Free-living plathelminthes in sheep-grazed and ungrazed supralittoral salt marshes of the North Sea: Abundance,biomass, and their significance in food chains

The supralittoral salt marshes of the North Sea are marked by high halophyte primary productivity. The environmental factors are strongly fluctuating. Despite these features the metazoan meiofaunal abundance is equal to that found in other littoral habitats. On average 1250 marine metazoans are found per 10 cm² in ungrazed and 770 per 10 cm² in sheep-grazed supralittoral salt marshes. Nematoda dominate in numerical abundance, Oligochaeta in biomass. Plathelminthes account for 15% of marine metazoans in ungrazed and 5% in grazed salt marshes.Total plathelminth abundance increases with halophyte density, whereas the abundance of diatom-feeding Plathelminthes decreases. In ungrazed marshes on average 104 Plathelminthes are found per 10 cm², accounting for a biomass of 0.65 g DW·m⁻². In sheep-grazed marshes the average abundance is only 32 individuals per 10 cm², accounting for a biomass of 0.1 g DW·m⁻². Average individual weight is 3.2 μg DW or 2.5 μg AFDW.In grazed salt marshes, 30% of plathelminthes feed on diatoms, 66% are predators, and 4% feed on bacteria (gut analysis). In ungrazed salt marshes only 3% are diatom-feeders, and 90% are predators feeding on Nematoda, Copepoda, Oligochaeta, and smaller Plathelminthes. Presumably plathelminthes are top predators on the salt marsh meiofauna.     

The influence of environmental conditions on settlement,distribution and growth of 0-group sole (Solea solea (L.)) in a macrotidal estuary (Vilaine,France)

In the Vilaine estuary, the environmental conditions at the onset of the settlement of metamorphosing sole have been surveyed for 5 years. The inshore migration occurs either in early or in late April depending on the hydroclimatic conditions: sole are observed in the estuary when bottom water salinity varies between 25 and 30 S and water temperature is up to 11°C. During spring, their distribution pattern is similar in all years: first, accumulation at the entrance of the estuary, then concentration in the upper parts and finally, colonization of the whole estuarine area by juveniles. Interannual variations in growth rates were observed during their first estuarine phase, in particular when the estuary is transformed into a ‘ria’ with high water temperature and salinity. These biological features are discussed according to ontogenic changes occurring during these early life stages. From field and experimental data and from literature information on sole and other pleuronectiform species, a conceptual model on relationships between environmental parameters and metamorphosis processes in estuarine areas is proposed.     

Phytoplankton biomass and potential nutrient limitation of phytoplankton development in the southeastern North Sea in spring 1985 and 1986

The vernal phytoplankton bloom was observed during cruises to the southeastern part of the North Sea (east of 6°20' E, south of 56°50'N) in 1985 and 1986. Maximum phytoplankton biomass expressed as phytoplankton carbon was similar in both years (14.5 and 17 g PPCm⁻² respectively). In 1985 the bloom was located in the less saline coastal water close to the North Frisian coast. Phytoplankton was dominated by Coscinodiscus concinnus and Thalassiosira nordenskiöldii. In 1986, highest phytoplankton biomass was observed northwest of the island of Sylt, where Thalassiosira nordenskiöldii was the dominant phytoplankton species. Within the areas of high phytoplankton standing stock, concentrations of the inorganic dissolved nutrients phosphate and silicate had dropped to nearly undetectable concentrations, whereas both in 1985 and 1986 the water was still rich (10 – 20 μM.dm⁻³) in inorganic nitrogen (DIN). This, as well as the high ratios of DIN:PO₄ and DIN:Si(OH)₄ (> 50) point to phosphate and silicate as potential limiting nutrients during the spring phytoplankton bloom. The ratios of total nitrogen (TN) to total phosphorous (TP) (> 30) indicate also that phosphorous might then be in short supply. Phosphate and silicate have to be considered as potentially limiting nutrients during the vernal plankton bloom in the coastal waters of the southeastern North Sea, with nitrogen being present in surplus at that time of the year. However, in the more offshore areas nitrogen may be considered the potentially limiting element at the same time.     

Oxygen regime,respiratory activity and biomass of microorganisms,and the carbon budget in the Fladen Ground area (Northern North Sea) during spring

A watermass, on the Fladen Grounds, marked with a drifting buoy, was studied daily during one month in spring. Hydrographic parameters, nutrient regime, oxygen regime, biomass of microorganisms and respiratory activity were determined; the high variability of the observations is discussed. From these observations, and earlier publications on the same cruise, a carbon budget is calculated. From oxygen flux calculations it appeared that the net ecosystem production must be more than 2.5 g C m⁻².d⁻¹ which could not be verified by C-14 primary production measurements. Presumably high variability in the system in time and space makes it impossible to get a fitting budget.     

Hybrid breeding for biomass yield in winter triticale: I. Hybrid performance,trait correlations and heterosis

Triticale (×Triticosecale Wittmack) holds great potential as a source for biomass production for industrial applications in Central Europe and hybrid breeding in particular appears promising owing to the higher vigour of hybrids compared to lines. In this study, a set of 178 winter triticale genotypes, including 91 hybrids, their 10 male and 23 female parental lines, as well as 54 varieties were evaluated for biomass yield and other agronomically relevant traits in 2 years at five locations in Germany. We observed a large variation of dry biomass yield as well as significant genotypic variances and high heritabilities for all traits. For the hybrids, a moderate correlation was observed between biomass and plant height and between biomass and grain yield. Mid‐parent heterosis of biomass yield ranged from ?13.6 to 16.5% with an average of 4.8%, and the maximum commercial heterosis was 9.1%. Taken together, our results illustrate the potential of hybrid breeding of triticale for biomass yield to diversify our portfolio of crops for biomass production.     

On-farm seed priming for barley on normal,saline and saline–sodic soils in North West Frontier Province,Pakistan

“On-farm” seed priming (soaking seeds in water prior to sowing) has been shown effective in producing earlier germination, better establishment and increased yields in a range of crops in many diverse environments. We carried out microplot, on-station and on-farm field experiments and participatory trials in several environments, including saline, saline–sodic and normal (non-saline, non-sodic) soils, in the North West Frontier Province (NWFP) of Pakistan over a number of years to assess the effect of priming on barley yields. In general, priming was found to increase yields of both grain and straw (an important product in NWFP agriculture). Grain yield increases due to priming were up to 53% in the participatory trials. Optimum duration of priming was between 12 and 16 h, and the response to priming was better in low potential environments than under better conditions. Priming was also more advantageous on saline–sodic than on saline soils, possibly as a result of the water content of the soil. It was concluded that “on-farm” priming of barley could be recommended to farmers in NWFP and in similar environments in other parts of the world who produce barley both for grain and for fodder.     

Variation of <Emphasis Type="Italic">Wx</Emphasis> microsatellite allele,waxy allele distribution and differentiation of chloroplast DNA in a collection of Thai rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Eighty-two varieties of rice from different regions in Thailand were selected to explore the Waxy (Wx)gene diversity and indica-japonica differentiation of chloroplast DNA. A comparison of the 5 splice site in the first intron was made between glutinous and nonglutinous rice. It revealed that non-glutinous with low-amylose content and glutinous rice were characterized as the Wx^b allele based on the G-to-T base substitution, whereas non-glutinous rice with intermediate and high amylose carried the Wx^a allele. Four Wx microsatellite alleles, (CT)_n repeat, (n = 16,17,18 and 19) were found in glutinous rice. In contrast, non-glutinous rice showed five Wx microsatellite alleles (n = 11, 16, 17, 18 and 19). The (CT)₁₇ allele was prominent allele in Thai population, while the (CT)₁₁ allele was found only in intermediate and high amylose rice varieties from southern Thailand. Almost all of upland rice grown by various ethnic groups in northern Thailand were characterized as japonica type based on their having the PstI-12 fragment in their cpDNA, whereas most of rainfed lowland varieties from other regions of Thailand were indica. This exploration of DNA-based genetic markers is important, as it enhances our ability to describe and manipulate sources of genetic variation for rice breeding programs.     

Use of morphological,molecular markers and cytology to differentiate between closely related <Emphasis Type="Italic">Gaura coccinea,G. drummondii</Emphasis> for breeding purposes

Collection of wild species is critical to increase crop germplasm gene pools. Gaura coccinea has been identified as an important source of cold tolerance (winter hardiness) for hybridization with non-cold tolerant G. lindheimeri. Identification of species in the wild is often complicated by diagnostic, morphological characteristics that may not be present at the time of collection. G. drummondii, however, can be misidentified as G. coccinea even when using some diagnostic and quantitative traits. Therefore, additional methods of distinguishing between the species are needed. Fifteen populations of both G. coccinea and G. drummondii collected for potential breeding purposes in Texas, California, and Minnesota were used to identify species-specific molecular markers and morphological characteristics. A dendrogram based on randomly amplified polymorphic DNA (RAPD) markers separated the genotypes into two groups, G. coccinea and G. drummondii. One unique RAPD marker was identified in all G. drummondii genotypes, but absent in G. coccinea. Dendrograms based on morphological data separated genotypes into three distinct groups: G. coccinea, G. drummondii, and G. sp. (393-1). Petal/sepal lengths and leaf width were smaller in G. coccinea, while fruit/stipe lengths were smaller in both G. coccinea and genotype 393-1. Cytological analysis of G. coccinea confirmed that most populations were tetraploid (2n = 4x = 28) with one hexaploid (2n = 6x = 42) genotype from Texas (1000-1). G. drummondii were primarily tetraploid (2n = 4x = 28). Occasional triploids were found. These markers, along with screening for cold tolerance, will allow for accurate identification of G. coccinea genotypes for hybridization with G. lindheimeri.     

Mining,risk and climate resilience in the ‘other’ Pacific: Latin American lessons for the South Pacific

We suggest the value of considering Pacific Latin America and the South Pacific in relationship to each other in contexts of climate change and investment in extractive industry. The paper explores the interactions between extractive industry, climate change and environmental governance through the lenses of double exposure, double movements, resilience and risk. The first part of the paper addresses the nature and scope of investments in extractive industries in this ‘other Pacific’. The geography of these investments is changing the actual and perceived distribution of exposure and risk in the region. The nature of this risk is also being affected by climate change and its implications for the geographies of water and land‐use. Much of the contention surrounding extractive industries can be understood as conflicts over the unequal distribution of this risk, how to interpret its significance and the ways in which resilience might be enhanced to respond to it. The final section of the paper discusses the ways in which mining governance and governance for resilience converge and, on the basis of recent experiences in El Salvador, analyses the difficulties in governing extractive industry in a way that manages risk and builds resilience.     

Genetic,quantitative and microscopic evidence for fusion of haploid nuclei and growth of somatic calli in cultured <Emphasis Type="Italic">ms10</Emphasis><Superscript><Emphasis Type="Italic">35</Emphasis></Superscript> tomato anthers

In plant breeding, androgenic doubled haploids represent powerful tools to save time and resources for pure line generation. While in many species efficient protocols are known, in tomato (Solanum lycopersicum), the knowledge on the induction of androgenesis is still very scarce, and little is known about the particularities of this highly recalcitrant species. The only known method capable of yielding haploid/doubled haploid tomato plants is anther culture. However, this method has important limitations, including low efficiency of haploid induction and a low proportion of spontaneously doubled haploids. To understand these limitations better, we have analyzed the process of callus formation in anthers of tomato lines carrying the ms10 ³⁵ gene for male-sterility, using light and electron microscopy, flow cytometry and genetic analysis with morphological and molecular markers. Our results demonstrate that haploid, doubled haploid and diploid calli occur in tomato anthers, although at different frequencies. Diploid calli derived either from somatic cells or from the fusion of two genetically different haploid nuclei account for more than 90% of the total of calli produced. Somatic calli are derived from the stubs of connective tissue present in the interlocular septa of anthers. This growth is markedly increased in the ms10 ³⁵ mutants, which explains their higher callogenic rates than standard tomato lines. Together, our results reveal serious drawbacks that explain the low efficiency of anther-derived, doubled haploid production in tomato, and stress the need for alternatives towards doubled haploidy.     

A simple,rapid and reliable bioassay for evaluating seedling vigor under submergence in <Emphasis Type="Italic">indica</Emphasis> and <Emphasis Type="Italic">japonica</Emphasis> rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Submergence is a major stress causing yield losses particularly in the direct-seeded rice cultivation system and necessitates the development of a simple, rapid and reliable bioassay for a large scale screening of rice germplasms with tolerance against submergence stress. We developed two new bioassay methods that were based primarily on the seedling vigor evaluated by the ability of fast shoot elongation under submerged conditions, and compared their effectiveness with two other available methods. All four bioassay methods using cultivars of 7 indica and 6 japonica types revealed significant and consistent cultivar differences in seedling vigor under submergence and/or submergence tolerance. Japonica cultivars were more vigorous than indica cultivars, with Nipponbare being the most vigorous. The simplest test tube method showed the highest correlations to all other methods. Our results suggest that seedling vigor serves as a submergence avoidance mechanism and confers tolerance on rice seedlings to flooding during early crop establishment. A possible relationship is discussed between seedling vigor based on fast shoot elongation and submergence tolerance defined by recovery from submergence stress.     

Identification of coincident QTL for days to heading,spike length and spikelets per spike in <Emphasis Type="Italic">Lolium perenne</Emphasis> L.

Flowering time is a trait which has a major influence on the quality of forage. In addition, flowering and subsequent seed yields are important traits for seed production by grass breeders. In this study, we have identified quantitative trait loci (QTL) for flowering time and morphological traits of the flowering head in an F₁ mapping population in Lolium perenne L (perennial ryegrass), a number of which have not previously been identified in L. perenne mapping studies. QTL for days to heading (DTH) were mapped in both outdoor and glasshouse experiments, revealing three and five QTL for DTH which explained 53% and 42% of the total phenotypic variation observed, respectively. Two QTL for DTH were detected in both environments, although they had contrasting relative magnitudes in each environment. One QTL for spike length and three QTL for spikelets per spike were also identified explaining, a total of 32 and 33% of the phenotypic variance, respectively. Furthermore, the QTL for spike length and spikelets per spike generally coincided with QTL for days to heading, implying co-ordinate regulation by underlying genes. Of particular interest was a region harbouring overlapping QTL for days to heading, spike length and spikelets per spike on the top of linkage group 4, containing the major QTL for spike length identified in this population.