bluuebunny/crossref_metadata_2025 huggingface dataset:
Disentangling the effects of size-dependent encounter and susceptibility to predation with an individual-based model for fish larvae
Authors: Paradis A R , Pépin M , Pepin P
Published: April 2011

We investigated the effects of size-dependent encounter and susceptibility, the role of variation in the size distribution of predators, and the timing of prey-predator interaction during the larval phase in shaping the length frequency distribution of surviving fish larvae. These analyses based on general empirical size-dependent relationships may have broad implications in understanding larval fish cohort dynamics. We demonstrated that the formulations of encounter and susceptibility to predation counteract each other, an increased range of predator sizes reduces only slightly the evidence for size-selective mortality, and synchronous spawning and hatching events have the potential to yield strong size-selective mortality of a cohort of fish larvae. The important factors in generating size-selective mortality are either the timing of encounters between fish larvae and their predators or high mortality rates. We demonstrated a direct relationship between the potential of size-selective mortality and the overall mortality rate of the cohort. We suggest that it may be difficult to detect the effect of size-dependent processes in the field. A better understanding of the factors influencing encounter represents a critical element in extrapolating laboratory studies of predation to the field.
Influence of growth and survival costs of reproduction on Atlantic cod, Gadus morhua, population growth rate
Authors: Hutchings Jeffrey A
Published: April 2011

A stochastic, age-structured life history model was used to examine how age at maturity (theta), pre- (Zimm) and postreproductive (Zmat) mortality, and postreproductive growth rate can affect maximum reproductive rates of fish at low population size. Simulations suggest that annual (r) and per-generation (R0) metrics of population growth for Newfoundland's northern Grand Bank Atlantic cod, Gadus morhua, are primarily influenced by changes to mortality prior to and following reproduction. At observed weights at age and Zmat = 0.2, r ranged between 0.135 and 0.164 for cod maturing at between 4 and 7 years. Incremental increases in either Zimm or Zmat of 0.1 were associated with 0.03-0.05 reductions in r. To effect similar reductions, individual growth rate would have to decline by approximately one half. At observed weights at age, increases in Zmat from 0.20 to 0.45 increased the probability of negative per-generation growth from 3 to 26% for cod maturing at 4 years and from 6 to 46% for cod maturing at 7 years. Thus, even in the absence of fishing mortality, little or no population growth by Atlantic cod may not be unexpected in the presence of environmental stochasticity, particularly when accompanied by increases in mortality and declining individual growth.
Concentration of capelin (Mallotus villosus) in tidal upwelling fronts at the head of the Laurentian Channel in the St. Lawrence estuary
Authors: Marchand Caroline , Simard Yvan , Gratton Yves
Published: April 2011

In 1994 and 1995, continuous monitoring of physical characteristics and echo integration were used to detect aggregations of capelin (Mallotus villosus) in the upper water column in relation to thermal fronts and to examine the tidal dynamics in an intense upwelling area at the head of the Laurentian Channel. During the four cruises, fish aggregations were recorded for 72% of the fronts (n = 61) resulting from the periodic upwelling of cold waters. Over the tidal cycle, only a low fish biomass was detected when the cold intermediate waters (<2°C) upwelled during high tide; 90% of the 2-year-old capelin biomass was detected in water temperatures >2°C. Capelin zooplankton prey were concentrated primarily over the deep Laurentian Channel, with very small numbers being found in the shallower areas nearby, where the fronts occurred. The prey concentrations did not increase at the fronts at any phase of the tidal cycle. The few zooplankton patches detected by the optical plankton counter did not correspond to either physical structures or fish concentrations. The gut fullness index and the stomach contents of the capelin caught in fronts did not differ from those of capelin caught elsewhere. These frontal aggregations of capelin seem therefore to be driven more by a threshold response to low temperatures than by trophic interactions based on a higher prey density.
Skipper skill and panel data in fishing industries
Authors: Squires Dale , Kirkley James
Published: April 2011

Skipper skill or managerial ability plays a central role in the harvesting of fish and fishing power. Examining the influences of managerial ability on catch rates, however, may be complicated, since managerial ability is generally unobservable. Using panel data on production activities in the Pacific Coast trawl fishery, we examine the use of the fixed- and random-effects panel data models to depict managerial skill by intervessel differences, representing differences in technical efficiency. The random-effects production model is selected over the fixed-effects model. We conclude that skipper skill is more related to finding fish, dealing with unforseen events, and handling inclement weather than it is to managing the economic inputs.
Interplay between dispersal determinants of larval hydropsychid caddisflies
Authors: Holomuzki Joseph R , Pillsbury Robert W , Khandwala Sapna B
Published: April 2011

We examined the interactive effects of predator (perlid stoneflies) presence, epilithic algal cover, and substrate size on drift and resettlement decisions by larval hydropsychid caddisflies in a series of experiments conducted in real and artificial streams. Predator effects on drift-entry depended on algal structural complexity. Stoneflies significantly increased hydropsychid drift from biofilm-covered rocks but not from rocks covered with a thick periphyton mat or with a macroalga (Cladophora glomerata, approx. 20% surface cover). When we manipulated degree of Cladophora cover, we found that Cladophora even in small amounts (4-13% cover) nullified stonefly effects on drift and that drift was inversely related to amount of Cladophora on rocks. However, Cladophora may only be important as a dispersal determinant until retreats (i.e., immovable cases) are constructed and vulnerability to predators decreases. Hydropsychid drift rates were positively related to gravel abundance, but Cladophora presence enhanced settlement rates on the substrate. Our study shows that multiple factors jointly influence dispersal patterns of hydropsychid larvae and that the relative strength of any one factor as a dispersal determinant varies depending on conditions of other determinants.
Influence of large woody debris and a bankfull flood on movement of adult resident coastal cutthroat trout (Oncorhynchus clarki) during fall and winter
Authors: Harvey Bret C , Nakamoto Rodney J , White Jason L
Published: April 2011

To improve understanding of the significance of large woody debris to stream fishes, we examined the influence of woody debris on fall and winter movement by adult coastal cutthroat trout (Oncorhynchus clarki) using radiotelemetry. Fish captured in stream pools containing large woody debris moved less than fish captured in pools lacking large woody debris or other cover. Fish from pools lacking cover commonly moved to habitats with large boulders or brush, particularly during the day. Movements by fish over 1-day periods were strongly influenced by large woody debris or other elements providing cover. Fish initially found in habitats lacking large woody debris, large boulders, or brush cover moved the most extensively, while fish initially found in pools with large woody debris moved the least. Fish did not move extensively in response to a bankfull flood, although some moved to habitat downstream of large woody debris in tributaries or secondary channels. Habitat downstream of woody debris in the main channel was not used during the flood, apparently because of extreme turbulence. Overall, these observations provide additional evidence for the value of habitat complexity to some stream fishes and support previous observations of minimal effects of flooding on adult fish.
Destructive grazing, epiphytism, and disease: the dynamics of sea urchin - kelp interactions in Nova Scotia
Authors: Scheibling Robert E , Hennigar Allan W , Balch Toby
Published: April 2011

We measured the rate of advance of urchin (Strongylocentrotus droebachiensis) feeding aggregations (fronts) as they destructively grazed kelp beds (Laminaria longicruris) at both a wave-exposed site and a sheltered site in Nova Scotia over 3.5 years. The grazing fronts were composed of high densities of large adults (up to 98 and 70 per 0.25 m2at the exposed and sheltered sites, respectively). Urchins in the recently formed barrens, or in adjacent kelp beds, occurred at much lower densities and consisted mainly of juveniles. The fronts moved onshore into shallower water at each site, but their rate of advance varied markedly between sites and over time at each site, ranging from 0 to 4 m·month-1. The rate of advance of a front was related to the biomass of urchins; fronts did not advance below a threshold biomass of ~2 kg·m-2. Infestations of kelp by an epiphytic bryozoan (Membranipora membranacea) caused marked reductions in kelp canopy cover and biomass during winter, but the canopy regenerated through recruitment of juvenile sporophytes in spring. A localized outbreak of disease decimated S. droebachiensis at the exposed site in 1993, which enabled kelp to recolonize the barrens. Surviving urchins gradually reaggregated and resumed destructive grazing after ~1.5 years. A recurrence of disease in 1995 eliminated urchins at both sites and terminated the transition from kelp beds to barrens on a coastal scale. Our findings have important implications for the management of the urchin fishery, which targets grazing fronts for harvesting.
Dispersal of early life stage haddock (Melanogrammus aeglefinus) as inferred from the spatial distribution and variability in length-at-age of juveniles
Authors: Shackell Nancy L , Frank Kenneth T , Petrie Brian , Brickman David , Shore Jennifer
Published: April 2011

In southwestern Nova Scotia, haddock (Melanogrammus aeglefinus) spawning is centered on Browns Bank where the variability of a partial gyre influences the distribution of eggs and larvae. An unknown proportion of each year-class is advected northward to the Bay of Fundy. We examined the variability in length at age 2 as an index of retention during early life. We assumed that early life stages that are retained in the Scotian Shelf area grow more slowly, while those that are advected into the Bay of Fundy grow more quickly. An optimization program was used to estimate the proportions of Scotian Shelf and Bay of Fundy sized components in length at age 2 bimodal frequency distributions for year-classes 1968-1993. The median proportion of Scotian Shelf sized fish was 0.89. A physical circulation model showed that the majority of particles released on Browns Bank drifted towards the Bay of Fundy. Results of the physical model and the size-based index differ partly because the former predicts the fate of passive particles, while the latter is an integrated measure of the proportion of fish retained and surviving. Survival is associated with high wind stress (r = -0.5, p = 0.011, n = 25) implying a higher probability of survival of those retained in the Scotian Shelf region.
Factors influencing invertebrate communities in prairie wetlands: a multivariate approach
Authors: Zimmer Kyle D , Hanson Mark A , Butler Malcolm G
Published: April 2011

We examined the relationships between invertebrate community structure and a number of biotic and abiotic variables in 19 semipermanent prairie wetlands. We tested whether aquatic invertebrate communities differed (i) between wetlands with and without fathead minnows (Pimephales promelas) and (ii) according to drainage history of wetlands (restored versus natural, nondrained). We also evaluated influences of other environmental variables on invertebrate community structure, including abundance of aquatic macrophytes and amphibians and wetland depth and surface area. Invertebrate communities differed significantly between wetlands with and without fathead minnows, largely due to lower relative abundance of 19 invertebrate taxa (of 32 taxa analyzed) in wetlands with fathead minnows. In contrast, we found no differences in these taxa between natural and restored wetlands. Canonical correspondence analysis indicated that invertebrate community structure was affected by abundance of fathead minnows, abundance of aquatic macrophytes, and wetland depth, with fathead minnows the most influential variable measured. Many studies have documented the effects of fish predation on zooplankton communities, but our results show that fathead minnows in prairie wetlands affect a large number of diverse invertebrate taxa. The presence of these fish results in an invertebrate community distinctly different from that found in fishless wetlands.
The first marine biological station in Canada: 100 years of scientific research at St. Andrews
Authors: Trippel Edward A
Published: April 2011

The first marine biological station in Canada was established in St. Andrews, New Brunswick, in July 1899. The original station was a portable laboratory and was moved between various summer research sites in Atlantic Canada before a permanent station was established in St. Andrews in 1908. Early research included practical problems in the fisheries and descriptive work of coastal fauna and was performed by university researchers. Contributions to Canadian Biology, a journal founded to report the findings of the early station's researchers, in time evolved into the Canadian Journal of Fisheries and Aquatic Sciences. For the first 75 years, the station was managed as part of the Fisheries Research Board of Canada and its predecessors, and since 1979 by the Department of Fisheries and Oceans (from 1972 to 1978, two other government departments held this responsibility). Research on fisheries, the environment, oceanography, and aquaculture has dominated the station's history. July 1999 marked the 100th anniversary of marine research in St. Andrews. We celebrate and remember with pride our accomplishments and look forward to the future of conserving Canada's aquatic environment and the livelihood of Atlantic Canadians.
Relationship of wooded riparian zones and runoff potential to fish community composition in agricultural streams
Authors: Stauffer J C , Goldstein R M , Newman R M
Published: April 2011

The relationship of fish community composition to riparian cover and runoff potential was investigated in 20 streams in the agricultural Minnesota River Basin during the summer of 1997. Analysis of variance indicated significant differences in fish community composition due to both riparian cover (wooded versus open) and runoff potential (high or low). Streams with wooded riparian zones had higher index of biological integrity (IBI) scores, species richness, diversity, and percentages of benthic insectivores and herbivores than streams with open riparian zones. Streams with low runoff potential had higher IBI scores and species richness than streams with high runoff potential. The riparian cover and runoff potential interaction was marginally significant with respect to IBI scores and species richness, suggesting a weak interaction between the two factors. Although both factors were important, riparian cover influenced fish community composition more than runoff potential in these streams, indicating that local factors (close to the stream) dominated landscape- or basin-level factors.
Effects of trophic status and wetland morphology, hydroperiod, and water chemistry on mercury concentrations in fish
Authors: Snodgrass Joel W , Jagoe Charles H , Bryan, Jr. A Lawrence , Brant Heather A , Burger J
Published: April 2011

We sampled fish and selected water chemistry variables (dissolved organic carbon, sulfate, and pH) in nine southeastern depression wetlands to determine relationships among wetland morphology (surface area and maximum depth), hydrology, water chemistry, and bioaccumulation of mercury (Hg) in fishes. We concentrated on three fish species representing the range of trophic levels occupied by fish in southeastern depression wetlands. Whole-body Hg concentrations were lowest in lake chubsucker (Erimyzon sucetta), a benthic detritivore, and highest in redfin pickerel (Esox americanus americanus), a top carnivore. However, variation in Hg concentrations among wetlands was greater than variation among species. Regression analyses indicated that maximum depth and hydroperiod accounted for significant portions of variation among wetlands in standardized lake chubsucker and redfin pickerel Hg concentrations. Maximum depth and dissolved organic carbon had a negative effect on standardized Hg concentrations in mud sunfish (Acantharchus pomotis). Path analysis confirmed the results of regression analyses, with maximum depth and hydroperiod having relatively large direct negative effects on Hg concentrations. Our results suggest that leaching of Hg from sediments during the drying and reflooding cycle and binding of Hg species by dissolved organic carbon in the water column are primary factors controlling the bioavailability of Hg in southeastern depression wetlands.
Estimates of stream residence time and escapement based on capture-recapture data
Authors: Manske Micheline , Schwarz Carl J
Published: April 2011

The area-under-the-curve method is a widely used method for estimating salmon escapement. The method depends on obtaining an accurate estimate of stream residence time, or stream life. This paper develops an estimator of stream residence time based on capture-recapture data. If the capture-recapture experiment is performed on the entire population, the escapement can also be estimated using the area-under-the-curve method. Simulations showed that the stream residence estimator and the area-under-the-curve estimator provide precise estimates of stream residence and escapement, respectively. These methods were used to estimate the stream residence times and escapements of coho salmon (Oncorhynchus kisutch) in a small river on Vancouver Island in 1989 and 1990.
Effect of habitat use on PCB body burden in Hudson River striped bass (Morone saxatilis)
Authors: Zlokovitz Erik R , Secor David H
Published: April 2011

The Hudson River commercial striped bass (Morone saxatilis) fishery has been closed since 1976 due to high polychlorinated biphenyl (PCB) contamination. Accurate forecasting of PCB levels in striped bass has been confounded by high variance in contamination among individuals. We investigated the relationship between habitat use and PCB contamination in Hudson River and Long Island Sound striped bass using electron microanalysis of otolith strontium to generate time series of individual salinity habitation. Males with highly contaminated levels (mean PCB = 8.3 ppm) showed freshwater resident behavior, rarely experiencing salinities >5 ppt. Several individuals showed large habitat shifts. Shifts from brackish or marine habitats to freshwater habitats were often associated with high PCB levels. A third pattern was apparent in large females, where polyhaline/euhaline salinity habitation was associated with lower PCB levels. Total PCB body burden was inversely correlated with mean salinity encountered during the most recent growth season prior to capture. Fish with recent exposure to polyhaline salinities showed high variability in PCB body burdens (0.4-9.0 ppm), suggesting a local source of PCB contamination in the New York Harbor region.
Metal concentrations in two freshwater gastropods (Mollusca) in the St. Lawrence River and relationships with environmental contamination
Authors: Flessas Christiane , Couillard Yves , Pinel-Alloul Bernadette , St-Cyr Louise , Campbell Peter GC
Published: April 2011

This study assesses the potential use of two dominant freshwater gastropod species of the St. Lawrence River, Bithynia tentaculata (Prosobranchia) and Physa gyrina (Pulmonata), as biomonitors of metal pollution. Gastropods were collected in the littoral zone of Lake St. Louis and Lake St. Pierre, two shallow fluvial lakes of the St. Lawrence River, at sampling stations chosen to represent a metal concentration gradient in sediments. The soft body tissues of snails were analyzed for Cd, Cu, Ni, Pb, and Zn. Metal concentrations in snail tissues were related to those in macrophytes, on which the snails were collected, and in nearby sediments, where the metal ion concentrations at the water-sediment interface were estimated. There was a significant effect of age on the essential metals Cu and Zn, adults of B. tentaculata showing higher concentrations than juveniles. Significant relationships were obtained between Cd and Zn concentrations in snail tissues and those in the environment (macrophytes or the estimated free metal ion levels at the water-sediment interface). Some other relationships were also obtained with Ni, Pb, and Cu in P. gyrina. Bithynia tentaculata appears to be a promising biomonitor species, particularly for Cd and Zn.
Past trophic status and hypolimnetic anoxia during eutrophicaton and remediation of Gravenhurst Bay, Ontario: comparison of diatoms, chironomids, and historical records
Authors: Little Joanne L , Hall Roland I , Quinlan Roberto , Smol John P
Published: April 2011

Quantitative paleolimnological inferences of diatom-inferred total phosphorus and chironomid-inferred hypolimnetic oxygen levels (measured as the anoxic factor) were compared along with historical records for Gravenhurst Bay, Ontario, prior to and following sewage treatment. Water quality declined dramatically following European settlement in the mid-1800s and reached its highest inferred nutrient concentrations during the first half of the twentieth century. After treatment of sewage began in 1972, surface water total phosphorus rapidly returned to near oligotrophic conditions. Diatom assemblages reflected the period of nutrient enrichment, as well as the subsequent recovery. Chironomid assemblages exhibited trends consistent with decreased availability of dissolved oxygen to deepwater habitats since ca. 1886, with profundal taxa being largely absent since ca. 1958 when deepwater anoxia became more severe. Despite remediation efforts, Gravenhurst Bay still experiences long periods of anoxia, and chironomid assemblages have shown no sign of recovery to the improved surface water quality. We suggest that chironomid assemblages responded more strongly to changes in deepwater oxygen availability than to epilimnetic nutrient concentrations, especially during periods of pronounced hypoxia. This study demonstrates the advantages of using both chironomids and diatoms in paleolimnological assessments of eutrophication, as the indicators track changes in different lake strata.
Sediment dynamics in the fluvial lakes of the St. Lawrence River: accumulation rates and characterization of the mixed sediment layer
Authors: Carignan Richard , Lorrain Stéphane
Published: April 2011

Permanent sedimentation (210Pb and 137Cs), sediment mixed layer thicknesses, and mixing coefficients (7Be) were measured in the St. Lawrence River in order to evaluate the importance of sediment retention in the particulate matter budget and to characterize the system's resilience to changing contaminant loads. Net sediment accumulation (1 to > 18 kg·m-2·year-1) is observed at most sites deeper than 4.5 m located outside the main channels. Annual sediment retention in the lakes ranges from 1.5% (Lake St. Pierre) to 17% (Lake St. Francis) of their total load of suspended solids. 7Be profiles indicate that the average mixed layer thickness, mixed layer mass, and mixing coefficient are 3.3 ± 0.2 cm, 17.8 ± 1.7 kg·m-2, and 14.9 ± 2.8 cm2·year-1, respectively. The average depth of the long-term (approximately 5 years) mixed layer determined from the 137Cs : anthropogenic Pb ratio is 5.1 ± 0.4 cm, corresponding to 30.6 ± 4.6 kg·m-2. Because the mixing coefficient in superficial sediments is relatively high, and because annual particulate matter loading to the river is comparable with its mixed sediment inventory, the system is expected to have a rather short memory of past conditions and to recover rapidly (2-5 years) following a decrease in contaminant loading.
Prevalence of lip neoplasms of white sucker (Catostomus commersoni) in the St. Lawrence River basin
Authors: Mikaelian Igor , Lafontaine Yves de , Gagnon Pierre , Ménard Chantal , Richard Yvon , Dumont Pierre , Pelletier Lyne , Mailhot Yves , Martineau Daniel
Published: April 2011

The prevalence of lip neoplasms in populations of white sucker (Catostomus commersoni) was compared among five locations in the St. Lawrence River basin, Quebec, Canada. One site in the St. Lawrence River was monitored from May 15 to October 30 for two consecutive years (1994-1995) to study the seasonal variations in the prevalence of lip neoplasms. Other sites were sampled within a few days in October 1995 or May 1996. Lesions were found in fish from four of the five sites. The prevalence at each site varied from 0 to 41.6% and, as found in the Great Lakes, was highest in fish populations from urbanized/industrialized sites. Lip neoplams were detected almost only in fish >350 mm (total length). The prevalence was slightly higher in fish captured in the spring, but the low sample size did not permit statistical detection of this seasonal variation. There was a significant positive correlation (Spearman rs = 0.83) between fish length and the prevalence and size of lesions. The prevalence was similar between sexes, and the condition factor was significantly lower in fish with papillomas from one site only. In future studies, fish size and season of capture should be taken into account to compare the prevalence of lip neoplasms of white sucker from different sites.
Trends in wild adult steelhead (Oncorhynchus mykiss) abundance for snowmelt-driven watersheds of British Columbia in relation to freshwater discharge
Authors: Smith Barry D
Published: April 2011

Snowmelt-driven rivers of British Columbia support primarily summer-run steelhead (Oncorhynchus mykiss) that may spend up to 5 years as juveniles in freshwater. Time series analyses revealed significant negative correlations between an annual index of wild adult steelhead abundance (catch-per-angler-day, CpAD) for these rivers and summer freshwater discharge when these steelhead were juveniles. The strength of these relationships was related to latitude, with the more northerly rivers generating the strongest relationship between CpAD and freshwater discharge. Potential mechanisms by which interannual variation in freshwater discharge can modulate adult steelhead abundance include reduced juvenile mortality due to lower flow velocities during the warm summer months and to the creation of more juvenile habitat in low-velocity refuges. Alternatively, interannual variability in adult steelhead abundance is driven by variability in ocean climate of which freshwater discharge is an index. Interpretation of the data and analyses was encumbered in part by particular factors affecting CpAD as an index of abundance. However, the analyses support an interpretation that steelhead survival to adulthood might be influenced by freshwater conditions more so in northern snowmelt-driven rivers than in rainfall-driven rivers because steelhead from those rivers spend more years in freshwater as juveniles.
Low-copy microsatellite markers forPinus taedaL.
Authors: Elsik Christine G , Minihan Virginia T , Hall Sarah E , Scarpa Ann M , Williams Claire G
Published: April 2011

Eighteen low-copy and genomic microsatellite markers were tested for Mendelian inheritance and then assayed in 41 Pinus taeda L. samples drawn from five regions in the southern United States. The PCR products had multiple alleles, high levels of polymorphism, and little non-specific priming. Fifteen of the 18 markers were informative for a P. taeda three-generation RFLP (restriction fragment length polymorphism) pedigree, and a P. taeda population survey revealed three to 28 alleles per locus. The highest allele numbers and polymorphic information content (PIC) values were associated with complex repeat sequences and (or) with sequences consisting of the longer strings of perfect repeats. The abundance of low- to rare-frequency alleles also accounted for high PIC values in both types of markers. Low-copy microsatellites are useful for the large, complex pine genome, especially in the absence of entire gene sequences in public databases and with the low levels of polymorphism in markers developed from expressed sequence tags (ESTs).Key words: loblolly pine, conifers, gymnosperms, trinucleotide repeat motifs.
Molecular mapping of QTLs conferring stay-green in grain sorghum (Sorghum bicolorL. Moench)
Authors: Xu Wenwei , Subudhi Prasanta K , Crasta Oswald R , Rosenow Darrell T , Mullet John E , Nguyen Henry T
Published: April 2011

Drought resistance is of enormous importance in crop production. The identification of genetic factors involved in plant response to drought stress provides a strong foundation for improving drought tolerance. Stay-green is a drought resistance trait in sorghum (Sorghum bicolor L. Moench) that gives plants resistance to premature senescence under severe soil moisture stress during the post-flowering stage. The objective of this study was to map quantitative trait loci (QTLs) that control the stay-green and chlorophyll content in sorghum. By using a restriction fragment length polymorphism (RFLP) map, developed from a recombinant inbred line (RIL) population, we identified four stay-green QTLs, located on three linkage groups. The QTLs (Stg1 and Stg2) are on linkage group A, with the other two, Stg3 and Stg4, on linkage groups D and J, respectively. Two stay-green QTLs, Stg1 and Stg2, explaining 13-20% and 20-30% of the phenotypic variability, respectively, were consistently identified in all trials at different locations in two years. Three QTLs for chlorophyll content (Chl1, Chl2, and Chl3), explaining 25-30% of the phenotypic variability were also identified under post-flowering drought stress. All coincided with the three stay-green QTL regions (Stg1, Stg2, andStg3) accounting for 46% of the phenotypic variation. The Stg1 and Stg2 regions also contain the genes for key photosynthetic enzymes, heat shock proteins, and an abscisic acid (ABA) responsive gene. Such spatial arrangement shows that linkage group A is important for drought- and heat-stress tolerance and yield production in sorghum. High-resolution mapping and cloning of the consistent stay-green QTLs may help to develop drought-resistant hybrids and to understand the mechanism of drought-induced senescence in plants.Key words: drought tolerance, genetic mapping, post-flowering stress, restriction fragment length polymorphism.
Microsatellite DNA in peach (Prunus persica L. Batsch) and its use in fingerprinting and testing the genetic origin of cultivars
Authors: Testolin Raffaele , Marrazzo Teresa , Cipriani Guido , Quarta Roberta , Verde Ignazio , Dettori Maria Teresa , Pancaldi Marco , Sansavini Silviero
Published: April 2011

We isolated and sequenced 26 microsatellites from two genomic libraries of peach cultivar 'Redhaven', enriched for AC/GT and AG/CT repeats, respectively. For 17 of these microsatellites, it was possible to demonstrate Mendelian inheritance. Microsatellite polymorphism was assayed in 50 peach and nectarine cultivars. Of the 1300 PCRs carried out, all but two produced amplified products of the expected size. All microsatellites were polymorphic, showing 2-8 alleles per locus. Heterozygosity ranged from 0.04-0.74 (mean 0.47); the discrimination power (PD) ranged from 0.04-0.84 (mean 0.60). Cultivar heterozygosity varied greatly, with one cultivar ('Independence') being homozygous at all loci. The set of microsatellites discriminated all cultivars investigated, except several sport mutations, i.e., 'Dixitime' vs. 'Springcrest', 'Compact Redhaven' vs. 'Redhaven', and two pairs of cultivars, 'Venus' vs. 'Orion' and 'Elegant Lady' vs. 'Rome Star', whose pedigrees are controversial. We were able to analyze the paternity of several cultivars. In most cases, the parenthood was confirmed. The comparison of three long-living 'Redhaven' accessions supplied by different repositories did not provide any evidence of somatic instability of microsatellites. Hence, microsatellites, ranked according to their information content, are recommended as markers of choice for peach fingerprinting and suggestions are provided for interpreting band profiles and the correct sizing of alleles.Key words: genetics, molecular markers, paternity analysis, pedigree analysis, simple sequence repeat.
A search for diagnostic AFLP markers in Cichorium species with emphasis on endive and chicory cultivar groups
Authors: Kiers A M , Mes T HM , Meijden R van der , Bachmann K
Published: April 2011

The genus Cichorium consists of two widely cultivated species C. intybus (chicory) and C. endivia (endive) and four wild species, C. bottae, C. spinosum, C. calvum, and C. pumilum. A multivariate and an UPGMA (unweighted pair group method average) analysis based on AFLP (amplified fragment length polymorphism) markers were used to establish the genetic relationships among the species and cultivar groups of C. intybus and C. endivia. At the species level, the results correspond with previously obtained phylogenetic relationships in that C. bottae is the most divergent species, and C. intybus and C. spinosum, as well as C. endivia, C. pumilum, and C. calvum formed clusters. Based on the congruence between phylogenetic and genetic analyses, unique markers were expected for all species, however, hardly any specific marker was found except for C. bottae. The analysis of cultivar groups of C. intybus resembled the species analysis in two respects: (i) grouping of cultivars according to cultivar groups, and (ii) lack of markers unique to cultivar groups. In contrast to C. intybus, the cultivar series of C. endivia do not form distinct groups, which would reflect that crosses have been made among the various cultivar groups. The relationships among Cichorium species and cultivars will be useful for setting up a core collection of Cichorium, and stress the importance of inclusion of the wild species in the collection.Key words: Cichorium, AFLP, diagnostic markers, cultivar relationships, genetic resources.
Characterization of wheat-Thinopyrum partial amphiploids by meiotic analysis and genomic in situ hybridization
Authors: Fedak George , Chen Qin , Conner Robert L , Laroche André , Petroski René , Armstrong Ken W
Published: April 2011

A combination of genomic in situ hybridization (GISH) and meiotic pairing analysis of wheat-Thinopyrum partial amphiploids was employed to identify the genomic constitution and relationships between partial amphiploids derived from wheat and wheatgrass crosses. On the basis of similarities in the meiotic behavior and GISH patterns, the alien chromosomes of two of eight partial amphiploids, TAF46 and 'Otrastayuskaya 38', were judged to originate from Th. intermedium, whereas Th. ponticum was one of the parents of the other six partial amphiploids; PWM706, PWM206, PWM209, PWMIII, OK7211542, and Ag-wheat hybrid. Each of these partial amphiploids was found to contain a synthetic alien genome composed of different combinations of St-, J-, or Js-genome chromosomes. For relatedness of partial amphiploid lines, meiotic analysis of F1 hybrids and GISH results were generally complementary, but the latter offered greater precision in identifying constituent genomes.Key words: wheat, Thinopyrum, partial amphiploids, GISH, meiotic analysis.
Ceratotoxins: Female-specific X-linked genes from the medfly,Ceratitis capitata
Authors: Rosetto M , Filippis T de , Mandrioli M , Zacharopoulou A , Gourzi P , Manetti A GO , Marchini D , Dallai R
Published: April 2011

In this paper, we report the chromosomal localization of ceratotoxins, a gene family encoding antibacterial female-specific peptides from the mediterranean fruit fly Ceratitis capitata. The analysis of both polytene and mitotic chromosomes by in situ hybridization shows that ceratotoxins are the first case of female-specific X-linked genes from the medfly C. capitata. Southern blot analysis reveals that the ceratotoxin gene family is not specifically amplified in the female reproductive accessory glands of C. capitata.Key words: ceratotoxins, female-specific genes, Ceratitis capitata, X chromosome, in situ hybridization.
The relationship between loci for mating system and fitness-related traits inMimulus(Scrophulariaceae): A test for deleterious pleiotropy of QTLs with large effects
Authors: Lin Jing-Zhong
Published: April 2011

Loci with large phenotypic effects are generally not thought to be important in the evolution of quantitative traits because of their deleterious pleiotropic effects, yet empirical studies of such pleiotropic effects are lacking. Here I use molecular markers to test the extent of deleterious pleiotropy of quantitative trait loci (QTLs) that have large effects on mating system differences between the wild plants Mimulus guttatus and M. platycalyx (Scrophulariaceae). Six fitness-related traits, namely germination rate (GR), number of nodes (NN), number of flowers (NF), plant height (HT), above-ground biomass (WT), and flowering time (FT) were examined in a growth chamber for a backcross population between M. guttatus and M. platycalyx (with M. platycalyx as recurrent parent). Interval mapping based upon a linkage map consisting of isozyme and random amplified polymorphic DNA (RAPD) markers detected no QTL for fitness-related traits near the mating system QTLs. Single-marker analysis based upon 13 markers flanking the mating system QTLs detected three significant marker-fitness trait associations, and these associations indicate beneficial effects of mating system loci. This suggests that QTLs with large effects on mating system traits do not have significant deleterious pleiotropic effects, and that they could be important factors in adaptive evolution of Mimulus.Key words: pleiotropy, mating system, fitness, quantitative trait loci, molecular marker.
Molecular contribution to selection of intergeneric hybrids between sugarcane and the wild species Erianthus arundinaceus
Authors: Piperidis George , Christopher Mandy J , Carroll Bernie J , Berding Nils , D'Hont Angélique
Published: April 2011

Erianthus arundinaceus has great potential as a germplasm source for better ratoonability, vigour, tolerance to environmental stresses, and disease resistance in sugarcane. Many unsuccessful attempts have been made to introduce these characters into modern sugarcane cultivars. We report on significant progress made since molecular tools were implemented. Sequence-tagged PCR, revealing size variation in the 5S rDNA cluster, was performed on intact leaf tissue to identify genuine hybrids six weeks after germination. This early screening of seedlings avoids the loss of genuine hybrids due to competition with selfed progeny. Of 96 crosses made involving female Saccharum officinarum or sugarcane cultivars (Saccharum spp.) and male E. arundinaceus, 26 were fertile producing 1328 seedlings. Thirty-seven genuine hybrids were unequivocally identified but only 19 have survived. Genuine hybrids were produced from only three crosses, all involving S. officinarum as the female parent. Chromosome elimination was observed in all seven hybrids analyzed using genomic in situ hybridization (GISH). Very little cross-hybridization was observed between the genomes of the two species after GISH, confirming recent molecular studies which showed that E. arundinaceus is quite distant from the genus Saccharum. The major limitation in the introgression of E. arundinaceus resides now in the apparent sterility of the hybrids.Key words: sugarcane, Erianthus, intergeneric hybrid, genomic in situ hybridization, 5S rDNA, sequence-tagged PCR.
Coevolution of A and B genomes in allotetraploidTriticum dicoccoides
Authors: Belyayev Alexander , Raskina Olga , Korol Abraham , Nevo Eviatar
Published: April 2011

Data is presented on the coevolution of A and B genomes in allotetraploid wheat Triticum dicoccoides (2n = 4x = 28, genome AABB) obtained by genomic in situ hybridization (GISH). Probing chromosomes of T. dicoccoides with DNA from the proposed A/B diploid genome ancestors shows evidence of enriching A-genome with repetitive sequences of B-genome type. Thus, ancestral S-genome sequences have spread throughout the AB polyploid genome to a greater extent than have ancestral A-genome sequences. The substitution of part of the A-genome heterochromatin clusters by satellite DNA of the B genome is detected by using the molecular banding technique. The cause may be interlocus concerted evolution and (or) colonization. We propose that the detected high level of intergenomic invasion in old polyploids might reflect general tendencies in speciation and stabilization of the allopolyploid genome.Key words: Triticum, polyploid, evolution, genomic in situ hybridization, repetitive sequences.
Organization of highly repeated sequences in surface-spread pachytene chromosomes of rye
Authors: Cuñado N , Barrios J , Santos J L
Published: April 2011

A method of preparing two-dimensional surface spreads of plant synaptonemal complexes (SCs) associated with fluorescence in situ hybridization (FISH) has been applied to analyze the location and organization of five different highly repeated DNA sequences in rye. Our observations indicate that, depending on the type of sequence, the chromatin displays different types of organization. Telomeric sequences were seen tightly associated with the SC while other repetitive DNA sequences were found to form loops that are associated with SCs only at their bases. On the contrary, the FISH signal of a centromeric satellite had a granular appearance, reflecting that the hybridization occurs only with parts of the chromatin loops.Key words: fluorescence in situ hybridization, meiosis, repetitive DNA, rye, synaptonemal complex.
Genetic variation and relationship among and within Withania species as revealed by AFLP markers
Authors: Negi M S , Singh A , Lakshmikumaran M
Published: April 2011

Withania somnifera is an important medicinal plant, and its anticancerous properties have been attributed to various classes of withanolide compounds. The objective of the present study was to investigate the inter- and intraspecific genetic variation present in 35 individuals of W. somnifera and 5 individuals of W. coagulans using AFLP (amplified fragment length polymorphism) marker technique. The information about genetic variation determined from AFLP data for 40 individuals was employed to estimate similarity matrix value based on Jaccard's coefficient. The similarity values were further used to construct a phenetic dendrogram revealing the genetic relationships. The dendrogram generated by UPGMA (unweighted pair group method of arithmetic averages) distinguished W. somnifera from W. coagulans and formed two major clusters. These two main clusters shared a similarity coefficient of 0.3, correlating with the high level of polymorphism detected. The dendrogram further separated W. somnifera into three subclasses corresponding to Kashmiri and Nagori groups and an intermediate type. The AFLP profile of Kashmiri individuals was distinct from that of the Nagori group of plants. The intermediate genotype was distinct as it shared bands with both the Kashmiri and Nagori individuals, even though it was identified as a Kashmiri morphotype. Furthermore, the intermediate type shared a similarity coefficient of 0.8 with the Kashmiri individuals. The present work revealed low levels of variation within a population though high levels of polymorphism were detected between Nagori and Kashmiri populations. The ability of AFLP markers for efficient and rapid detection of genetic variations at the species as well as intraspecific level qualifies it as an efficient tool for estimating genetic similarity in plant species and effective management of genetic resources.Key words: Withania, AFLP, genetic variation, phenetic relationships, medicinal plant.
A maize chromosome 3 addition line of oat exhibits expression of the maize homeobox geneliguleless3and alteration of cell fates
Authors: Muehlbauer G J , Riera-Lizarazu O , Kynast R G , Martin D , Phillips R L , Rines H W
Published: April 2011

Maize chromosome addition lines of oat offer the opportunity to study maize gene expression in oat and the resulting phenotypes. Morphological examination of a maize chromosome 3 addition line of oat showed that this line exhibited several morphological abnormalities including a blade-to-sheath transformation at the midrib region of the leaf, a hook-shaped panicle, and abnormal outgrowth of aerial axillary buds. Dominant mutations in the maize liguleless3 (lg3) homeobox gene result in a blade (distal)-to-sheath (proximal) transformation at the midrib region of the leaf. Ectopic expression of the dominant mutant Lg3 allele is believed to cause the phenotype. Therefore, we suspected that the maize lg3 gene, which is located on maize chromosome 3, was involved in the phenotypes observed in the maize chromosome 3 addition line of oat. Genetic analyses of an oat BC1F2family segregating for maize chromosome 3 showed that the presence of a stable maize chromosome 3 was required for the expression of these cell fate abnormalities. RNA expression analysis of leaf sheath tissue from oat plants carrying maize chromosome 3 demonstrated that maize LG3 transcripts accumulated in oat, indicating that this expression is associated with the blade-to-sheath transformation, hook-shaped panicle and outgrowth of aerial axillary bud phenotypes. Our results demonstrate that the maize chromosome addition lines of oat are useful genetic stocks to study expression of maize genes in oat.Key words: liguleless3, homeobox, oat-maize addition line.
Identification of X chromosomal restriction fragment length polymorphism markers and their use in a gene localization study inDrosophila virilisandD.littoralis
Authors: Päällysaho Seliina , Huttunen Susanna , Hoikkala Anneli
Published: April 2011

We have identified six restriction fragment length polymorphism (RFLP) markers based on unique gene sequences on the X chromosome of Drosophila virilis and D. littoralis. The markers were localized by in situ hybridization on larval polytene chromosomes, and the conjugation of the X chromosomes of the two species was studied in salivary glands of interspecific hybrid female larvae. The gene arrangement of D. virilis and D. littoralis appeared to be very different at the proximal end of the X chromosome preventing recombination between RFLP markers located in this area. Simple quantitative trait loci (QTL) analysis showed that five of our marker genes (including nonA and Dmca1A, previously found to affect male courtship song in D. melanogaster) are linked with a gene(s) having a major effect on species differences in the male courtship song between D. virilis and D. littoralis. This shows that the song gene(s) may be located inside a large X-chromosomal inversion in D. littoralis (as previously suggested), but that it may also be located on an area between this inversion and the centromere, close to nonA and Dmca1A. Localization of this gene or gene complex will be continued with the aid of our newly identified RFLP markers by making interspecific crosses between D. virilis group species with more similar X chromosomes.Key words: restriction fragment length polymorphism (RFLP), in situ hybridization, Drosophila virilis.