Transgenic approaches for genetic improvement in groundnut (Arachis hypogaea L.) against major biotic and abiotic stress factors

Cultivated groundnut (Arachis hypogaea L.) is considered as one of the primary oilseed crops and a major fodder for cattle industry in most of the developing countries, owing to its rich source of protein. It is due to its geocarpic nature of growth that the overall yield performance of groundnut is hindered by several biotic and abiotic stress factors. Multidimensional attempts were undertaken to combat these factors by developing superior groundnut varieties, modified with integral mechanism of tolerance/resistance; however this approach proved to be futile, owing to inferior pod and kernel quality. As a superior alternative, biotechnological intervention like transformation of foreign genes, either directly (biolistic) or via Agrobacterium, significantly aided in the development of advanced groundnut genotypes equipped with integral resistance against stresses and enhanced yield attributing traits. Several genes triggered by biotic and abiotic stresses, were detected and some of them were cloned and transformed as major parts of transgenic programmes. Application of modern molecular biological techniques, in designing biotic and abiotic stress tolerant/resistant groundnut varieties that exhibited mechanisms of resistance, relied on the expression of specific genes associated to particular stress. The genetically transformed stress tolerant groundnut varieties possess the potential to be employed as donor parents in traditional breeding programmes for developing varieties that are resilient to fungal, bacterial, and viral diseases, as well as to draught and salinity. The present review emphasizes on the retrospect and prospect of genetic transformation tools, implemented for the enhancement of groundnut varieties against key biotic and abiotic stress factors.     

Combined effect of salinity and temperature on Spirorbis spirorbis L. and Circeus spirillum L. larvae from the White Sea

The combined effect of salinity and temperature on Spirorbis spirorbis L. and Circeus spirillum L. larvae from the White Sea was studied in the laboratory experiments. In the White Sea, S. spirorbis is distributed through the depth of 1-20 m and is affected by all varieties of fluctuations in salinity and temperature. C. spirillum lives in more wide range of depths 1-55 m and is more stenohaline. S. spirorbis larvae are sufficiently more resistant to the low salinity (10‰) than C. spirillum larvae. Both species are stenothermic. Highest survivorship of S. spirorbis larvae was marked under 5 °C in all experimental salinities. Under temperature treatments of 10-15 °C, the larval survivorship was sufficiently restricted in all salinities. Highest survivorship of C. spirillum larvae was also marked under 5 °C but in more narrow salinity range.The number of larvae undergoing metamorphosis in both species was very low, only about 10% of the total number. Highest number of successful attachments in both species was marked in high salinities (25-30‰) and does not exceed 25% of survivors. Experimental data suggests that salinity and temperature affect directly general survivorship of the larvae and secondary-attachment and metamorphosis processes.     

Influence of starvation on larval development of Carcinus maenas L. (Decapoda : Portunidae)

Lethal and sublethal effects of particular starvation events were investigated in larvae of Carcinusmaenas L. Mean survival times of continuously starved zoeae-1 were approximately twice the normal stage duration (12, 18, 25°C), and both increased with falling temperatures. At 6°C zoea-1 was unable to develop to stage-2. No larva retained the ability for successful further development if starved for half the stage duration time and was then refed. The zoea-1 larvae had to feed for at least 20 % of the normal stage duration for some larvae to moult to zoea-2. Some initial feeding was necessary to start zoea-1 development. Beyond a certain point of energy and accumulation of reserves development of the larvae seems to continue regardless of feeding rates. The demands for larval feeding correspond very well with the larval moulting cycle. Larvae of C. maenas proved to be well adapted to natural shortage of food.     

Diversity,composition, and structure of tropical dry forests in Central America

Tropical dry forests have been reduced to less than 0.1% of their original expanse on the Pacific side of Central America and are considered by some to be the most endangered ecosystem in the lowland tropics. Plots 1000 m² were established in seven tropical dry forests in Costa Rica and Nicaragua in order to compare levels of species richness to other Neotropical dry forest sites and to identify environmental variables associated with species richness and abundance. A total of 204 species and 1484 individuals 2.5 cm were encountered. Santa Rosa National Park was the richest site with the highest family (33), genera (69), and species (75) diversity of all sites. Species richness and forest structure were significantly different between sites. Fabaceae was the dominant tree and shrub family at most sites, but no species was repeatably dominant based on number of stems in all fragments of tropical dry forest. Central American dry forests had similar species richness when compared to other Neotropical forests. There was no correlation between forest cover within reserves, or precipitation and plant species richness. There was a significant correlation between anthropogenic disturbance (intensity and frequency of fire, wood collection, grazing) and total species richness, tree and shrub species richness, and liana abundance. These results suggest controlling levels on anthropogenic disturbance within reserves should be a high priority for resource managers in Central America. Further research in forest fragments which examine individual and a combination of disturbance agents would help clarify the importance of anthropogenic disturbance on species richness and abundance.     

Latitudinal differences in fish community trophic structure,and the role of fish herbivory in a Costa Rican stream

Synopsis We experimentally manipulated fish grazing pressure to determine whether fish herbivory played an important role in the structure of a Costa Rican stream. Non-planktonic plant matter represented a significant percentage ( 25%) of the diet of 77% of the 17 fish species in the community. We prevented fish grazing on macrophytes, tree leaves, and periphyton using fish exclusion cages. Fish grazedPanicum sp., used as a generalized aquatic macrophyte, to the stems after 6 days in control areas, and consumed all or much ofFicus insipida andMonstera sp. leaves when placed in the stream after 48 hours. Plants and leaves experimentally protected by cages remained intact. In periphyton studies, fifty percent more ash free dry weight occurred on 25 × 25 cm floor tiles protected from fish grazing by cages than on tiles in roofless controls exposed to fish grazing for 19 days, suggesting a reduction in periphyton biomass. These results demonstrate that fish herbivory affects macrophyte abundance, and impacts the amount of leaf litter in the stream. Fish herbivory may also have an important effect on overall periphyton biomass. Herbivorous fish species generally represent a larger proportion of the total fish community in tropical compared to temperate streams; thus fish grazing is more likely to have an important influence on plant and animal abundances and distributions in tropical streams.     

Nutrient cycling in a tropical seasonal rain forest of Xishuangbanna, Southwest China. Part 1: tree species: nutrient distribution and uptake

Tropical rain forests are characterized by large numbers of the species with diverse growth habits. The objective of the present study was to determine the distribution of nutrient content in the major trees of the tropical rain forests in Xishuangbanna. This will improve the understanding of the nutrient losses from such sites that result from harvesting and flow of nutrients within the ecosystem and lead to the development of effective and rational forest management strategies. Based on the results in this study, the distribution of nutrients among biomass components of trees varied: The ordering of major elements concentrations was K>N>Mg>Ca>P in branch, stem and root tissues but was N>K>Mg>Ca>P in leaves. The maximum amount of all nutrients per ha occurred in the stems followed by branches, roots and leaves. Of the total uptake of 6167.7 kg ha⁻¹ of all nutrients, the contribution of various nutrients was found to be N (2010.6 t ha⁻¹), P (196.3 t ha⁻¹), K (2123.8 kg ha⁻¹), Ca (832 kg ha⁻¹) and Mg (1005 kg ha⁻¹). However, comparing the nutrient uptake of other tropical and sub tropical forests, the results indicated that rates for the Xishuangbanna forests were 20–35% lower than previously reported values.     

Comparison of low salinity tolerance in Callinectes sapidus Rathbun and Callinectes similis Williams postlarvae upon entry into an estuary

Planktonic larvae of estuarine crabs are commonly exported to the continental shelf for development and then return to coastal and estuarine areas as postlarvae (megalopae). Megalopae returning to estuaries must be adapted to survive in brackish water whereas those of coastally distributed species should not need such adaptations. We investigated 1) whether megalopae of the estuarine crab Callinectes sapidus and the coastal crab Callinectes similis undergo changes in salinity tolerance upon entry into an estuary and 2) what factors induce those changes. Megalopae were collected at a coastal site and a nearby estuarine site and exposed to a range of salinities (5, 10, 15, 20 and 30) for 6 h. Percent survival was determined after 24 h reintroduction to the collection site water. We also investigated 1) whether increased salinity tolerance was induced by reduced salinity or estuarine chemical cues, 2) the time to acclimation and 3) the salinity necessary for acclimation. C. sapidus megalopae from the estuarine site were more likely to survive exposure to low salinities than those from the coastal site. C. sapidus megalopae from the coastal site exhibited increased survival after acclimation to salinities of 27 and 23 for 12 h. Estuarine chemical cues had no effect on salinity tolerance. C. similis megalopae were less likely to survive at low salinities and did not exhibit an acclimation response upon exposure to reduced salinities. These results suggest that megalopae of C. sapidus are physiologically adapted to recruit to estuaries whereas megalopae of C. similis are unable to acclimate to low salinity conditions.     

Mapping species density of trees,shrubs and vines in a tropical forest,using field measurements,satellite multiespectral imagery and spatial interpolation

We estimated the number of species in a tropical forest landscape in Quintana Roo, Mexico, based on the relationship between reflectance values of satellite imagery and field measurements of plant species density (mean number of species per plot). Total species density as well as that of tree, shrub and vine species were identified from 141 sampling quadrats (16543 individuals sampled). Spatial prediction of plant diversity was performed using universal kriging. This approach considered the linear relationship between plant species density and reflectance values of Thematic Mapper™, as well as the spatial dependence of the observations. We explored the linear relationships between spectral properties of TM bands and the species density of trees, shrubs and vines, using regression analysis. We employed Akaike Information Criterion (AIC) to select a set of candidate models. Based on Akaike weights, we calculated model-averaged parameters. Linear regression between number of species and reflectance values of TM bands yielded regression residuals. We used variogram analysis to analyze the spatial structure of these residuals. Results show that accounting for spatial autocorrelation in the residual variation improved model R² from 0.57 to 0.66 for number of all species, from 0.58 to 0.65 for number of tree species, from 0.26 to 0.41 for number of shrub species and from 0.13 to 0.17 for species density of vines. The empirical models we developed can be used to predict landscape-level species density in the Yucatan Peninsula, helping to guide and evaluate management and conservation strategies.     

Distribution, settlement, and growth of first-year individuals of the shipworm Teredo navalis L. (Bivalvia: Teredinidae) in the Port of Rotterdam area, the Netherlands

During the period 2004-2008 the distribution, settlement, and growth of first-year shipworms (Teredo navalis L., 1758) was studied by exposing fir and oak panels in the Port of Rotterdam area, which is situated in the Rhine-Meuse estuary in the Netherlands and covers the complete salinity gradient. Shipworms were found yearly in the western large polyhaline harbours. On only a few occasions were they were found in harbours that showed large seasonal and daily fluctuations in salinity. In 2006 the shipworm was found in fir panels 20 km upstream from the polyhaline harbours, demonstrating their ability to travel with the tidal currents over considerable distances and to settle once the abiotic conditions become favourable. Although the water temperatures allowed them to breed from April until November, infestations were not found before September, and from the size of the animals in the panels it was concluded that in the Port of Rotterdam area they spawned from August until the end of November. The settlement height was negatively correlated with the distance of the panels to the sea floor. In the first season after settlement they showed a substantial growth rate of 0.18 cm day⁻¹. The longest shipworm found measured 36.8 cm after 4-5 months of growth after settlement. Infestations and growth were lower in oak than in fir wood. In 2006 the maximum consumption of wood by individuals settled in the same year in panels at the bottom accounted for 12.4%. Shell size and body length of the animal after the first season of growth showed a significant positive logarithmic relation. In both 2006 and 2007 a similar relation between the average boring tube diameter and the length of the animals was found. Lower river discharges leading to salinisation of the eastern part of the Port of Rotterdam area create conditions favourable for the shipworm, with serious consequences for the piles upon which the quays are built.     

Spatial distribution and secondary production of Copepoda in a tropical reservoir: Barra Bonita, SP, Brazil.

The present paper aims to describe the spatial distribution of zooplankton copepods, their biomass and instantaneous secondary production, in Barra Bonita, a large eutrophic, polymitic reservoir (22 degrees 29' S and 48 degrees 34' W) on the Tietê River, of the Paraná basin. Sampling was carried out during two seasons: dry winter and rainy summer. Species composition, age structure and numerical density of each copepod species population were analyzed at 25 sampling stations. Secondary production was calculated for Copepoda, the dominant group in zooplankton communities, taking Calanoida and Cyclopoida separately. Copepoda represented the largest portion of the total zooplankton biomass, the dominant species being Notodiaptomus iheringi among the Calanoida and Mesocyclops ogunnus and Thermocyclops decipiens among the Cyclopoida. The production of Copepoda was higher during the rainy summer (23.61 mgDW.m(-3).d(-1) in January 1995) than during the dry winter season (14 mgDW.m(-3).d(-1) in August 1995), following the general pattern of abundance for the whole zooplankton community. Among the copepods, Cyclopoida production was higher than that of Calanoida, a pattern commonly observed for tropical lakes and reservoirs. Barra Bonita copepods are very productive, but there was a great degree of spatial heterogeneity, related to the physical and chemical conditions, particularly the level of nutrients and also to phytoplankton biomass.     

Changes in behaviour and eye-morphology of BoreomysisMegalops G.O. Sars (Crustacea : Mysidacea) following exposure to short periods of artificial and natural daylight

Boreomysis megalops G.O. Sars were collected from 240 m depth using a protective cod-end, which shielded the eyes from light exposure. Animals were divided into groups which were exposed to darkness (DE) or to natural or artificial daylight (LE) for periods of 1–15 min or 4 h. Some animals were thereafter kept in aquaria under simulated habitat light conditions (light/dark cycles). The animals were observed in infra-red (IR) light. DE animals showed a vertical zonation behaviour in the laboratory similar to that obtained from sledge data: i.e. the animals stayed close to the bottom during daytime (light) and spread out vertically at night (darkness).LE individuals showed putative pathological changes both in zonation behaviour in the laboratory and in eye-morphology. The photoreceptor membranes of the six main retinula cells were damaged. The seventh cell was unaffected by light exposures. A correlation was found between the extent of damage to the eye and the degree of modification of vertical zonation behaviour. The groups exposed to the least light showed the smallest changes in zonation behaviour and eye-morphology. The light induced changes were not reversed even after 4 days in the aquarium under simulated habitat light conditions. In conclusion, deep living animals with well-developed and very light sensitive eyes should be protected from daylight during sampling and handling. IR light should be used for observation purposes.     

Biomarker responses of the estuarine brown shrimp Crangon crangon L. to non-toxic stressors: Temperature, salinity and handling stress effects

Biochemical biomarkers in common estuarine species, such as the brown shrimp Crangon crangon, have the potential to provide early warning of contaminant exposure from field collected samples and through the development of in situ tests. The biomarkers acetylcholinesterase (AChE), lactate dehydrogenase (LDH) and glutathione S-transferase (GST) have been shown to provide evidence of exposure to contaminants in a number of species and field situations. As they may naturally respond to the marked physicochemical changes found in estuaries (thus confounding contaminant-induced effects), this work aims to determine the effects of salinity, temperature and handling stressors on these biomarkers in C. crangon.AChE recovery in field-collected shrimp transplanted to clean laboratory conditions suggests the presence of inhibiting factors at the sampling site (River Minho estuary). Maintenance time in stock tanks had effects that led to the choice of a minimum 15-day maintenance period of C. crangon in the laboratory before subsequent use of the enzymes as effect criterions in toxicity assays. Field levels of biomarker activity were unaffected following field-laboratory transportation of C. crangon, making this factor unlikely to jeopardize detection of contaminant associated effects. LDH levels were significantly lower under conditions that mimic a diurnal salinity fluctuation, increasing under low salinity conditions; this potentially indicates increased energy costs associated with raised osmoregulatory demands. It is recommended that a lower limit to field exposure of in situ tests should be based on salinity. Higher temperatures led to higher AChE activities and this is in agreement with the existing evidence of increases of endogenous AChE levels as a function of temperature (within a certain range). To avoid misinterpretation of biomarker responses, studies such as this are an important contribution to the establishment of reference activity levels against which biomarker changes can be estimated and are therefore essential preliminary steps in the development of in situ bioassays using biomarkers.     

Responses of a fringing Cyperus papyrus L. swamp to changes in water level

Over a 9-year period (1993–2001), the land-water width of a papyrus fringe on the southern shore of Lake Naivasha, Kenya, varied between 40 and 60 m. Increases in width via rhizome spreading into open water followed the 1997/1998 El Niño flood when water depths rose by about 2 m. Germination of papyrus seeds also responded to water depth with a mean ± S.E. rate in experiments of 23 ± 6% after 21 days when water level was 5 cm below the sediment surface. No germination occurred when sediment was flooded or allowed to desiccate. Rhizome spreading from floating mats appeared to be favoured by deep water with seedling spread favoured on newly inundated, low-gradient slopes in shallow water. Although natural regenerative capacity was influenced by water depth, the height, density, biomass and chemical content of papyrus were not. Total average biomass along a land-water transect was 6950 ± 860 g m⁻² which was large in relation to nutrient and mineral contents. Culms contained 0.47 ± 0.14% N and 0.06 ± 0.05% P and rhizomes 0.71 ± 0.21% and 0.10 ± 0.06%. Sediment underlying the swamp was aerobic and there were small land-water gradients in the BOD of swamp water and sediment. However, chemical gradients were weak compared with wider papyrus swamps elsewhere. Lake and swamp water mixed in the narrow fringe studied and residence times for organic matter may not have been long enough for organic material to mineralise before entering lake water.     

Spatial distribution of primates in a mosaic of colonizing and old growth forest at Ngogo, Kibale National Park, Uganda

Primate censuses were conducted in a mosaic of colonizing (two locations) and old-growth forests using line transect methods at the Ngogo study site, Kibale National Park, Uganda. Black and white colobus monkeys (Colobus guereza) were encountered more frequently in the colonizing forests than in the old growth forest, while chimpanzees (Pan troglodytes) were encountered more frequently in the old growth forest than in colonizing forests. Although not significant, results suggest that blue monkeys (Cercopithecus mitis) frequented colonizing forests more often than old growth forest. The encounter rates of mangabey (Lophocebus albigena), and redtail (Cercopithecus ascanius) groups were ambiguous with their density being higher in some colonizing forests but not others as compared to old-growth forest. No significant differences were detected for baboons (Papio anubis), Lhoests (Cercopithecus lhoesti), and red colobus monkeys (Piliocolobus tephroscales). The conversion of forests to farmland is one of the major problems encountered in primate conservation. This study shows that secondary forests replacing anthropogenic grasslands have the potential of supporting some primate species such as black and white colobus, redtail monkeys, and possibly blue monkeys. Therefore, such areas should not be given up but should be conserved for the benefit of primates that can survive in secondary forests; as the forests mature further, primate species that are adapted to old growth forest will colonize the area provided there is a nearby source.     

Sex expression and reproductive biology in a tree species, Fraxinus excelsior L

We investigated Fraxinus excelsior breeding system using field data collected in a natural population and in a seed orchard. First, we attested functional trioecy (co-occurrence of males, hermaphrodites and females), with males producing pollen, hermaphrodites producing both pollen and seeds simultaneously, and females producing seeds. Second, we found that the reproductive system of F. excelsior was not labile, as sex expression seemed to be stable through time. Third, gender is genetically determined since different trees belonging to the same clone in the orchard exhibit similar sexual phenotypes.     

Spatial structure of fish assemblages in a tropical estuarine lagoon: combining multivariate and geostatistical techniques

The spatial structure and seasonal changes of estuarine fish assemblages in the Ciénaga Grande de Santa Marta (CGSM) were analysed based on four seasonal comprehensive surveys conducted in 1993-1994 and 1997. Geostatistical and multivariate techniques were used to: (a) determine seasonal changes in spatial distribution of the species richness, and (b) identify assemblages of estuarine fish and their relation to abiotic factors. Potential biotic interactions affecting the assemblage structure were also explored. A total of 11075 individuals representing 39 species were collected, with Eugerres plumieri, Diapterus rhombeus, Micropogonias furnieri, Mugil incilis, Cathorops spixii, Elops saurus and Anchovia clupeoides as dominant species between seasons. Spatial distribution of fish richness differed between rainy and dry seasons in each year, whereas species mapping showed spatial patchiness in 1993-1994 and gradients during 1997. Strong evidence of species saturation was found in all seasons, suggesting biotic interactions limiting species richness at a threshold density of ca. 50 ind./5000 m². Marine, marine-estuarine and freshwater species were classified in each season according to their capability to cope with salinity fluctuations. Associations defined by functional feeding guilds were also identified. Empirical and statistic evidence showed that fish assemblages differed between seasons within each year, and each assemblage was always dominated by a small number of species, notably E. plumieri in both years 1993-1994 and 1997. Between-season differences in fish assemblage structure in the CGSM seem to be driven by abiotic factors; however, evidence of species saturation could suggest the existence of density-dependent factors operating together.     

Morphological variation and relationships of Georgian populations of Vitis vinifera L. subsp. sylvestris (C.C. Gmel.) Hegi

Georgia is considered as one of the regions where for the first time wild growing grapevine plants were used and taken into cultivation by men. An ampelographic and ampelometric study of leaf characters and flower landmark morphometrics was carried out in seven populations of wild grapevine located in four river basins of three geographic regions – Western (1 popul.), Eastern (5 popul.) and Southern (1 popul.) Georgia, and then compared using principal component analysis and multivariate discriminant analysis allowing the populations to be distinguished. Lengths of main leaf veins and nectaries in male flowers were the variables, which allowed the best discrimination among populations. A mutation leading to white-fruited grapevine is found in one population. Pubescence varies within populations and even within an individual genome and could be used as a discriminant trait only in combination with shapes and sizes of leaves and other morphological characters. The results revealed significant differences among populations located in different geographic regions of the Southern Caucasus area, but the five investigated populations from Eastern Georgia differ only insignificantly. The high morphological variability of wild grapevine in Georgia might be considered as characterizing the large gene pool that contributed to the domestication process of grapevine.     

Distribution, diversity and environmental adaptation of highland papayas (Vasconcellea spp.) in tropical and subtropical America

Vasconcellea species, often referred to as highland papayas, consist of a group of fruit species that are closely related to the common papaya (Carica papaya). The genus deserves special attention as a number of species show potential as raw material in the tropical fruit industry, fresh or in processed products, or as genetic resources in papaya breeding programs. Some species show a very restricted distribution and are included in the IUCN Red List. This study on Vasconcellea distribution and diversity compiled collection data from five Vasconcellea projects and retrieved data from 62 herbaria, resulting in a total of 1,553 georeferenced collection sites, in 16 countries, including all 21 currently known Vasconcellea species. Spatial analysis of species richness clearly shows that Ecuador, Colombia and Peru are areas of high Vasconcellea diversity. Combination of species occurrence data with climatic data delimitates the potential distribution of each species and allows the modeling of potential richness at continent level. Based on these modeled richness maps, Ecuador appears to be the country with the highest potential Vasconcellea diversity. Despite differences in sampling densities, its neighboring countries, Peru and Colombia, possess high modeled species richness as well. A combination of observed richness maps and modeled potential richness maps makes it possible to identify important collection gaps. A Principal Component Analysis (PCA) of climate data at the collection sites allows us to define climatic preferences and adaptability of the different Vasconcellea species and to compare them with those of the common papaya.