive gene found in varieties 65 and 274 A.     

Genetic analysis of brown planthopper resistance in twenty varieties of rice,Oryza saliva L.

Summary The inheritance of resistance to brown planthopper, Nilaparvata lugens (Stol.), of 20 rice cultivars was studied. Single dominant genes that are allelic to Bph 3 condition the resistance in cultivars Ptb 19, Gangala (Acc. 7733), Gangala (Acc. 15207), Horana Mawee, Kuruhondarwala, Mudu Kiriyal and Muthumanikam. Single recessive genes that are allelic to bph 4 govern the resistance in cultivars Gambada Samba, Heenhoranamawee, Hotel Samba, Kahata Samba, Kalukuruwee, Lekam Samba, Senawee, Sulai, Thirissa and Vellai Illankali. The resistance in Ptb 33, Sudu Hondarwala, and Sinna Sivappu is governed by one dominant and one recessive gene which segregate independently of each other. The dominant resistance genes in these cultivars appear allelic to either Bph 1 or Bph 3. Similarly, the recessive genes in these cultivars seem allelic to either bph 2 or bph 4. Further investigations are needed to conclusively determine the allelic relationships of resistance genes in Ptb 33, Sudu Hondarwala and Sinna Sivappu.     

The mucin profiles of normal gastric mucosa, intestinal metaplasia and its variants and gastric carcinoma

Summary Human gastrectomy specimens, including 48 carcinomas and 25 selected benign cases showing extensive intestinal metaplasia (IM), were examined in detail histologically and histochemically. IM was classified into complete (type I), incomplete without sulphomucins (type IIA) and incomplete with sulphomucins (type IIB). Type IIB was associated with intestinal but not diffuse cancers (P<0.01) or benign lesions (P<0.01). The mucin profiles of IIB IM were similar to intestinal cancers with sulphomucins predominating overN-acetylsialomucins.O-acetylsialomucins were not seen in IIB IM or tumours but were observed in complete or type IIM. These findings suggest a histogenic link between incomplete IM secreting sulphomucins (or colonic metaplasia) and intestinal cancers of the human stomach.     

Degradation stages of the oak forests in the area of Algiers

Long lasting human impact on the natural Mediterranean vegetation is the reason for its degradation. Uncontrolled felling of trees, fire and overgrazing are the most important ecological causes of this process.Geobotanical investigations made in the area of Algiers facilitated the characterization of degradation changes in the structure of vegetation and in the floristic composition in all the degradation stages.Under the influence of the degradation factors, mentioned above, the oak forests, growing on different, more or less calcareous substrates, are transformed into various shrub formations, mainly into many types of maquis and garrigue. The floristic composition of these communities is given in Table 2.Further degradation leads to widespread Cistus-formations and then to palmitto, a formation created by the dwarf palm (Chamaerops humilis).When the anthropopressure becomes stronger even this dwarf palm retreats. Loose swards, replacing the palmitto formation, often cannot stop the subsequent degradation. Bare rock is the extreme, relatively rare stage of forest degradation in this area.The most common form of natural regeneration is the invasion of Pinus halepensis, observed in all degradation stages identified. This pine is also one of trees, most commonly planted on mountain slopes to prevent their erosion.     

Hypoxia Tolerance of Two Haplochromine Cichlids: Swamp Leakage and Potential for Interlacustrine Dispersal

The ability to tolerate hypoxia in some haplochromine cichlid fishes contributes to the richness of habitats occupied by the lineage and may be important in interlacustrine dispersal through swampy channels. Lacustrine members of the genus Astatotilapia tend to be ecologically plastic but are rarely encountered in the interior of dense swamps. A notable exception is seen in the swamp corridor that joins Lake Kabaleka with Lake George, Uganda, where one species (Astatotilapia wrought-iron) is abundant, and a second species, A. aeneocolor, is rare. Both species are abundant in the open waters of the main lake. In this paper, we compare physiological (oxygen consumption) and behavioral indicators of hypoxia tolerance between A. wrought-iron from swamp and open-water habitats and between the two species of Astatotilapia. When exposed to progressive hypoxia, all fish used aquatic surface respiration (ASR); however, swamp-dwelling A. wrought-iron showed lower gill ventilation rates prior to the initiation of ASR, higher pre-ASR aggression rates, higher swimming speed during ASR, and a higher rate of bubble exchange than both the open-water group of A. wrought-iron and A. aeneocolor. These differences may reflect interpopulational variation in selection pressure for low-oxygen tolerance between swamp and open-water habitats. Several lines of evidence suggest that A. wrought-iron was in general more hypoxia tolerant than A. aeneocolor. These include a lower ASR₉₀ threshold, a drop in gill ventilation rate with the onset of ASR, and lower rate of equilibrium loss under extreme hypoxia in A. wrought-iron. The routine metabolic rate and critical oxygen tension did not differ between swamp-dwelling and open-water A. wrought-iron, or between A. wrought-iron and A. aeneocolor. Comparative data on the ASR thresholds and critical oxygen tensions of the Astatotilapia species from Lake Kabaleka and other East African cichlids suggest intermediate hypoxia tolerance. Nevertheless, our study suggests that some generalized lacustrine haplochromines may leak through swamp corridors even under relatively extreme conditions.     

Effect of Gamma Irradiation on Embryogenic Avocado Cultures and Somatic Embryo Development

Embryogenic avocado cultures were exposed to ionizing irradiation in order to determine its effect on proliferation and subsequent somatic embryo development. The approximate PD₅₀ as determined by linear regression is 35 Gy 2 weeks after irradiation for Fuerte 2.11.1 and 4 weeks after irradiation for T362 2.11.1. Irradiation of embryogenic cultures did not significantly affect the number of early stage Fuerte 2.11.1 somatic embryos that developed directly from irradiated cultures; however, 10–50 Gy inhibited somatic embryo development. Irradiation of T362 2.11.1 embryogenic cultures at 25–50 Gy inhibited the number of intermediate and mature stages of somatic embryos that developed directly from irradiated cultures, and 50 Gy inhibited somatic embryo maturation. Inhibition of somatic embryo development could be partially offset by proliferation of irradiated embryogenic cultures as suspensions. Irradiation up to 10 Gy significantly increased the number of mature Fuerte 2.11.1 somatic embryos that developed from suspension cultures. Irradiation with doses up to 25 Gy stimulated development of heart stage T362 2.11.1 somatic embryos; however, mature somatic embryo development was suppressed at dosages of 10 Gy and greater.     

Molecular mapping of a new gene Rrs4 CI 11549 for resistance to barley scald (Rhynchosporium secalis)

Doubled haploid (DH) progeny from a cross between the scald susceptible barley (Hordeum vulgare L.) cultivar Ingrid and the resistant accession CI 11549 (Nigrinudum) was evaluated for resistance in the pathogen Rhynchosporium secalis (Oudem) J.J. Davis. Two linked and incompletely dominant loci confer resistance CI 11549 against isolate 4004. One is an allele at the complex Rrs1 locus on chromosome 3H close to the centromere; the other is located 22 cM distally on the long arm. The latter locus is designated Rrs4. In BC₃-lines into Ingrid from CI 2222 (another Nigrinudum) resistance seems governed by one locus close to the telomeric region of chromosome 7H, probably allelic to Rrs2. In neither case did we find any trace of the recessive gene rh8 reported to be present in Nigrinudum. Various resistance donors of Ethiopian origin designated as Nigrinudum, Jet or Abyssinian were identical to a great extent with respect to markers, but differed in resistance to different isolates of scald or in barley yellow dwarf virus (BYDV) resistance. The implications for their use as differentials in scald tests and screening of germplasm collections are discussed.     

Structure of the cytochrome <Emphasis Type="Italic">b</Emphasis><Subscript>6</Subscript><Emphasis Type="Italic">f</Emphasis> complex: new prosthetic groups,Q-space,and the ‘hors d’oeuvres hypothesis’ for assembly of the complex

3-Å crystal structures of the cytochrome b₆f complex have provided a structural framework for the photosynthetic electron transport chain. The structures of the 220,000 molecular weight dimeric cytochrome b₆f complex from the thermophilic cyanobacterium, Mastigocladis laminosus (Kurisu et al. 2003, Science 302: 1009–1014), and the green alga, Chlamydomonas reinhardtii (Stroebel et al. 2003, Nature 426: 413–418), are very similar. The latter is the first structure of a integral membrane photosynthetic electron transport complex from a eukaryotic source. The M. laminosus and C. reinhardtii structures have provided structural information and experimental insights to the properties and functions of three native and novel prosthetic groups, a chlorophyll a, a -carotene, and a unique heme x, one copy of which is found in each monomer of the cytochrome b₆f complex, but not the cytochrome bc₁ complex from the mitochondrial respiratory chain of animals and yeast. Several functional insights have emerged from the structures including the function of the dimer; the properties of heme x; the function of the inter-monomer quinone-exchange cavity; a quinone diffusion pathway through relatively narrow crevices or portals; a modified reaction scheme for n-side quinone redox reactions; a necessarily novel mechanism for quenching of the bound chlorophyll triplet state; a possible role for the bound chlorophyll a in activation of the LHC kinase; and a structural and assembly role for the four small PetG, L, M, and N subunits. An hors doeuvres hypothesis for assembly of the complex is proposed for the small hydrophobic stick or picket fence polypeptides at the periphery of the complex, based on the cis-positive orientation of the small hydrophobic subunits and the toothpick binding mode of the -carotene.     

Synthesis of hexaploid (AABBCC) somatic hybrids: a bridging material for transfer of ‘tour’ cytoplasmic male sterility to different Brassica species

Most of the alloplasmic cytoplasmic male sterility (CMS) systems are known to be associated with a number of floral abnormalities that result from nuclear-cytoplasmic incompatibilities. One such system, tour, which is derived from Brassica tournefortii, induces additional floral abnormalities and causes chlorosis in Brassica spp. While the restorer for this CMS has been reported to be present in B. napus, in B. juncea, where the abnormalities are more pronounced, no restorer has yet been identified. Rectification of these floral abnormalities through mitochondrial recombinations and chloroplast replacement might result in the improvement of this CMS system. As organelle recombinations can possibly be achieved only by somatic cell hybridization, fusion experiments were carried out between hygromycin-resistant B. juncea AABB carrying tour cytoplasm and phosphinotricin-resistant, normal B. oleracea CC to generate AABBCC hexaploid somatic hybrids. The presence of selectable marker genes facilitated the selection of hybrids in large numbers. The resulting hybrids showed wide variation in floral morphology and organelle composition. Regenerants with normal, male-sterile flowers having recombinant tour-or oleracea-type mitochondria and oleracea-type chloroplasts were obtained. Hybrids with male-fertile flowers were also obtained that had recombined tour mitochondria. The AABBCC hexaploid hybrids synthesized in the present study were successfully utilized as a bridging material for transferring variability in the organelle genome simultaneously to all the digenomic Brassica species, and all of these hybrids are now being stabilized through repeated backcrosses to the allopolyploid crop brassicas.     

Satellited chromosomes,systematics and phylogeny inTaraxacum (Asteraceae)

A survey is made of the occurrence, nature and frequency of satellited chromosomes in the agamospermous genusTaraxacum. Species belonging to the 10 sections thought to be most primitive in the genus lack satellited chromosomes. In most other sections, a characteristic satellited chromosome is seen with a large euchromatic region distal to the presumed nucleolar oraniser region (NOR). In sections of a precursor type, there is always one chromosome of this Taraxacum type per haploid genome. In sections thought to be of an advanced type the number of such satellited chromosomes is very unstable, sometimes even within the same tissue. In sectionHamata, two such satellited chromosomes are invariably found in triploids. This finding strongly supports the integrity of this section, suggests that the species of the section are monophyletic, and have evolved from a single ancestor subsequent to the occurrence of obligate agamospermy. In three sections of the genus, satellited chromosomes of the conventional type with a very small distal euchromatic region distal to the NOR are reported for the first time in the genus.     

The complex life-cycle of a polymorphic prokaryote epibiont of the photosynthetic bacterium Chromatium weissei

In natural populations of the anaerobic phototrophic bacterium Chromatium weissei, many cells support a prokaryotic epibiont. This epibiont appears in several forms, all from the life cycle of a single species. A typical epibiont consists of one to five flattened coccoid cells stacked one above the other, perpendicular to the C. weissei surface. The cells at the proximal and distal ends of the stack are 0.6 m in diameter and 0.8 m in length; mid-stack cells are slightly shorter. A typical three or four cell stack is 2 m in length. Small mesosome-like inclusions in the distal cell are involved in the development of droplet shaped cells which are released from the end of each stack. These specialised droplet cells probably transfer to new hosts when C. weissei cells collide, thereafter developing into new epibiont stacks. It is likely that the epibiont grows heterotrophically using the substantial production of dissolved organic carbon within the dense plates of photosynthesising C. weissei which develop naturally. Thus the epibiont uses its unusual method of growth and dispersion to maintain position in the microbial plate upon which it depends.     

Water stress-induced oxidative damage and antioxidant responses in micropropagated banana plantlets

Oxidative injury and antioxidant responses were investigated in two banana genotypes (Musa AAA Berangan and Musa AA Mas) subjected to 40 % PEG-induced water stress. PEG treatment resulted in oxidative injury, as expressed in increased lipid peroxidation and reduced membrane stability index, in both cultivars; however, greater oxidative injury was detected in Mas. Under PEG treatment, catalase activity and glutathione reductase activity were enhanced in both cultivars, but were higher in Mas. Ascorbate peroxidase activity was enhanced in Berangan under water stress, but was unaffected in Mas. Meanwhile, superoxide dismutase activity was inhibited in both cultivars under water stress, but higher activity was detected in Berangan. Higher ascorbate peroxidase and superoxide dismutase activities were associated with greater protection against water stress-induced oxidative injury.     

Ultrastructure of spermatogenesis and sperm ofMulticotyle purvisi (Plathelminthes,Aspidogastrea)

Summary The ultrastructure of spermatogenesis is described for the first time in an aspidogastrean. The zone of differentiation which is usually formed during digenean spermiogenesis was not observed inMulticotyle purvisi. Instead, spermatid components are assembled within the common cytoplasmic mass before the outgrowth of spermatids. Microtubules, mitochondrion, nucleus and axonemes including their basal body regions, migrate from the cytoplasm into the spermatid which is pinched off at the level of the arching membrane. An unusual, complex structure of the basal body region is described. Intercentriolar bodies and striated rootlets are left behind and quickly disappear from the residual cytoplasm. Despite these atypical aspects, spermiogenesis results in the formation of mature sperm with the classical structure common to Digenea and Monogenea Polyopisthocotylea with the addition of some extra, non-cortical microtubules and a dense rod along part of the length of the sperm.Abbreviations used in the figures A cell type A, primary spermatogonium - AM arching membrane - AX axoneme - AZ attachment zone - B cell type B — spermatogonium - BB basal body region - C cell type C — spermatogonium - CEL central element - CI cisternae - CY cytophore - D cell type D — primary spermatocyte - DO doublet of microtubules - DR dark rod - E cell type E — multinucleate condensed cytophore - ER endoplasmic reticulum - G glycogen - GO Golgi body - I intercentriolar body - LB lamellate body - M mitochondrion - ME remnants of arching membranes - MT microtubules - N nucleus - R rootlet - S spermatid     

The “interval timer”, photoperiod and temperature in the seasonal development of parthenogenetic and sexual morphs in the lime aphid,Eucallipterus tiliae L.

Summary The ability of the lime aphid to produce sexuals (males and females) as an alternative to parthenogenetic females is regulated by a timing mechanism (interval timer) which restrains the appearance of these morphs early in the year. In this species there are two interval timers: one controls the production of sexual females, and the other controls the production of males. Both intervals timers are sensitive to day-length and temperature but they respond in different ways.With the approach of autumn the waning effect of the interval timer inhibiting female production combined with the short day-lengths results in an increasing proportion of the aphids developing into sexual females. The restraining effect of the interval timer results in a gradual transition from parthenogenetic to gamic reproduction over a period of several generations and is still operational in the autumn. However, in this species even relatively long day conditions (17 h) can induce the development of oviparae. This low threshold of response to day-length combined with the short generation time results in the sexual morphs appearing very early in the year. This is of considerable adaptive significance in years when, as frequently happens, the aphids disappear locally before the onset of autumn.     

Indignant suicide in the Pacific: an example from the Toraja highlands of Indonesia

This paper describes and analyzes a type of Toraja (South Sulawesi, Indonesia) suicide in which a person kills him or herself after having been slighted or offended, usually by a close family member. Comparing and contrasting such suicides to similar types found elsewhere in Austronesia-speaking Oceania, the paper argues that self-inflicted deaths of this nature are not so much anomic, as suggested by some analysts, as indignant; they are committed by persons who feel that they have been severely mistreated or abused according to traditional notions of reciprocity, mutual aid, and the dangers of frustrated desire. The paper concludes by suggesting that Durkheim may have underestimated the frequency and importance of indignant suicide in traditional societies and that, conversely, contemporary analysts may be underestimating the importance of traditional norms and values in accounting for the high rates of suicide found in many parts of the Pacific today.     

Monosomic analysis of heading date and spikelet number in the common wheat (Triticum aestivum L.) multispikelet line ‘Noa’

Summary Genetic analysis of heading date and spikelet number was carried out in the common wheat (Triticum aestivum L.) multispikelet line Noa, by using the monosomic series of the regular line Mara. Noa's high number of spikelets was found to be controlled by a recessive major gene on chromosome 2D; a slight reduction in spikelet number was induced by another recessive gene on Noa's 7A chromosome. Noa's late heading date was found to be controlled by two recessive genes, located on chromosome 2D (a major effect) and 6B (a minor effect). The nature of the genes located on Noa's 2D chromosome and the relationship between spikelet number and heading date are discussed.     

Osmotropotaxis inDrosophila melanogaster

Summary Drosophila melanogaster is able to perform osmotropotaxis under open-loop conditions. With an optimal stimulus the average turning tendency to the side of higher concentration corresponds to a circular track with radiusr=0.8 cm. The response amplitude does not decrease within 1 or 2 h. Unilaterally antennectomized flies in an homogeneous odor field show a permanent turning tendency towards their intact side.The smallest concentration ratio to elicit osmotropotaxis in normal flies ranges between 610 and 910 at high and between 210 and 510 at an about 50 times lower odor intensity. No negative tropotaxis (i.e. turning to the side of lower concentration) is observed, even with strong repellents.     

Identification of quantitative trait loci (QTLs) for heading date and plant height in cultivated rice (Oryza sativa L.)

Lemont and Teqing are both semidwarf rice varieties that differ in heading date by only 6 days. However, when Lemont and Teqing are crossed there is transgressive segregation for both heading date (HD) and plant height (PH). By testing 2418 F₄ lines with 113 well-distributed RFLP markers, we identified and mapped chromosomal regions that were largely responsible for this transgressive segregation. QHd3a, a QTL from Lemont that gives 8 days earlier heading, was identified on chromosome 3 approximately 3 cM from the marker RG348. Another QTL with a large effect, QHd8a, which gives 7 days earlier heading, was identified on chromosome 8 of Teqing between RG20 and RG1034. Along with a QTL, QHd9a with a phenotypic effect of 3.5 days, these genomic regions collectively explain 76.5% of the observed phenotypic variance in heading date. Four QTLs which altered plant height from 4 to 7 cm were also mapped; these collectively explain 48.8% of the observed phenotypic variation in plant height. None of the QTLs for plant height mapped to chromosome 1, the location of the semidwarf gene sd-1. All three of the HD loci mapped to approximately the same genomic locations as PH QTLs, and in all cases, there was a reduction in height of approximately 1 cm for every day of earlier heading. The correspondence between the HD and some of the PH loci suggests that genes at these chromosome locations may have pleiotropic effects on both HD and PH. The observed heterosis in the F₁ plants for HD can be largely explained by the dominance for earliness of the identified HD loci and distribution of earlier heading alleles in the parents. However, overdominance observed at one of the PH QTL may, at least in part, be responsible for the observed heterosis in PH.     

Identification of a cDNA encoding a plant Lewis-type alpha1,4-fucosyltransferase

Recently, it has been found that plants, including tomato (Lycopersicon esculentum), express the Lewis-a epitope, Gal1,3(Fuc1,4)GlcNAc, on some N-glycans. By searching the EST database, it was possible to identify a tomato cDNA encoding a protein, designated FucTC, of 413 amino acids with homology to plant and mammalian 1,3/4-fucosyltransferases. The cDNA was expressed in Pichia pastoris and the recombinant enzyme was found to transfer fucose from GDP-Fuc (K_m 16 M) to lacto-N-tetraose (Gal1,3GlcNAc1,3Gal1,4Glc; K_m 80 M) as well as to 1,3- and 1,4-galactosylated N-glycans. It is concluded that FucTC is responsible for the biosynthesis of Lewis-a on N-glycans in tomato.