Germplasm Sources for Improvement of Forage Quality in Lotus corniculatus L. and L. uliginosus Schkuhr (Fabaceae)

Extensive germplasm resources are present in collections of Lotus corniculatus and L. uliginosus, two forage species that are valuable in situations where other legumes are not persistent. Naturalised populations in many regions are the primary gene pool for genetic improvement of these species and interspecific hybrids are an important source of variation for agronomic and forage quality traits. Although previous research has provided evidence that selection for optimal levels of condensed tannins and herbage productivity are feasible breeding objectives, less is known about correlations of condensed tannin with other parameters of nutritive value. A germplasm collection of 38 accessions in both species from 9 geographic regions was used as a data base to determine these correlations. Forage of each accession was sampled in two successive years from a field site in south-eastern Australia and analysed for condensed tannin, in vitro digestible dry matter, nitrogen, acid detergent fibre and neutral detergent fibre. In both species condensed tannin was negatively correlated with in vitro digestible dry matter and nitrogen. This result helped to identify potentially valuable accessions with low condensed tannin (<4% of dry weight) and high in vitro digestible dry matter (>70%). One of these was an interspecific hybrid of L. uliginosus and L. corniculatus, confirming the view that interspecific hybridization would be a valuable avenue for improvement of agronomic and forage quality characters in Lotus species.     

Quantitative and Qualitative Traits of Natural Ecotypes of Perennial Grasses (Dactylis glomerata L., Festuca arundinacea Schreb., Phalaris tuberosa L., Brachypodium rupestre (Host) R. et S.) Collected in Southern Italy

In 1999, natural populations of Dactylis glomerata L., Festuca arundinacea Schreb., Phalaris tuberosa L. and the macrotherm species Brachypodium rupestre (Host) R. et S., were collected as seed in Southern Italy (Apulia, Basilicata and Campania regions) to evaluate the potential as forage of native germplasm under dry conditions, using available commercial cultivars as controls. The persistence of accessions, biometric, phenologic, productive and qualitative parameters of forage have been studied for a 3-year period (2000–2002) in a typical Mediterranean environment. D. glomerata is widely present in the studied area with two subspecies (subsp. glomerata L., subsp. hispanica (Roth) Nyman). The research pointed out significant differences in plant size, earliness and single plant dry matter (DM) production. All the natural ecotypes belonging to this species showed higher persistence than the control cultivars. Some natural ecotypes appeared to have potential for improving DM yield (subsp. glomerata ecotypes) and reducing neutral detergent fibre (NDF) content (subsp. hispanica ecotypes). Natural ecotypes belonging to F. arundinacea, P. tuberosa, and B. rupestre are sporadically present in the studied area. Among them, two ecotypes of P. tuberosa, showing higher winter growth and earliness compared to cv. ‘Holdfast’, seem to be interesting for a future breeding programme.     

Coloured potatoes (Solanum Tuberosum L.) – Anthocyanin Content and Tuber Quality

Anthocyanins gain more and more importance as natural colourants. Besides many other plant species, coloured potatoes could serve as a potential source. Therefore, 27 potato cultivars and four breeding clones of different origin were analysed for their anthocyanin contents in fresh weight (fw). On average the highest amounts of anthocyanins were found in the skin (0.65 g kg⁻¹ fw) of potatoes. The corresponding values of samples taken from whole tubers (0.31 kg⁻¹ fw) and flesh (0.22 kg⁻¹ fw) were significantly lower (p<0.03). The analysis revealed considerable differences in the amounts of anthocyanins between the 31 cultivars/breeding clones. Among them ȁ8Peru Purpleȁ9 revealed the highest anthocyanin content in the skin with 2.96 g kg⁻¹ fw. A similar high value was reached by ȁ8Violettfleischigeȁ9 and clone 1.81.202–92 N. Also for the other two types of samples, flesh and whole tubers, these three genotypes exhibited the highest level of anthocyanins. Interestingly, different rates of nitrogen fertilization at 100 and 200 kg ha⁻¹ had no significant effect on the pigment content of potatoes. The same was observed with respect to the year or the location of plant growth. There were also no significant changes in the anthocyanin contents of tubers during storage for 135 days. In dry matter, starch and protein contents the coloured potato cultivars/breeding clones were comparable with traditional cultivars. Further tests have shown that the glycoalkaloids were mainly localized in the skin of coloured potatoes.     

Vigna vexillata (L.) A. Rich. Cultivated as a Root Crop in Bali and Timor

Vigna vexillata is considered as a pantropical distributed wild species closely related to the cowpea (Vigna uniculata) and adapted to infertile soils. The species is occasionally used for its storage roots as well as forage and erosion control plant. The objective of this study was to pursue personal communications that V. vexillata has be transformed into a cultivar in Indonesia. Seven Indonesian islands were visited (Java, Bali, Sumba, Flores, Timor, Kalimantan and Sulawesi). Wild V. vexillata was found in Java, Bali, Sumba, Flores and Timor, occasionally used as wild ‘forest food’, and cultivated V. vexillata was found in Bali and Timor, Seven cultivars were collected and two of these were made available for the National Botanic Garden of Belgium. The cultivars were primarily cultivated for their storage roots, propagated by seeds, required no scarified seeds for good germination and formed non-dehiscent pods. On-farm root yields of 18–30 t ha⁻¹ and seed yields of 0.7–1.2 t ha⁻¹ were estimated. A brief discussion about the common names of wild V. vexillata is given and it is proposed to use the name ‘tuber cowpea’ for V. vexillata accessions which are cultivated for their storage roots. The material may be of interest for regions, where the growing season is too short or the rainfall too low for sweet potato and cassava as well as to incorporate cultivar characteristics into wild V. vexillata accessions which are used for their storage roots.     

Relationships among different geographical groups,agro-morphology,fatty acid composition and RAPD marker diversity in Safflower (<Emphasis Type="Italic">Carthamus tinctorius</Emphasis>)

Patterns of geographical diversity, and the relationship between agro-morphological traits and fatty acid composition were assessed for 193 safflower (Carthamus tinctorius) accessions representing forty countries. Accessions were assigned to eight groups based on geographical proximity. Cluster and Principal Component analyses were performed to assess patterns of diversity among the accessions and to select the most distant accessions from each of eight groups for analysis of randomly amplified polymorphic DNA (RAPD) markers. There was a large amount of diversity for agro-morphological traits, fatty acid composition, and RAPD markers. Most correlations among different traits were rather low. Plant height showed a positive correlation with days to flowering (r = 0.63**). Palmitic acid was positively correlated with stearic acid and oleic acid values, and negatively correlated with linoleic acid (P < 0.01). Oleic acid and linoleic acid showed a strong negative correlation (r = −0.89**). The first three principal components together explained 59% of the variation, however, neither principal component analysis (PCA) nor marker analysis revealed a clear relationship between diversity pattern and geographical origin. Accessions from some geographical regions tended to group together, such as accessions from South Western Asia, Central Western Europe, and the Mediterranean region. The correlation between the morphological matrix and the genetic matrix based on RAPD markers was not significant (r = 0.027). Wide diversity in safflower germplasm indicates a considerable potential for improving this crop for both agronomic and quality traits.     

Evaluation of genetic diversity in Turkish melons (<Emphasis Type="Italic">Cucumis melo</Emphasis> L.) based on phenotypic characters and RAPD markers

The genetic relationships among 56 melon (Cucumis melo L.) genotypes collected from various parts of Turkey were determined by comparing their phenotypic and molecular traits with those of 23 local and foreign melon genotypes to investigate the taxonomic relationships and genetic variation of Turkish melon germplasm. Sixty-one phenotypic characters and 109 polymorphic RAPD markers obtained from 33 primers were used to define the genetic similarity among the melon genotypes by dendrograms or two and three dimensional scaling. There were high correlations (r ≥ 0.97) among the four resulting matrices used in molecular characterization. The correlations between phenotypic (Euclidean) and molecular Euclidean, Jaccard, Simple matching, and Nei analyses were r = 0.41, r = −0.40, r = −0.43 and r = −0.40, respectively. Related genotypes or genotypes collected from similar regions were partitioned to similar clusters. Both analyses (phenotypic and molecular) indicated that non-sweet melon types were dissimilar from sweet types and diversity of Turkish melon genotypes was higher than that of sweet foreign cultivars examined, but similar to that of the reference accessions employed. It was also observed that sweet Turkish melon genotypes belonging to groups inodorus and group cantalupensis were highly variable and could have intermated or have crossed with other non-sweet types.     

Comparative analysis of genetic diversity using molecular and morphometric markers in Andrographis paniculata (Burm. f.) Nees

Andrographis paniculata is a medicinal plant of immense therapeutic value. The present study was aimed to elucidate its genetic diversity based on morphochemical and RAPD markers from 53 accessions belonging to 5 eco-geographic regions. Analysis of variance and D ² statistics revealed significant differences in all the metric traits and sufficient inter-cluster distances indicating considerable diversity among the accessions. The complementary approach of RAPD was used to evaluate the genetic dissimilarities among all the accessions using 6 highly polymorphic primers. The average proportion of polymorphic loci across primers was 96.28%. The molecular genetic diversity based on Shannon index per primer averaged 5.585 with values ranging from 3.08 to 8.70 indicating towards wide genetic base. RAPD based UPGMA and D ² cluster analysis also revealed that various accessions available in different eco-geographic regions might have originated from native places of wild abundance. Similarity matrices were generated for molecular markers and morphometric data to determine the degree of congruence between the two. A highly significant but low correlation (r = 0.547, P < 0.001) was obtained thus implying the correspondence between the two. The species is hermaphroditic and a habitual inbreeder. The present study yielded a typical triangular congruence between its breeding system, morphometric traits and RAPD markers thus elucidating the usefulness of complementary approaches to make diversity analysis more explanatory and purposeful for optimum genetic amelioration and effective conservation of its genotypic variability.     

Impact of heavy metal amended sewage sludge on forest soils as assessed by bacterial and fungal biosensors

Bacterial and fungal bioluminescence-based biosensors were used as indicators of potential heavy metal toxicity to microorganisms in the needle litter of a mature Pinus radiata forest under heavy metal contaminated sewage sludge. Sewage sludge was amended with increasing concentrations of Cu, Ni and Zn and applied to the surface of a mature P. radiata forest. The response of the bacterial and fungal biosensors to soluble Cu, Ni and Zn in needle litter extracts was investigated. The bioluminescence response of the bacterial biosensor Escherichia coli HB101 pUCD607 declined as water-soluble Zn concentrations increased. The effective concentrations that gave a 50% reduction in bioluminescence (EC₅₀ values) for water-soluble Zn and total litter Zn were 1.3 mg l⁻¹ and 3700 mg kg⁻¹, respectively. The bioluminescence response of the fungal biosensor Armillaria mellea declined as soluble Cu concentrations increased. The EC₅₀ values for water-soluble Cu and total litter Cu were 0.12 mg l⁻¹ and 540 mg kg⁻¹, respectively. No decline in bioluminescence was noted for either the bacterial or fungal biosensor on exposure to increasing concentrations of water-soluble Ni. The use of a combination of bacterial and fungal biosensors offers a rapid and sensitive tool for assessing toxicity of heavy metals to microorganisms and, thus, elucidating the environmental impact of contaminants in sewage sludge on litter dwelling microorganisms.     

Response of maize to mycorrhizal colonization at varying levels of zinc and phosphorus

A greenhouse experiment was conducted in a red sandy loam soil (Alfisol) to study the responses of arbuscular mycorrhizal (AM) fungus Glomus intraradices Schenck & Smith inoculated (M+) and uninoculated (M−) maize (Zea mays L) plants exposed to various levels of P (15 and 30 mg kg⁻¹) and Zn (0, 1.25, and 2.5 mg kg⁻¹). Roots and shoots were sampled at 55 and 75 days after sowing and assessed for their nutritional status, root morphology, and root cation exchange capacity (CEC) besides grain quality. Mycorrhizal plants had longer and more extensive root systems than nonmycorrhizal plants, indicating that M+ plants are nutritionally rich, especially with P, which directly assisted in the proliferation of roots. Further, root CEC of M+ plants were consistently higher than those of M− plants, suggesting that mycorrhizal colonization assists in the acquisition of nutrients from soil solution. Mycorrhizal inoculated plants had significantly (P ≤ 0.01) higher P and Zn concentrations in roots, shoots, and grains, regardless of P or Zn levels. The available Zn and P status of AM fungus-inoculated soils were higher than unioculated soils. The data suggest that mycorrhizal symbiosis improves root morphology and CEC and nutritional status of maize plants by orchestrating the synergistic interaction between Zn and P besides enhancing soil available nutrient status that enables the host plant to sustain zinc-deficient conditions.     

Dynamic of organic matter in the heavy fraction after abandonment of cultivated wetlands

The abandonment of cultivated wetland soil increased the contents of light fraction organic matter (LFOM), heavy fraction organic matter (HFOM) and soil organic matter (SOM). The LFOM and HFOM content increased to 13.3 g kg⁻¹ and 62.4 g kg⁻¹ after 5 years whereas they were 8.4 and 47.9 g kg⁻¹ after 9 years of cropping, respectively. Fourteen years after abandonment, HFOM content increased to 104.3 g kg⁻¹. LFOM was positively correlated with HFOM (p < 0.001). A Langmuir equation was used to calculate the highest HFOM value. The value for the natural wetland soil was closed to this theoretical value (140.8 g kg⁻¹). After 14 years of abandonment, the HFOM maximum (HFOM_Max) value was lower than the equilibrium value suggesting that a further increase in HFOM can occur after abandonment. Assuming a linear accumulation (3.87 Mg C ha⁻¹yr⁻¹), it would take approximately 24 years after the abandonment to reach the HFOM_Max value.     

Nitrogen application effects on forage sorghum production and nitrate concentration

Abstract

Forage sorghum (Sorghum bicolor (L.) Moench) is an important annual forage crop but prone to high nitrate concentration which can cause toxicity when fed to cattle (Bos taurus and Bos indicus). Two field experiments were conducted over six site-years across Kansas to determine the optimum nitrogen (N) rate for no-till forage sorghum dry matter (DM) yield and investigate the effect of N fertilization on sorghum forage nitrate content. A quadratic model described the relationship between sorghum DM and N rate across the combined site-years. Maximum DM yield of 6530?kg ha^?1 was produced with N application rate of 100?kg N ha^?1. The economic optimum N rate ranged from 55 to 70?kg N ha^?1 depending on sorghum hay price and N fertilizer costs. Crude protein concentration increased with N fertilizer application but N rates beyond 70?kg N ha^?1 resulted in forage nitrate concentrations greater than safe limit of 3000?mg kg^?1. Nitrogen uptake increased with N fertilizer application but nitrogen use efficiency and N recovery decreased with increasing N fertilizer rates. In conclusion, forage sorghum required 55–70?kg N ha^?1 to produce an economic optimum DM yields with safe nitrate concentration.     

Crop residues and fertilizer nitrogen influence residue decomposition and nitrous oxide emission from a Vertisol

Crop residues with high C/N ratio immobilize N released during decomposition in soil, thus reducing N losses through leaching, denitrification, and nitrous oxide (N₂O) emission. A laboratory incubation experiment was conducted for 84 days under controlled conditions (24°C and moisture content 55% of water-holding capacity) to study the influence of sugarcane, maize, sorghum, cotton and lucerne residues, and mineral N addition, on N mineralization–immobilization and N₂O emission. Residues were added at the rate of 3 t C ha⁻¹ to soil with, and without, 150 kg urea N ha⁻¹. The addition of sugarcane, maize, and sorghum residues without N fertilizer resulted in a significant immobilization of soil N. Amended soil had significantly (P < 0.05) lower NO₃⁻–N, which reached minimum values of 2.8 mg N kg⁻¹ for sugarcane (at day 28), 10.3 mg N kg⁻¹ for maize (day 7), and 5.9 mg N kg⁻¹ for sorghum (day 7), compared to 22.7 mg N kg⁻¹ for the unamended soil (day 7). During 84 days of incubation, the total mineral N in the residues + N treatments were decreased by 45 mg N kg⁻¹ in sugarcane, 34 mg kg⁻¹ in maize, 29 mg kg⁻¹ in sorghum, and 16 mg kg⁻¹ in cotton amended soil compared to soil + N fertilizer, although soil NO₃⁻–N increased by 7 mg kg⁻¹ in lucerne amended soil. The addition of residues also significantly increased amended soil microbial biomass C and N. Maximum emissions of N₂O from crop residue amended soils occurred in the first 4–5 days of incubation. Overall, after 84 days of incubation, the cumulative N₂O emission was 25% lower with cotton + N fertilizer, compared to soil + N fertilizer. The cumulative N₂O emission was significantly and positively correlated with NO₃⁻–N (r = 0.92, P < 0.01) and total mineral N (r = 0.93, P < 0.01) after 84 days of incubation, and had a weak but significant positive correlation with cumulative CO₂ in the first 3 and 5 days of incubation (r = 0.59, P < 0.05).     

Greenhouse evaluation of EDTA effectiveness at enhancing Cd,Cr, and Ni uptake in <Emphasis Type="Italic">Helianthus annuus</Emphasis> and <Emphasis Type="Italic">Thlaspi caerulescens</Emphasis>

Background, Aims and Scope  Phytoremediation is a promising means for the treatment of heavy metal contamination. Although several species have been identified as hyperaccumulators, most studies have been conducted with only one metal. Experiments were conducted to investigate the ability of Helianthus annuus and Thlaspi caerulescens to simultaneously uptake Cd, Cr and Ni. Materials and Methods  The efficiency of plants grown in a sandy-loam soil was investigated. The ability of two EDTA concentrations (0.1 and 0.3 g kg⁻¹) for enhancing the phytoremediation of Cd, Cr and Ni at two different metal concentrations (24.75 mg kg⁻¹ and 90 mg kg⁻¹) was studied. Results   Thlaspi hyperaccumulated Ni with 0.1 g kg⁻¹ EDTA. When the EDTA dosage was increased to 0.3 g kg⁻¹, Thlaspi was able to hyperaccumulate both Ni and Cr. Since Thlaspi is a low-biomass plant, it was considered insufficient for full-scale applications. Helianthus annuus hyperacummulated Cr (with 0.1 g kg⁻¹ EDTA) and Cd (0.3 g kg⁻¹ EDTA). Discussion  When the contamination was 8.25 mg kg⁻¹ per metal, the total metal uptake was 10–25% (1.35 to 2.12 mg) higher and had the same uptake selectivity (Cr>>Cd>Ni) for both EDTA levels. It was hypothesized that complexation with EDTA interfered with Ni translocation. For these experiments, the optimal results were obtained with the H. annuus-0.1 g kg⁻¹ EDTA combination. Conclusions  Although the use of EDTA did increase the amount of metal that could be extracted, care should be taken during in-situ field applications. Chelators can also increase the amount of metals that are leached past the root zone. Metal leaching and subsequent migration could lead to ground water contamination as well as lead to new soil contamination. Recommendations and Perspectives  Additional research to identify the optimal EDTA dosage for field applications is warranted. This is necessary to ensure that the metals do not leach past the root zone. Identification of a plant that can hyperaccumulate multiple metals is critical for phytoremediation to be a viable remediation alternative. In addition to being able to hyperaccumulate multiple metals, the optimal plant must be fast growing with sufficient biomass to sequester the heavy metals.     

Extent and Pattern of Genetic Diversity for Morpho-agronomic Traits in Ethiopian Highland Pulse Landraces: I. Field Pea (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.)

An experiment was conducted in 2001 at Holetta and Kulumsa, Ethiopia, to study the extent and pattern of genetic diversity in Ethiopian field pea (Pisum sativum L.) landraces. One hundred forty-eight germplasm accessions were grown in an alpha lattice design with 2 replications. Data on 12 traits were collected and analyzed. Differences among the accessions were significant for most of the traits (except number of seeds/ pod) at each location even though differences pooled over location were mostly non-significant. The accessions were grouped into five clusters of different sizes. Accessions from the southern part of the country (Arsi) distributed overall clusters while those from the northern half (North and South Wello, North Gonder and North Shewa) fell into clusters C₁ to C₃. Cumulative effects of a number of characters dictated differentiation of the accessions into clusters. There was no definite relationship between geographic diversity and genetic diversity as overlapping was encountered in clustering pattern among accessions from different parts of the country. Accessions from different regions might have similar genetic background and those from the same origin might also have different genetic background. Therefore, geographic diversity should not necessarily be used as an index of genetic diversity and parental selection should be based on a systematic study of genetic diversity in a specific population. Genetic distances among most of the clusters were significant that crosses between parents selected out of them are expected to generate desirable genetic recombination. Selection should also consider the special advantages of each cluster and each accession within a cluster. Future germplasm collection, conservation and breeding efforts should focus not only on inter-regional diversity but also on intra-regional diversity.     

Development of Core Collection in Pigeonpea [<Emphasis Type="Italic">Cajanus cajan</Emphasis> (L.) Millspaugh] using Geographic and Qualitative Morphological Descriptors

Pigeonpea is an important pulse crop grown by smallholder farmers in the semi-arid tropics. Most of the pigeonpea cultivars grown to date are selections from the landraces, with a narrow genetic base. With the expansion of the crop to newer areas, problems of local importance are to be addressed. Hence, an economically feasible and faster germplasm evaluation mechanism, such as a core collection, is required. This article describes the development of core collection from 12,153 pigeonpea accessions collected from 56 countries and maintained at ICRISAT, Patancheru, India. The germplasm accessions from 56 countries were placed under 14 clusters based primarily on geographic origin. Data on 14 qualitative morphological traits were used for cluster formation by Ward’s method. From each cluster ≈10% accessions were randomly selected to constitute a core collection comprising 1290 accessions. Mean comparisons using Newman–Keuls test, variances’ comparisons by Levene’s test, and comparison of frequency distribution by χ²-test indicated that the core collection was similar to that of the entire collection for various traits and the genetic variability available in the entire collection is preserved in the core collection. The Shannon–Weaver diversity index for different traits was also similar for both entire and core collection. All the important phenotypic associations between different traits available in the entire collection were preserved in the core collection. The core collection constituted in the present study facilitates identification of useful traits economically and expeditiously for use in pigeonpea improvement.     

Soil nitrogen distribution and deposition on shortgrass prairie adjacent to a beef cattle feedyard

Cattle feedyards can impact local environments through emission of ammonia and dust deposited on nearby land. Impacts range from beneficial fertilization of cropland to detrimental effects on sensitive ecosystems. Shortgrass prairie downwind from an adjacent feedyard on the southern High Plains of Texas, USA changed from perennial grasses to annual weeds. It was hypothesized that N enrichment from the feedyard initiated the cascade of negative ecological change. Objectives were to determine the distribution of soil nitrogen and estimate N loading to the pasture. Soil samples were collected from 119 locations across the pasture and soil total N (TN), nitrate-N and ammonium-N (AN) determined in the top 30 cm. Soil TN concentration decreased with distance downwind from the feedyard from 1.6 ± 0.2 g kg⁻¹ at 75 m to 1.2 ± 0.05 g kg⁻¹ at 582 m. Nitrate-N concentration decreased within 200 m of the feedyard and changed little at greater distances. Ammonium-N concentration decreased linearly (P < 0.001) with increasing distance from the feedyard from 7.9 ± 1.7 mg kg⁻¹ within 75 m from the feedyard to 5.8 ± 1.5 mg kg⁻¹ at more than 550 m from the feedyard; however, distance only explained 12% of the variability in AN concentration. Maximum nitrogen loading, from 75 to 106 m from the feedyard, was 49 kg ha⁻¹ year⁻¹ over 34 years and decreased with distance from the feedyard. An estimate of net dry deposition of ammonia indicated that it contributed negligibly to N loading to the pasture. Nitrogen enrichment that potentially shifted vegetation from perennial grasses to annual weeds affected soil N up to 500 m from the feedyard; however, measured organic and inorganic N beyond that returned to typical and expected levels for undisturbed shortgrass prairie.

Patterns of phenotypic diversity for phenologic and qualitative traits in Ethiopian tetraploid wheat germplasm

A total of 4,840 entries of tetraploid wheat germplasm collections representing 121 accessions from Ethiopia were evaluated for phenologic and qualitative trait diversity. The objectives were to assess the diversity patterns of the germplasm with respect to regions, species and altitudinal class. High values of Shannon–Weaver Diversity Index (H′) were recorded for most traits in each region, altitudinal classes, and species. Monomorphism was also high at accession levels. Both H′ and Nei’s gene diversity value for the entire data set (total gene diversity H _T = 0.572; the within accessions gene diversity H _S = 0.112; and gene diversity among accessions D _ST = 0.460) showed the variation for the trait is mainly among accessions/populations rather than within accessions/population. The least mean H′ value over all the traits used for the study was obtained from released varieties (among the origin groups) and Triticum dicoccon (among species). Triticum durum exhibit the highest H′ for a number of traits. Accessions collected from altitudinal class III (2401–2800 m a.s.l.) and class II (2001–2400 m a.s.l.) showed the highest H′ values for a valuable number of traits. Thus classifications using various phenology and qualitative traits enable to identify adaptation of a genotype and would improve the evaluation of genotype for potential adaptation.     

Mercury evolution (1978–1988) in fishes of the La Grande hydroelectric complex,Quebec, Canada

From 1978 to 1988, the evolution of the Hg content of fish has been monitored in the areas affected by the La Grande hydroelectric complex. Four fish species were considered: two non piscivorous, lake whitefish (Coregonus clupeaformis) and longnose sucker (Catostomus catostomus), and two piscivorous, northern pike (Esox lucius) and walleye (Stizostedion vitreum). The evolution of Hg concentrations in time depends upon fish species and type of reservoirs. Non piscivorous fish react more rapidly than piscivorous. Five years after filling, their Hg level had increased by a factor of four in reservoirs with rapid filling and short renewal rate; levels decreased thereafter. In the La Grande 2 reservoir, the Hg concentration of 400 mm lake whitefish went from 0.16 mg kg⁻¹ before impoundment to 0.57 mg kg⁻¹ 5 yr after filling, and then started to decrease. For 700 mm northern pike, the Hg level went from 0.61 mg kg⁻¹ to 2.99 mg kg⁻¹ and was still increasing 9 yr after initial filling. In reservoirs where filling spans over a few years or with long renewal rate, their Hg content evolves more slowly. In river sections located downstream from reservoirs, the Hg content of non piscivorous species was significantly higher than in reservoirs. In 1988, whitefish exhibited values of 1.22 mg kg⁻¹ in the tailwater of the La Grande 2 power station, compared to 0.48 mg kg⁻¹ in the forebay. This phenomenon could be related to the drift of food organisms from the upstream reservoir. A study of several reservoirs of the Canadian Shield, which were created between 6 and 67 yr ago suggests that it could take between 20 and 30 yr before Hg concentration in fish return to preimpoundment levels.