Burrowing activity of the earthworms Lumbricus terrestris and Aporrectodea giardi and consequences on C transfers in soil

Two earthworms species, Lumbricus terrestris (epianecic) and Aporrectodea giardi (anecic) were incubated in microcosms with an epigeic ¹³C-labelled litter for 246 d. At the end of the experiment, different soil compartments (surface casts, walls and peripheries of burrows, and surrounding soil) were sampled for ¹³C analysis. Two-dimensional images acquired using X-ray computed tomography allowed to estimate the weight of the ‘burrow wall’ and ‘burrow periphery’ compartments which are required to establish C balance. In the case of L. terrestris, the formed structures were more C litter enriched compared to the other species. The permanent character of the burrow system could lead to a high and constant enrichment of the entire burrow system. As consequence, the percentage of C litter in the ‘burrow wall’ and ‘burrow periphery’ compartments was important in spite of their low volume. The denser system developed by A. giardi resulted in C litter dilution in the whole formed structures. The C litter enrichment decreased with the soil depth, but owing to the intensity of the burrowing activity, the C litter transfers into the ‘burrow walls’ and ‘burrow periphery’ were important and the C litter was homogeneously distributed throughout the whole column.     

Impact of plants on the microbial activity in soils with high and low levels of copper

Elevated copper (Cu) concentrations have been shown to decrease the microbial activity in soils. Plants can have beneficial effects on the biological activity of soils mainly through their root exudates. In this study we investigated the impact of various plant species with different Cu tolerance levels on the microbial activity in two soils with low (10 mg/kg) and high (180 mg/kg) copper concentrations. The soil was a Kahangi Sandy Loam. Three different plants, Agrostis capillaris ‘Parys’ tolerant for Cu, Agrostis capillaris ‘Highland’ non-tolerant and Helianthus annuus tolerant and a hyper-accumulator for Cu were used. To increase the Cu availability to plants, EDTA was added to some of the pots 20 days after sowing. The effect of Cu contamination on the biological activity of soil in the presence and absence of plant growth was evaluated by measuring the dehydrogenase activity, the microbial biomass, the basal respiration, and the potential nitrification.Results show that plants increased the microbial activity in the low Cu soil. In the high Cu soil the microbial activity seemed to be related to the plant health. With the Cu-tolerant Agrostis capillaris ‘Parys’, the microbial activity increased faster than with the other plant species. Up to 50 days after sowing, the tolerant grass Agrostis capillaris ‘Parys’ had a higher plant biomass and was much healthier than the non-tolerant grass. Later on the growth of the non-tolerant Agrostis capillaris ‘Highland’ recovered, and the microbial activity of the soil reached close to those recorded for the soil treatments with the Cu-tolerant plant species. The addition of EDTA delayed the increase in microbial activity even further. The proportion of microbial biomass carbon in the organic fraction was higher in the low Cu soil than in the high Cu soil, with ratios ranging from 1.3 to 3.3 and from 0.5 to 1.7 respectively. The basal respiration rate in the original soil was significantly lower in the high Cu soil than in the low Cu soil, and was generally increased by the presence of plants.     

Microalgal Dynamics in Batch Reactors for Municipal Wastewater Treatment Containing Dairy Sewage Water

This study investigates the microalgal community dynamics associated with changes in municipal wastewater quality and discharges from the dairy industry in central Veracruz, Mexico, using an experimental stabilization-reactors system. Thirty one species of microalgae were recorded and 15 physicochemical variables were measured daily over 25 days in pretreated water. The biomass of microalgal groups displayed significant negative correlations with biochemical oxygen demand (BOD), chemical oxygen demand (COD) and total suspend solids (TSS). Conversely, a significant positive correlation was found with dissolved oxygen, pH and nitrates. Using the Canonical Correspondence Analysis we identified an initial anaerobic phase (Phase I), characterized by high BOD, TSS and COD, ammonium and faecal coliforms. This was followed by a transition phase (Phase II), an initial aerobic phase (Phase III), when water quality improved considerably, and finally an aerobic phase (IV) with a high percent reduction in these parameters and almost complete organic load removal. The most abundant species associated with these phases were Arthrospira jenneri (Cyanophyceae) and Coccomonas sp. (Chlorophyceae) in Phase I; Polytomella sp. (Chlorophyceae) in Phase II; Polytoma tetraolare, Chlamydomonas caeca (Chlorophyceae) and some Cyanophyceae including Geitlerinema, Synechocystis, Cyanobium and Glaucospira in Phase III; Carteria sp. (Chlorophyceae), Lepocynclis ovum and Euglena clavata (Euglenophcyeae) in Phase IV. Maximum richness, diversity, and biomass levels occurred during the aerobic phase. Similar to other wastewater treatment systems the high succession rates decreased with reactor stabilization. These findings provide statistical evidence on the suitability of certain microalgae species as indicators of wastewater stabilization reactor status and effluent quality.     

Implications of seed dispersal by animals for tropical reserve management

Many tropical trees bear fruits adapted for consumption by animals, and many tropical animals depend on fruits for food for at least part of the year. The purpose of this paper is to discuss the potential importance of: (1) uneven species abundance distributions; (2) the imperative of local seed dispersal for plant recruitment; and (3) seasonality of fruit production for managing small tropical reserves. Some mutualistic seed-dispersal systems are ‘pivotal’ for forest communities. Although most species of trees produce when other fruits are readily available in the forest, others (e.g. Casearia corymbosa in Costa Rican rainforest and Virola sebifera in Panamanian rainforest) bear fruits during annual periods of fruit scarcity, and consequently maintain species of fruit-eating birds and mammals which are critical for the dispersal and ultimate recruitment of many tree species at other times of the year. The question of relative abundance presents particular problems when ‘pivotal’ plant species are rare or confined to special habitats. This paper considers ecological relationships which accelerate species loss from habitat islands over and above ‘random’ loss of ecologically independent species predicted from biogeographic theory, and suggests management methods that can reduce such excessive loss.     

Assessment of genetic diversity and phylogenetic relationships in Asparagus species related to Asparagus officinalis

Eight species of the genus Asparagus, members of the group of European species closely related to A. officinalis, were analysed using internal transcribed spacer (ITS), and expressed sequence tag-derived simple sequence repeat (EST-SSR) markers, as well as cytological observations of their hybrids, to study their phylogenetic relationships and the possibility of broadening the narrow genetic base of cultivated varieties. Phylogenetic analysis using ITS data revealed two major clades: clade I consisting of A. acutifolius and clade II (referred to in this study as the ‘officinalis group’) comprised of sequences derived from species closely related to A. officinalis; but the different species within the ‘officinalis group’ could not be clearly separated. In contrast, cluster analysis of EST-SSR marker data showed six major clades and clearly separated each population, grouping most of the genotypes from each population together. That is, EST-SSR markers were found to be more informative than ITS markers about the relationships within the ‘officinalis group’, indicating that EST-SSR markers are more useful than ITS sequences for establishing phylogenetic relationships at the intrageneric level. All the crosses carried out at the same ploidy level were successful. The high crossability, together with the regular meiotic behaviour and high pollen and seed fertility observed in the interspecific hybrids analysed, suggest relatively close relationships between the species studied. We conclude that the group of species classified in the ‘officinalis group’ are in the primary gene pool, indicating that these species could be used to increase the genetic diversity of the cultivated species. In addition, the tetraploid landrace “Morado de Huétor” could be employed as a bridge to generate new cultivated germplasm.     

The ecology of a Pythium community in relation to the epidemiology of carrot cavity spot

Carrot cavity spot (CCS) is characterised by the appearance of small sunken elliptical lesions on the tap root. It is caused by a complex of Pythium species, but the species diversity and interactions within the complex have never been studied for modelling CCS epidemics. The diversity of a pathogenic Pythium community was assessed during 3 consecutive years in a field experiment after an initial artificial soil infestation with P. violae. 1241 lesions were examined, yielding 728 Pythium isolates. Conventional microbiological methods and restriction polymorphism of the internal transcribed spacer regions of the rDNA of 209 representative Pythium isolates allowed us to identify 655 isolates as belonging to six Pythium species, including P. violae and five indigenous species (P. sulcatum, P. intermedium, P. sylvaticum/irregulare, P. coloratum, and P. ultimum). Biological traits, such as pathogenicity, optimum temperature for mycelial growth and saprophytic survival of the inoculum, explained the fluctuations in the composition of the complex over 17 successive samplings during the 3-year period, most notably the prevalence of first P. violae and then P. sulcatum. P. violae and P. sulcatum were occasionally isolated in mixture from single lesions (10.4% and 9.6%, respectively). Other species were more frequently isolated in mixture: 30.8% for P. intermedium, 33.8% for P. sylvaticum/irregulare, 42.9% for P. ultimum, and 66.7% for P. coloratum. A contingency analysis allowed us to define ‘major’ and ‘minor’ species on both pathological and ecological criteria (frequency of occurrence in the complex, pathogenicity and ability to induce lesions by themselves), and demonstrated that infection by one ‘major’ pathogen species (P. violae or P. sulcatum) is not positively correlated with the presence of a second Pythium species. The ratio between ‘observed’ and ‘expected’ mixed infection frequency under the assumption of independent infection (mir) was less than 1 for P. violae, P. sulcatum, P. intermedium, and P. sylvaticum/irregulare (P < 0.05). For all Pythium species, there was a negative linear relationship between mir and pathogenicity (R² = 0.638): the less a Pythium species was pathogenic on carrot, the more often it was isolated from a CCS lesion in mixture with at least one other species. The non-significance of interactions between species during the infection phase suggests that CCS epidemics can be analysed as if they were caused by a single Pythium species.     

The triparental triploid onion <Emphasis Type="Italic">Allium</Emphasis> × <Emphasis Type="Italic">cornutum</Emphasis> Clementi ex Visiani, 1842, possesses a sterile S-type of cytoplasm

Triploid onion, Allium × cornutum Clementi ex Visiani, 1842 (2n = 3x = 24), a vegetatively reproduced garden crop, possess a complex triparental genome organization with three putative parental species, A. cepa L., A. pskemense B. Fedtsch., and A. roylei Stearn. Two of its most studied clones are the Croatian ‘Ljutika’ and the Indian ‘Pran’, which are genetically highly similar. Earlier studies have shown that ‘Pran’ possesses some molecular markers in the chloroplast DNA (cpDNA) identical to those of the unique male-sterile (S) cytoplasm, used for onion breeding. To find out whether ‘Ljutika’ also possesses a S-type of cytoplasm, we analyzed several cpDNA and mitochondrial (mtDNA) molecular markers. The PCR amplification and RFLP analysis of the chloroplast genes accD, atpF, petB and the mitochondrial gene cob, as well as the sequence analysis of the chloroplast matK and atpB-rbcL regions showed that ‘Ljutika’ possesses the male-sterile S-type of cytoplasm. The phylogenetic analysis of the matK and atpB-rbcL sequences of A. × cornutum, its parental species and other Allium species of the section Cepa showed that none of the analyzed species had the identical type of cpDNA as A. × cornutum. Results also suggested that A. pskemense can be excluded as a donor of the S-cytoplasm and a female parent, whereas cpDNA of A. roylei, although not identical to S-cytoplasm, possessed many polymorphisms of S-type. Fluorescent in situ hybridization, using fluorescently labelled parental genomic DNAs as probes in combination with fluorescently labelled 5S and 35S rDNAs enabled simultaneous visualization of the three genomes during meiosis and confirmed their homeologus intergenomic pairing.     

Rapid and sensitive determination of nitrate in plant tissue using flow injection analysis

Abstract

The determination of nitrate in waters and soil extracts by the reduction of nitrate to nitrite by metallic or liquid reductants followed by the colorimetric determination of NO₂ ^‐using the Griess‐Ilosvay reaction has been automated for use with air‐segmented auto‐analyzers or flow injection techniques. However, this technique is not applicable to plant extracts as organic species in the extracts inactivate the reduction columns. The objective of this study was to develop an automated procedure that would allow the determination of NO₃ ^‐in plant extracts without the necessity of prior manual treatment. A flow injection technique was developed that successively traps and releases NO₃in an anion exchange column thereby removing pigments and other non‐ionic and cationic species that otherwise interfere with conversion of NO₃ ^‐ to NO₂ ^‐on a copperized cadmium column. This reduction step is subsequently followed by standard Griess‐Ilosvay colorimetric detection of this ion at a wavelength of 530 nm. The technique uses relatively simple and inexpensive equipment, principally a spectrophotometer equipped with a flow‐through cell and a pen recorder output, a 6‐channel peristaltic pump with accompanying tubing and a Perspex injector/commutator valve made in a laboratory workshop. The technique was found to avoid any significant interference of pigments or other organic compounds in the plant extracts, and the results compared favorably with those obtained using the manual transnitration technique. Analysis time was approximately 1.5 min per sample and could detect NO₃’ concentration as low as 0.1 ug NO₃’‐N ml/¹ in plant extracts (10 ug NO₃’‐N g‘¹of plant material).     

Wild edible plants traditionally gathered in Gorbeialdea (Biscay, Basque Country)

This ethnobotanical study aims to describe the domain of wild edible plants in Gorbeialdea (Biscay, Iberian Peninsula), and to assess the cultural importance of the different species and food categories. Field work was conducted between 2008 and 2010, interviewing 103 informants about the traditional use of wild plants for food. The edible use of 49 species was recorded, 45% of them gathered for their fruits. The most important species coincide with those registered in other regions in the north of the Iberian Peninsula (Prunus spinosa, Rubus ulmifolius, Castanea sativa, Fragaria vesca, Rumex acetosa, Vaccinium myrtillus and Arbutus unedo). However, the importance of some species and uses that had not been previously recorded as edible in the ethnobotanical literature of the Iberian Peninsula, highlights the singularity of the area. The consumption of the leaves of Fagus sylvatica, the seeds of Pinus radiata, and the shoots of Pteridium aquilinum are some examples of specific uses. The eating of the fruits of Quercus robur, and Q. ilex was common until some decades ago and is still remembered by the informants. However, the consumption of those fruits has now a social stigma, and as shown in this paper, it can be overlooked by a methodology only based on open interviews. The most important use-category was ‘fruits’, following the trend found in other northern regions of the Iberian and Italian Peninsulas. ‘Snack vegetables’ is also a relevant category, including 35% of the cited species, with a high diversity of chewed plants, mainly as hunger or thirst quenchers. On the contrary, there was a low valorization of condiments and elaborated vegetables.     

Species delimitation,genetic diversity and structure of the European indigenous wild pear (<Emphasis Type="Italic">Pyrus pyraster</Emphasis>) in Saxony,Germany

The present study investigated genetic diversity, structure and hybridization in a collection of the endangered wild pear species Pyrus pyraster (L.) Burgd. A total of 278 putative ‘true type’ P. pyraster trees originating from seven populations in the federal state of Saxony in Germany were analyzed along with 35 pear cultivars commonly cultivated in Saxony. The genetic analysis was performed using nine nuclear microsatellite markers (ncSSR) and two paternally inherited chloroplast marker (cpDNA) amplifying in the intergenic spacer region trnQ–rps16 and the intron region rps16. On basis of the ncSSR dataset after STRUCTURE analysis 80 % of the wild pear individuals were assigned as ‘true type’ P. pyraster genotypes. The cpDNA analysis showed shared haplotypes in P. pyraster and P. communis but with an unequal frequency in both species. The analysis of molecular variance resulted in a moderate (ncSSR) and great (cpDNA) variation among ‘true type’ P. pyraster and the pear cultivars. The genetic diversity in the ‘true type’ P. pyraster populations was still high and the genetic structure between the populations low (ncSSR and cpDNA) indicating a genetic exchange between the populations by pollen and seeds. The clear discrimination between the P. pyraster and P. communis confirms our expectation of the existence of ‘true type’ P. pyraster individuals in the study area. The existing genetic integrity and the high genetic diversity argue for the implementation of preservation measures in P. pyraster.     

EXOGENOUS APPLICATION OF POTASSIUM NITRATE TO ALLEVIATE SALT STRESS IN RICE SEEDLINGS

□ Overall growth characteristics of many plant species cultivated in soil affected by salinity could be alleviated by the application of potassium nitrate (KNO₃) to the soil. The aim of this research was to investigate salt-tolerance in a salt-sensitive rice cultivar, ‘Pathumthani 1’ (PT1), in response to the exogenous application of 11.8 mM KNO₃, in comparison to ‘Homjan’ (HJ), a salt tolerant cultivar. Water potential (ψ_w) in both the roots and leaves of PT1 seedlings under salt stress dropped significantly, while it was maintained in PT1 pretreated with KNO₃, and similarly in HJ. The reduction of leaf water potential was positively related to total chlorophyll degradation, leading to diminished chlorophyll fluorescence, directly affecting growth in plants exposed to salt stress. In salt-sensitive PT1, the application of 11.8 mM KNO₃ improved salt-tolerance via the conservation of water use efficiency, the maintenance of photosynthetic pigments, enhancement of chlorophyll a fluorescence, and stimulation of growth characters.     

Crop–weed hybrids are more frequent for the grain amaranth ‘Plainsman’ than for ‘D136-1’

White-seeded cultivated amaranth [Amaranthus caudatus L., A. cruentus L., and A. hypochondriacus L.] grain is less valuable if contaminated with brown off-type seeds from the hybrid weedy progeny of spontaneous crop–weed crossing. Crop–weed crossing frequency was estimated by using two grain amaranth cultivars. Both cultivars were planted at the same nine locations in the Midwest United States and exposed to pollen from local weedy Amaranthus species. Harvested seeds were grown in a greenhouse, and the frequency of crop–weed hybrids was determined by observing dominant weed traits in the progeny. The cultivar ‘Plainsman’ was approximately tenfold more likely to hybridize with weedy amaranths than was ‘D136-1’. These are the first amaranth cultivars to be evaluated in this way. The reduced hybridization potential of ‘D136-1’ or similar material can be exploited to reduce the occurrence of off-type seed contamination in grain amaranths.     

Influence of nitrogen and potassium on micronutrient content of fifteen cultivars of bermudagrass

Abstract

There is limited information concerning the micronutrient composition of different turfgrass species and cultivars. Bermudagrass [Cynodon dactylon (L.) Pers.] is an important turfgrass utilized throughout the Southeastern and Southwestern states and the transition zone of the United States. A study was conducted to determine the effects of different rates of nitrogen (N) and potassium (K) on the micronutrient content of fifteen bermudagrass cultivars. The cultivars utilized were: ‘Ormond’, ‘Texturf 10’, ‘Tiflawn’, ‘Tufcote’, and ‘U‐3’ [Cynodon dactylon (L.) Pers.]; ‘Everglades’, ‘Midiron’, ‘Midway’, ‘Pee Dee’, ‘Santa Ana’, ‘Tifdwarf, ‘Tifgreen’, ‘Tifway’, and ‘Tifway II’ [Cynodon dactylon (L.) Pers. x Cynodon transvaalensis Burtt‐Davey]; and ‘Sunturf [Cynodon magennisii Hurcombe]. The study was a 2x2 factorial with the factors being two levels each of N and K imposed on the fifteen cultivars. It was a completely randomized design with three replications. The N and K rates were 227 g N and 227 g K 93 m^‐2 month^‐1 (low rates) and 454 g N and 454 g K 93 m^‐2 month^‐1 (high rates) that resulted in four N:K treatment combinations as follows: 1) high N:high K; 2) high N:low K; 3) low N:high K; and 4) low N:low K. Plant tissue samples were collected in late August and analyzed for boron (B), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn). There were differences for the Cu, Fe, Mn, and Zn concentrations for several cultivare under certain treatment combinations. Zinc concentrations exceeded the sufficiency range in all but one instance, while there were several cases in which Fe and Mn concentrations were above the sufficiency range. The levels of B and Cu were within the sufficiency range and there were no differences for B.     

Single species island biogeography and Montana mule deer

The theory of island biogeography supplemented with dynamic concepts from other areas of biology can be applied to a single species. Data series from mule deer Odocoileus hemonius hemonius populations inhabiting diverse mountain as well as prairie habitats were compared. The fawn-doe ratios obtained at 6 months of age were inversely correlated (r = ?0·97; p < 0·01) with ‘island’ size as indicated by the percentage of cover. Populations inhabiting small islands of cover in the prairie consistently had higher winter fawn-doe ratios than those of the relatively secure mountain habitats. Cover fragmentation and low security level of the prairi populations relates to a high annual turnover rate compared with that of the mountain populations. The impact of cover fragmentation is consistent with this interpretation of theory which pictures reproduction as annual recolonisation. This approach may be useful in predicting hunting and ecological impact effects.     

Occurrence of foraminifera,molluscs and ostracods adjacent to the industrialized shoreline of Canso Strait,Nova Scotia

The distribution of foraminifers, molluscs and ostracods was investigated in a moderately polluted part of the Canso Strait. These three groups of invertebrates show a relatively high, moderate and low tolerance to industrial effluents respectively. Maps of species distributions and of trace metal concentrations indicate that the usual direction of movement of contaminated surface waters is southward. In the marine environment adjacent to the industrialized shoreline the productivity of the Foraminifera is relatively low compared to values observed in the less polluted areas of the Strait. The relatively large numbers of Eggerella advena reflect its ability to compete successfully and to reproduce in modified or ‘artificial’ environments. Stressed environments near pollution sources in the Strait are characterized by large numbers of E. advena, Elphidium incertum/clavatum group, the mollusc species Modiolus modiolus, and several ostracods including Baffinicythere emarginata and Muellerina canadensis.     

A novel method to evaluate the phytotoxic potential of low ozone concentrations using poplar cuttings

Six-week-old rooted cuttings of Populus nigra L. ‘LOENEN’ and Populus maximowiczii Henri X Populus nigra L. ‘ROCHESTER’, differing in their phenomenological sensitivity to O₃, were submitted to low concentrations of O₃, NO_x, and SO₂. Exposure was performed in open top-chambers from 25.5. until 6.7.1988. Comparing the response of the two poplars by 77 biochemical criteria the macroscopic O₃- sensitivity of ‘LOENEN’ was clearly reflected in changes of the pool sizes of the different nonstructural carbohydrates, polyols, and phenolics of the leaf-lamina, petiole, shoot-axis, and roots. In contrast, both varieties revealed the same response to NO_x/SO₂-mixtures. It can be concluded that ‘LOENEN’ together with ‘ROCHESTER’-poplars as controls, are an appropriate system to specifically indicate O₃ in a mixture of air pollutants.     

‘Decomposer’ Basidiomycota in Arctic and Antarctic ecosystems

Current knowledge concerning ‘decomposer’ Basidiomycota in Arctic and Antarctic ecosystems is based on two sources: (a) collections and surveys of basidiomata, which have resulted in high-quality catalogues of species, although much of the species’ distribution and ecology are tentative and (b) isolations from soils and plant litter which typically result in a “low incidence of basidiomycetes” [Dowding, P., Widden, P., 1974. Some relations between fungi and their environment in tundra regions. In: Holding, A.J., Heal, O.W., MacLean Jr., S.F., Flanagan, P.W. (Eds.), Soil Organisms and Decomposition in Tundra. Tundra Biome Steering Committee, Stockholm, Sweden, pp. 123–150], probably because of selectivity in isolation methods. In the few molecular studies carried out in Arctic and Antarctic soils to date, basidiomycetes, particularly yeasts, have been found. These techniques should give better estimates of the order of magnitude of fungal species richness in Arctic and Antarctic soils, although caution should be used concerning primer choice and amplification conditions. From collections in Arctic regions, species of basidiomycetes appear to be circumpolar in distribution with restricted endemism. Using culture-independent methods, it should be possible to test whether selected Arctic or Antarctic species are truly cosmopolitan, circumpolar, endemic, or are cryptic phylogenetic species.Particularly in Arctic ecosystems, potential ‘decomposer’ fungi in soils and roots may be from phylogenetically diverse taxa, and currently it is unclear whether ‘decomposer’ basidiomycetes are the fungi undertaking the majority of organic matter decomposition in Arctic and Antarctic ecosystems. For example, in some recent studies, wood decomposition in cold Arctic and Antarctic sites appears to proceed via ‘soft rot’ by anamorphic ascomycetes (e.g. Cadophora species), rather than by ‘white rot’ or ‘brown rot’ basidiomycete species. Additionally, it appears basidiomycetes and ascomycetes as ericoid and ectomycorrhizal fungi have the potential to be involved directly in decomposition.Given that profound changes are likely to occur in patterns of vegetation (Arctic and Antarctic) and size of soil carbon (C) pools (particularly in the Arctic) by the end of this century, it is necessary to know more about which species of ‘decomposer’ basidiomycetes are present and to try to define their potentially pivotal roles in ecosystem C (and N) cycling. One solution to characterise further the identity and roles of these fungi in a logical way, is to standardise methods of detection and ‘function’ at networks of sites, including along latitudinal gradients. Results of functional tests should be related to community structure, at least for ‘key’ species.     

Genetic diversity in cultivated yam bean (<Emphasis Type="Italic">Pachyrhizus</Emphasis> spp.) evaluated through multivariate analysis of morphological and agronomic traits

Yam bean [Pachyrhizus DC.] is a legume genus of the subtribe Glycininae with three root crop species [P. erosus (L.) Urban, P. tuberosus (Lam.) Spreng., and P. ahipa (Wedd.) Parodi]. Two of the four cultivar groups found in P. tuberosus were studied: the roots of ‘Ashipa’ cultivars with low root dry matter (DM) content similar to P. erosus and P. ahipa are traditionally consumed raw as fruits, whereas ‘Chuin’ cultivars with high root DM content are cooked and consumed like manioc roots. Interspecific hybrids between yam bean species are generally completely fertile. This study examines the genetic diversity of the three crop species, their potentials for breeding and the identification of useful traits to differentiate among yam bean genotypes and accessions. In total, 34 entries (genotypes and accessions) were grown during 2000?2001 at two locations in Benin, West Africa, and 75 morphological and agronomical traits, encompassing 50 quantitative and 25 qualitative characters were measured. Diversity between entries was analyzed using principal component analysis, cluster analysis, multivariate analysis of variance and discriminant function analysis. Furthermore, phenotypic variation within and among species was investigated. Intra- and interspecific phenotypic diversity was quantified using the Shannon–Weaver diversity index. A character discard was tested by variance component estimations and multiple regression analysis. Quantitative trait variation ranged from 0.81 (for total harvest index) to 49.35% (for no. of storage roots per plant). Interspecific phenotypic variation was higher than intraspecific for quantitative traits in contrast to qualitative characters. Phenotypic variation was higher in overall for quantitative than qualitative traits. In general, intraspecific phenotypic variation ranged from 0.00 to 82.61%, and from 0.00 to 80.03% for quantitative and qualitative traits, respectively. Interspecific phenotypic variation ranged from 0.00 to 95.02%, and 0.00?81.58% for the two trait types, respectively. The Shannon–Weaver diversity index (H′) was in general high and over 0.80 for most of the trait. Diversity within P. tuberosus was higher than within P. erosus and P. ahipa. Across the 50 quantitative and 25 qualitative traits, the Shannon–Weaver diversity index of intra- and interspecific variation was around 0.83 and 0.51, respectively and was lower for qualitative than for quantitative traits. Monomorphism was observed in eight qualitative traits and one quantitative character. The first, second and third principal components explained, respectively, 39.1, 21.3 and 8.3% of the total variation in all traits. Pachyrhizus erosus, P. ahipa, and P. tuberosus (‘Chuin’ and ‘Ashipa’) were clearly separated from each other by these analyses. Multivariate analysis of variance indicates significant differences between Pachyrhizus species for all individual or grouped traits. Discriminant function analysis revealed that the first two discriminant functions were almost significant. Biases due to unbalanced sample size used per species were small. Within each species a similar amount of diversity was observed and was determinable to 70% by only ten traits. We conclude that the cultivated yam bean species represent distinct genepools and each exhibits similarly large amounts of genetic diversity.     

Study of Soil Fertility and Plant Nutrition of Proteas Cultivated under Subtropical Conditions

Abstract: A study of soil physicochemical characteristics and mineral nutrition of four cultivars of Leucospermum cordifolium (‘Scarlett Ribbon,’ ‘High Gold,’ ‘Veldifre,’ ‘Sunrise’) and Leucospermum patersonii species was carried out along 2 years in commercial protea plantations, distributed throughout a subtropical region (La Palma Island, Canarian Archipelago). Soils presented a slightly acid pH range, whereas organic matter showed suitable values. Generally, available soil phosphorus (P) contents were less than 25 mg kg^?1, with high available potassium (K) and calcium (Ca) levels, though the ratio of Ca of the sum of available cations was usually appropriate. Despite the high electrical conductivity (EC) levels (4.31–8.87 dS m^?1) determined in some soils, no salinity symptoms were ever detected. Distribution and behavior of foliar nutrients nitrogen (N), P, K, Ca, magnesium (Mg), and sodium (Na) along time showed that nutritional needs varied in some cases among cultivars and species. L. patersonii presented the least N concentration, whereas ‘High Gold’ and ‘Veldfire’ had the greatest levels. Data denoted that P requirements were larger in younger plants, during the recovery after pruning, and while new buds developed. ‘Sunrise’ cultivar stood out for its large foliar levels of P, whereas ‘Scarlett Ribbon’ and ‘Veldfire’ had the least K contents. As a general pattern, K decreased in winter samplings. L. patersonii species and the cultivar ‘Sunrise’ exhibited the highest Ca values, and the same was true for Mg only in the species. A special need for Na appeared in all the cultivars and species studied. L. patersonii and the cultivar ‘Sunrise’ showed the greatest Na levels. A general stabilization of nutrient concentrations was observed in the fourth, fifth, and/or sixth samplings, so that November is recommended for taking samples for current foliar analysis. In this context, foliar ranges for the studied nutrients are suggested.     

The impoverishment of the bryophyte and lichen flora of the Dutch chalk grasslands in the thirty years 1953–1983

The Dutch chalk grasslands were formerly very rich in bryophyte and lichen species. A comparison of data from Barkman (1953) and more recent inventories yielded the following results: (a) Lichens have disappeared nearly completely from the Dutch chalk grasslands; (b) Many characteristic acrocarps (e.g., Tortella spp., Trichostomum spp., Aloina spp., Pleurochaete squarrosa) and some pleurocarps (Abietinella abietina, Camptothecium lutescens) have decreased drastically; (c) Some common litter-indicator species (Brachythecium rutabulum and others) are now increasing.We hypothesise that this change is mainly a result of combined effects of the abandonment of the old grazing regime, which is in only a few places replaced by mowing, and of air pollution. We are strongly in favour of current attempts to reintroduce grazing by the old race of ‘Mergelland’ sheep.