Northwestern Argentina: A Center of Genetic Diversity of Lemon Verbena (Aloysia citriodora Paláu,Verbenaceae)

The aerial parts of lemon verbena (Aloysia citriodora Paláu ) are worldwide used due to their medicinal and aromatic properties. The essential‐oil and acteoside contents have been proposed as the main quality markers for their pharmacological and organoleptic features. The northwestern region of Argentina has been repeatedly proposed as the place of origin for this species. For this reason, the essential‐oil yields and chemical compositions of leaves of 25 populations of lemon verbena from both wild collections and experimental crops from this region were studied. Plants from six different collections were subsequently grown on the same experimental parcel located at Cerrillos, Salta province, during more than seven years. In addition, the acteoside contents determined in all the samples collected in 2010 showed significant variations (from 0.5 to 4.0%). Large differences were observed in the essential‐oil composition and yields, which ranged from 0.4 to 2.1% (v/w). Nevertheless, most of the samples complied with the European Pharmacopoeia specifications. A remarkable chemical diversity with at least four clearly defined chemotypes was detected in this region. Therefore, it would be urgent to encourage actions to protect these genotypes of lemon verbena in the northwestern Argentina.     

Endo-polygalacturonase production from untreated lemon peel byAspergillus sp. CH-Y-1043

Summary Endo-polygalacturonase (endo-PG) production byAspergillus sp. CH-Y-1043 using untreated lemon peel as the sole carbon source was investigated. This strain was observed to produce more activity of endo-PG at 37°C than at 29°C. Untreated lemon peel proved to be a beeter substrate than citrus pectin for endo-PG production. Modification of the culture medium and lowering of the initial pH to 2.8 caused a 10-fold increase in the production of endo-PG activity using lemon peel.     

Mitochondrial DNA polymorphism induced by protoplast fusion in Cruciferae

Summary The mitochondrial genomes of five rapeseed somatic hybrid plants, which combine in a first experimentBrassica napus chloroplasts and a cytoplasmic male sterility trait coming fromRaphanus sativus, and in a second experiment chloroplasts of a triazine resistantB. compestris and a cytoplasmic male sterility trait fromR. sativus, were analyzed by restriction endonucleases. Restriction fragment patterns indicate that these genomes differ from each other and from both parents. The presence of new bands in the somatic hybrid mitochondrial DNA restriction patterns is evidence of mitochondrial recombination in somatic hybrid cells. In both parental and somatic hybrid plants large quantitative variations in a mitochondrial plasmid-like DNA have been observed. Our results suggest that the cytoplasmic support for male sterility is located in the chromosomal mitochondrial DNA instead of the plasmid-like DNA.     

Caprellids (Crustacea: Amphipoda) from Papua New Guinea,with the description of a new species

This is the first study of caprellid amphipods from the coast of Papua New Guinea. Several collections from Madang Lagoon (north) and Bootless Bay (south) have been studied. Seven species in seven genera are recorded, of which Pseudoproto papua sp. nov. is described as new to science. The genus Pseudoproto Mayer, 1903 has consisted, so far, of only one species, Pseudoproto fallax Mayer, 1903. Although only a single male has been found of Pseudoproto papua sp. nov., differences in antennae, mouthparts, gnathopod 2 and pereopods 3 and 4 have revealed that it represents a new species of Pseudoproto. Lateral view figures of all species, together with a key to species level for the Caprellidea from Papua New Guinea are also included. Communicated by H.-D. Franke     

Vitellogenetic defects in hybrids of the species pair Drosophila virilis and Drosophila texana

In interspecific matings between the species Drosophila virilis and Drosophila texana, female sterility can be observed in F₂ backcross females and in F₂ hybrid females. The results presented in this report show that the female sterility, whenever it exists, is due to prevention of vitellogenin synthesis in the fat body, but other abnormalities such as defects with the hybrid ovaries are not excluded. The observation that sterility appears among females from backcrosses suggests that incompatibilities between interspecific genes may cause female sterility even in the presence of a complete habloid genome from one or the other species. Yet, the parallel observation that female sterility appears only in hybrid females with recombinant chromosomes indicates that sterility results when conspecific combinations of genes on the same chromosome are broken by interspecific recombination. © 1996 Wiley-Liss, Inc.     

Patulin and aflatoxin in brown rot lesion of apple fruits and their regulation

Aspergillus flavus, A. niger, Penicillium expansum and Rhizopus stolonifer were the most frequently isolated fungi from healthy apple fruits. Alternaria alternata was the most common organism of rotten apple fruits, followed by A. niger, A. flavus, P. expansum and R. stolonifer. The prevalent type of decay, brown rot lesion, is caused by R. stolonifer followed by A. flavus, A. niger, A. alternata and P. expansum. Sodium hypochlorite had good curative properties against fruit rots. The main natural mycotoxins produced in rotten apple were patulin and aflatoxins. The optimum temperature for patulin production by P. expansum was 15 °C after 15 days. Complete inhibition of patulin formation was attained using 0.2% lemon oil and > 90% inhibition using 0.05% lemon and 0.2% orange oils. Also significant inhibition (> 90%) of aflatoxin production was observed with 0.2% lemon oil. This revised version was published online in July 2006 with corrections to the Cover Date.     

Speciation and reduced hybrid female fertility in house mice

In mammals, intrinsic postzygotic isolation has been well studied in males but has been less studied in females, despite the fact that female gametogenesis and pregnancy provide arenas for hybrid sterility or inviability that are absent in males. Here, we asked whether inviability or sterility is observed in female hybrids of Mus musculus domesticus and M. m. musculus, taxa which hybridize in nature and for which male sterility has been well characterized. We looked for parent‐of‐origin growth phenotypes by measuring adult body weights in F1 hybrids. We evaluated hybrid female fertility by crossing F1 females to a tester male and comparing multiple reproductive parameters between intrasubspecific controls and intersubspecific hybrids. Hybrid females showed no evidence of parent‐of‐origin overgrowth or undergrowth, providing no evidence for reduced viability. However, hybrid females had smaller litter sizes, reduced embryo survival, fewer ovulations, and fewer small follicles relative to controls. Significant variation in reproductive parameters was seen among different hybrid genotypes, suggesting that hybrid incompatibilities are polymorphic within subspecies. Differences in reproductive phenotypes in reciprocal genotypes were observed and are consistent with cyto‐nuclear incompatibilities or incompatibilities involving genomic imprinting. These findings highlight the potential importance of reduced hybrid female fertility in the early stages of speciation.     

DISSECTING THE GENETIC ARCHITECTURE OF F1 HYBRID STERILITY IN HOUSE MICE

Hybrid sterility as a postzygotic reproductive isolation mechanism has been studied for over 80 years, yet the first identifications of hybrid sterility genes in Drosophila and mouse are quite recent. To study the genetic architecture of F₁ hybrid sterility between young subspecies of house mouse Mus m. domesticus and M. m. musculus, we conducted QTL analysis of a backcross between inbred strains representing these two subspecies and probed the role of individual chromosomes in hybrid sterility using the intersubspecific chromosome substitution strains. We provide direct evidence that the asymmetry in male infertility between reciprocal crosses is conferred by the middle region of M. m. musculus Chr X, thus excluding other potential candidates such as Y, imprinted genes, and mitochondrial DNA. QTL analysis identified strong hybrid sterility loci on Chr 17 and Chr X and predicted a set of interchangeable autosomal loci, a subset of which is sufficient to activate the Dobzhansky–Muller incompatibility of the strong loci. Overall, our results indicate the oligogenic nature of F₁ hybrid sterility, which should be amenable to reconstruction by proper combination of chromosome substitution strains. Such a prefabricated model system should help to uncover the gene networks and molecular mechanisms underlying hybrid sterility.     

Plastid DNA diversity in natural populations of Beta maritima showing additional variation in sexual phenotype and mitochondrial DNA

Summary Plants of two natural populations of Beta maritima, characterized by high percentages of male-sterile plants, have been investigated for organelle DNA polymorphism. We confirm the two classes of mitochondrial DNA variation previously described: (i) mitochondrial DNA (mtDNA) type N is associated with male fertility, whereas mtDNA type S can cause cytoplasmic male sterility (CMS); (ii) the 10.4-kb linear plasmid is observed in both types of mitochondria and is not correlated with the cytoplasmic male sterility occurring in this plant material. A third polymorphism is now described for chloroplast DNA (ctDNA). This polymorphism occurs within single populations of Beta maritima. Three different ctDNA types have been identified by HindIII restriction analysis. Among the plants studied, ctDNA type 1 is associated with N mitochondria and type 2 with S mitochondria. Chloroplast DNA type 3 has been found both in a fertile N plant and in a sterile S plant. This finding suggests that the chloroplast DNA polymorphism reported is not involved in the expression of male sterility. A comparison with Beta vulgaris indicates that ctDNA type 3 of Beta maritima corresponds to the ctDNA of fertile sugar beet maintainer lines. The three types of Beta maritima ctDNA described in this study differ from the ctDNA of male-sterile sugar beet.     

Mitochondrially-targeted expression of a cytoplasmic male sterility-associated <Emphasis Type="Italic">orf220</Emphasis> gene causes male sterility in <Emphasis Type="Italic">Brassica juncea</Emphasis>

Background  

The novel chimeric open reading frame (orf) resulting from the rearrangement of a mitochondrial genome is generally thought to be a causal factor in the occurrence of cytoplasmic male sterility (CMS). Both positive and negative correlations have been found between CMS-associated orfs and the occurrence of CMS when CMS-associated orfs were expressed and targeted at mitochondria. Some orfs cause male sterility or semi-sterility, while some do not. Little is currently known about how mitochondrial factor regulates the expression of the nuclear genes involved in male sterility. The purpose of this study was to investigate the biological function of a candidate CMS-associated orf220 gene, newly isolated from cytoplasmic male-sterile stem mustard, and show how mitochondrial retrograde regulated nuclear gene expression is related to male sterility.     

Effects of large-scale anthropogenic development on juvenile lemon shark (Negaprion brevirostris) populations of Bimini, Bahamas

The waters around Bimini (25° 43.70′ N, 79° 18.00′ W) provide an ideal nursery location for juvenile lemon sharks, Negaprion brevirostris, but this habitat is threatened by the development of a large resort. Since 1999 the North Sound (NS) has been subjected to intermittent periods of dredging, the most intensive of which was in March 2001. Possible effects from the development up to June 2006 were investigated by: comparing growth rates of juvenile lemon sharks in the NS, Sharkland (SL) and South Bimini (SB) nurseries between 1995-2005 using before-after, control-impact (BACI) analysis; analyzing survival of juvenile lemon sharks in the NS and SL between 1995–2006; and by comparing habitat structures in the NS and SB nurseries in 2003 and 2005. BACI analysis detected no statistically significant difference between the growth rates of juvenile lemon sharks in the three nurseries before and after the impact date of March 2001. However, a reduction in the survival rate of juvenile lemon sharks in the NS after March 2001 was statistically significant, including a 23.5% decline in first-year survival. Habitat structure of the NS in 2003 and 2005 also varied with the mean percentage cover of the seagrass Thalassia testudinum declining by 17.7% since 2003. Our results indicate a correlation between the development thus far and a decline in the survival rates of juvenile lemon sharks and changes in the habitat structure of the NS. To elucidate further information regarding potential effects of the resort development on juvenile lemon sharks in the NS nursery, we suggest several future research directions.     

Allelic relationship of four male sterility genes and nucleo-cytoplasmic interactions in the expression of male sterility in pearl millet,Pennisetum americanum (L.) leeke

Summary Male sterility genes isolated in four inbred lines of pearl millet were found allelic. The differences between male fertile and male sterile phenotypes is mainly due to a single gene. Presence of a dominant gene (Ms) resulted in male fertility and double recessiveness (ms ms) in male sterility. However, genic male sterility (GMS) in Pennisetum is not a simply inherited case of monogenic recessive condition but is influenced by cytoplasmic and several nuclear factors. In a male sterile, the stage at which the male sterility gene is expressed during the development of the male gametophyte resulting in breakdown of the cells is influenced by cytoplasmic and other nuclear factors. Two types of cytoplasm, C-1 and C-2, are recognized. Presence of any two recessive male sterility alleles in C-1 led to breakdown of male development before differentiation of an archesporium in the anther (Arc-type); in C-2 cytoplasm, degeneration started during meiosis with fusion of meiocytes and syncyte formation (Syn-type), or at post-meiotic stages terminating in abortion of microspores before first pollen mitosis (PGM type). The triggering of activity of recessive male sterility genes in C-2 cytoplasm appeared to be regulated by two nuclear factors, R ₁ and R ₂ with duplicate gene action. Recessiveness for both the R factors in C-2 cytoplasm resulted in PGM-type expression. The action of R ₁ and R ₂ is specific to C-2 cytoplasm. Mutation of cytoplasm from C-1 to C-2 and C-2 to C-1 was observed.     

Infection Biology of Bacterial Wilt of Forage Grasses

Infection of perennial ryegrass (Lolium perenne L.), Italian ryegrass (Loliummultiflorum L.), and timothy (Phleum pratense L.) by Xanthomonas campestris pv. graminis and Xanthomonas campestris pv. phlei occurred mainly via wounds rather than natural openings. Nevertheless, bacteria were detected by isolation and immunofluorescence in plants sprayed with the pathogen without prior wounding and in plants in which intact ears had been dipped in inocula. High concentrations of bacteria were observed around the stomata of perennial ryegrass and timothy by scanning electron microscopy 48 h after inoculation. Perennial ryegrass and Italian ryegrass and individual plants of ryegrass and timothy differedin susceptibility to the pathogens.     

Identification of neutral alleles at pollen sterility gene loci of cultivated rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) from wild rice (<Emphasis Type="Italic">O. rufipogon</Emphasis> Griff.)

Oryza rufipogon Griff. is the ancestor of Asian cultivated rice (O. sativa L.) and possesses valuable genes for rice breeding. Pollen abortion is one of the major causes of indica–japonica hybrid sterility in rice and it happens due to allelic interaction at the pollen sterility gene loci. A total of six loci (Sa, Sb, Sc, Sd, Se, and Sf) have been found to be associated with F₁ pollen sterility between indica and japonica rice, and five of them (all except Sf) have been mapped. Neutral alleles (S ⁿ ) at each locus have the potential to overcome the pollen sterility associated with the respective locus. Therefore, exploitation and utilization of neutral alleles have significant importance in overcoming indica–japonica hybrid sterility. In this study, an accession (IRW28) of O. rufipogon, native to China, was selected as paternal to cross with typical japonica (Taichung 65) and indica (Guanglu’ai 4) tester lines, and two F₂ populations were developed. The simple sequence repeat markers tightly linked to five pollen sterility loci were applied for genotyping the F₂ populations. Chi-squared tests were applied to examine the normal segregation/distortion at each locus. The expected and observed pollen sterility for each locus were estimated. As a result, the genotypes at five pollen sterility gene loci for IRW28 were identified as: Sa ⁱ⁻¹/Sa ⁱ⁻¹, Sb ⁿ /Sb ⁿ , Sc ⁱ⁻²/Sc ⁱ⁻², Sd ⁿ /Sd ⁿ and Se ⁿ /Se ⁿ . Our results suggest that IRW28 (O. rufipogon) has the neutral alleles for pollen fertility at the Sb, Sd and Se loci, and these alleles have a good affinity with indica and japonica rice. These neutral alleles provide valuable gene resources to overcome the inter-subspecific hybrid pollen sterility in rice.     

Effects of extracts of Alnus glutinosa seeds on growth of Frankia strain ArI3 under static and fermentor culture conditions

The amount of root mortality caused by root pathogens such as Phytophthora nicotianae (syn. Phytophthora parasitica) has typically been inferred from the net change in root length density in sequential soil cores. Because such measurements give information only on net changes in root populations, the actual rate of root turnover is often underestimated. We used minirhizotrons to track the fate of a large number of individual fine roots of mature field-grown citrus trees over a 6-month period. This method enabled us to examine the effect of P. nicotianae population levels on fine-root mortality. Seasonal and genotypic variation in patterns of citrus fine root mortality were associated with variation in population levels of P. nicotianae. Fine root lifespans were shorter when populations of P. nicotianae were high. Fine roots of the Phytophthora-susceptible rootstock, rough lemon (Citrus jamibhiri), had shorter median lifespans and supported larger populations of P. nicotianae than the fine roots of the more tolerant rootstock, Volkamer lemon (Citrus volkameriana). Rates of root mortality were either relatively constant for roots of all ages, or increased with age; the latter pattern was most pronounced for Volkamer lemon roots. Differences in the age-dependence of root mortality may, therefore, play a role in genotypic differences in tolerance of Phytophthora root rot by these two rootstocks. H Lambers Section editor     

Comparative sensitivity of 'Prior Lisbon' lemon and 'Valencia' orange trees to foliar sodium and chloride concentrations

Abstract While citrus rootstocks differ in capacity for sodium and chloride ion exclusion, citrus scion species also vary in foliar sensitivity to NaCl salinisation. Of two common scions, ‘Lisbon’ lemon appears more sensitive, whereas ‘Valencia’ orange in less sensitive to leaf salt. In an attempt to explain this difference. ‘Valencia’ orange (Citrus sinensis [L.] Osbeck) and ‘Prior Lisbon’ lemon (Citrus limon [L.] Burm. F.) were budded to rootstocks known to differ in their ability to exclude sodium ions viz, the strong excluder Trifoliata (Poncirus trifoliata [L.] Raf.), and the weaker excluder Troyer citrange (C. sinensis×P. trifoliata); neither rootstock shows strong exclusion of chloride ions. Budded trees were held under a photosynthetic photon flux density of 450 μmol m ² S ¹ and watered with nutrient solution containing either 0 or 50 mol m ³ NaCl. Growth and photosynthetic responses were measured over 58 d following onset of salinization: salinity effects on leaf gas exchange were studied in relation to changes in leaf water status, compatible solutes and foliar content of sodium and chloride ions, over that same period. Once root-zone salinization began to influence leaf solutes (day 30 onwards), lemon showed a steeper increase in leaf chloride than occurred for orange. Although rootstock differences were without effect on this ingress of chloride ions for either scion, sodium ions were excluded from both scions to a larger extent by Trifoliata than by Troyer citrange. Carbon dioxide assimilation of scion foliage was reduced earlier and to a much larger extent by rootzone salinization in lemon than in orange. Furthermore, comparisons of CO₂ assimilation in relation to leaf tissue solutes between scions (on either rootstock) showed stronger responses for both sodium and chloride ions in lemon than in orange. Faster ingress of chloride into lemon leaves was identified as the crucial factor which predisposed towards expression of that contrast between scions. Although contrasts between scions in photosynthetic responses to salinization matched a faster ingress of chloride into lemon than into orange leaves, the sharper photosynthetic response of ‘Prior Lisbon’ lemon to salinity was not solely attributable to higher concentrations of chloride ions (cell sap basis). A difference between species in subcellular compartmentation of the chloride ion under saline conditions was invoked.     

Variation of sterility and fertility in Utricularia australis f. australis in Hokkaido, northern Japan

Seed-production ability was studied in Utricularia australis R. Br. f. australis Komiya and Shibata through field observation, pollination experiment, pollen culture, and isozyme analysis for populations in various regions of Hokkaido, northern Japan. Utricularia australis f. australis has previously been postulated to be sterile in Japan, however, in the present study, fertile populations were found in eastern Hokkaido. Bisexual sterility and male sterility were suspected to be present in populations in the western part of Hokkaido. There was also a strain that seemed to produce no seed because of intra-clonal inbreeding depression or self-incompatibility. Isozyme analysis of three enzyme systems indicated a uniformity of multienzymatic phenotype (MEP) in each population or region. The MEP grouping of populations corresponded to the type of sterility and fertility revealed by pollination and pollen culture experiments. These experiments suggested that each regional strain had its own sterility or fertility type.