Diversity of the Sheanut tree (Vitellaria paradoxa C.F. Gaertn.) in Ghana

The Sheanut tree (Vitellaria paradoxa C.F. Gaertn.) is highly valued for oil obtained from its seeds and frequently maintained in the semi-arid parklands of sub-Saharan Africa from Senegal to Uganda. Although variation has been noted for V. paradoxa subsp. paradoxa, few studies have been undertaken on patterns of phenotypic or genotypic diversity. Results are presented from 294 accessions collected in Ghana, using easily quantifiable morphological parameters. Productive mature trees varied from shrubby multi-stemmed individuals (height <5 m) to 30-m straight-boled trees with high compact canopies. The leaf lamina (tree mean ±% coefficient of variation of total mean) varied from 9.2 to 22.5 cm (±15.0%); seed length from 1.74 to 3.74 cm (±11.7%); and fat content from 29.1 to 61.9% of dry kernel weight (±9.4%). Clinal trends significantly correlated with location parameters that in turn related to environmental variation. Population variation of seed characteristics increased to the Northeast, perpendicular to the annual movement of the inter-tropical convergence zone. It is proposed that this is a consequence of past climatic changes, coupled with a lack of methodical selection for seed type when trees are maintained on agricultural land. Isozyme analysis revealed moderate to high levels of heterozygosity (He 0.2142) and high geneflow (Fst = 0.0124, Nm = 19.9), supporting results obtained from morphological studies. Isozyme and multivariate morphology analyses showed similar but weak geographical separation patterns.     

Nutrient release from decomposing leaf mulches of karité (Vitellaria paradoxa) and néré (Parkia biglobosa) under semi-arid conditions in Burkina Faso, West Africa

Information on decomposition and nutrient release from leaf litter of trees in agroforestry parkland systems in Sub-Saharan Africa is scarce despite the significant role of these trees on soil fertility improvement and maintenance. Decomposition and nutrient release patterns from pruned leaves of the two most common species of parklands of the semi-arid zone of West Africa: Vitellaria paradoxa C.F. Gaertn (known locally as karité) and Parkia biglobosa (Jacq.) Benth. (known locally as néré), were investigated by a litter-tube study in Burkina Faso. Litter quality, methods of leaf exposure to the soil and combination with fertilizers were the factors studied. Leaves of néré had a higher nutrient content (C, N, P, Ca) and contained more ash and lignin than leaves of karité. Karité leaves had a greater content of K, cellulose and polyphenols. The pruned leaves of karité and néré showed two distinct decomposition patterns. Néré leaves decomposed more rapidly, with less than 32% of the initial weight remaining after the rainy season (4 months) while karité leaves decomposed more slowly with 43% of the leaf litter remaining after the rainy season. Addition of urea and compost did not significantly affect the rate of decomposition. Significant interaction was observed between species and method of leaf exposure for the first sampling date. Leaf litter of néré buried in soil gave the highest weight loss (34% of the initial mass in 1 month) compared with exposed leaf litter of néré and karité, and buried leaf litter of karité. Except for N, nutrient release patterns were similar for both species but the nutrient release rates were higher for néré leaves compared with karité leaves. N was immobilised in karité leaves most likely due to low N and high phenolic content. The rate of nutrient release from karité leaves followed the general trend K>P>N.     

Reduced effective population size in an overexploited population of the Nile crocodile (Crocodylus niloticus)

Unchecked exploitation of wildlife resources is one of the major factors influencing species persistence throughout the world today. A significant consequence of exploitation is the increasing rate at which genetic diversity is lost as populations decline. Recent studies suggest that life history traits affecting population growth, particularly in long-lived species, may act to moderate the impact of population decline on genetic variation and lead to remnant populations that appear genetically diverse despite having passed through substantial demographic bottlenecks. In this study we show that the retention of genetic variation in a partially recovered population of Nile crocodile is deceptive, as it masks the reality of a significant decline in the population’s effective size (N_e). Repeated episodes of unchecked hunting in the mid to late 20th century have today led to a five-fold decrease in the population’s N_e. Using current census data we estimate the contemporary N_e/N ratio as 0.05 and, in light of quotas that permit the ongoing removal of adults, simulated the likely effects of genetic drift on extant levels of variation. Results indicate that even if the current effective size is maintained, both allelic diversity and heterozygosity will decline. Our findings have complex implications for long-lived species; an emphasis on the retention of genetic variation alone, whilst disregarding the effects of population decline on effective size, may ultimately obscure the continued decline and extinction of exploited populations.     

Unexpected high levels of genetic variability and the population structure of an island endemic rodent (Oryzomys couesi cozumelae)

Oryzomys couesi cozumelae is an endemic, threatened rodent from Cozumel Island, Mexico. We estimated its genetic diversity and structure by analyzing microsatellite loci in 228 samples from 12 sampling sites widely distributed throughout the island. Unexpected high levels of genetic and allelic diversity were found: a total of 54 alleles, an average of 10.8 alleles per locus, and high heterozygosity values (mean H_O = 0.624, H_E = 0.690 and H_Nei = 0.689). These values are higher than those reported for small sized insular mammals, higher than that found in 37 individuals of the mainland O. couesi from southern Mexico (H_O = 0.578) that we analyzed for comparative purposes, and similar to those of other mainland small mammal populations. Despite factors that affect Cozumel’s biota, such as exotic predators and competitors, hurricanes, seasonal population fluctuations and anthropogenic activities, no evidence of genetic bottlenecks was found. A significant population structure was observed and a model of isolation-by-distance was supported. Our findings render O. c. cozumelae a high conservation value, not only for its high genetic diversity and structure, but because available data suggests that its population has declined significantly in recent years. Further habitat fragmentation and population isolation could result in a higher genetic structure and loss of genetic diversity. The protection of habitat, the maintenance of habitat connectivity and the removal of introduced competitors and predators are a conservation priority. Acknowledging that the genetic structure of populations has crucial conservation implications, the present genetic information should be taken into account in management plans for the conservation of O. c. cozumelae.     

Physiological evidence for reproductive suppression in the introduced population of brown tree snakes (Boiga irregularis) on Guam

Introduced species are an increasingly pervasive problem. While studies on the ecology and behavior of these pests are numerous, there is relatively little known of their physiology, specifically their reproductive and stress physiology. One of the best documented introduced pest species is the brown tree snake, Boiga irregularis, which was introduced onto the Pacific island of Guam sometime around World War II. The snake is responsible for severely reducing Guam's native vertebrates. We captured free-living individuals throughout the year and measured plasma levels of stress and sex hormones in an effort to determine when they were breeding. These data were compared to reproductive cycles from a captive population originally collected from Guam. Free-living individuals had chronically elevated plasma levels of the stress hormone corticosterone and basal levels of sex steroids and a remarkably low proportion were reproductively active. These data coincide with evidence that the wild population may be in decline. Captive snakes, had low plasma levels of corticosterone with males displaying a peak in plasma testosterone levels during breeding. Furthermore, we compared body condition between the free-living and captive snakes from Guam and free-living individuals captured from their native range in Australia. Male and female free-living snakes from Guam exhibited significantly reduced body condition compared to free-living individuals from Australia. We suggest that during the study period, free-living brown tree snakes on Guam were living under stressful conditions, possibly due to overcrowding and overexploitation of food resources, resulting in decreased body condition and suppressed reproduction.     

Genetic diversity in the Olive tree (Olea europaea L. subsp. europaea) cultivated in Portugal revealed by RAPD and ISSR markers

To assess the genetic diversity of the most important olive cultivars used in Portugal, a base collection was established with two hundred and one accessions of eleven cultivars from the different agro-ecological-regions (AER) of olive oil production. Inter-cultivar diversity was evaluated using seven RAPD primers producing fifty-nine polymorphic markers that enable cultivar distinction. Discriminant analysis according to fruit use and AER revealed a genetic structure associated with local selection both for fruit exploitation and agro-ecological adaptation. Intra-cultivar diversity of the ancient cultivar Galega was also investigated. Three RAPD and five ISSR primers produced ninety-three polymorphic markers upon seventy-seven accessions from five AERs. Total accession discrimination was achieved. UPGMA clustering and discriminant analysis revealed that the genetic diversity was predominantly structured according to accessions origin. The within and among AER variation revealed by AMOVA supported this genetic structure and showed a high proportion of intra-AER variability. These evidences suggest that Galega is composed by a mixture of different genotypes adapted to local conditions, indicating that this cultivar is in an early stage of domestication and should be treated as a landrace instead of a uniform cultivar. The assessment of Galega genetic diversity within each of the five AERs indicated the highest significant level (H_g = 6.23 at p< 0.001) in Ribatejo-Santarém. This finding associated with the distinctiveness of Galega in relation to other Portuguese cultivars and with the recent insights of olive tree domestication allowed us to hypothesize that Ribatejo-Santarém was the ecological region of origin and dispersion of this ancient cultivar.     

Microsatellite diversity and effective population size in a germplasm bank of <Emphasis Type="Italic">Hymenaea courbaril</Emphasis> var. <Emphasis Type="Italic">stilbocarpa</Emphasis> (Leguminosae), an endangered tropical tree: recommendations for conservation

Deforestation in southeast Brazil has led to the extinction of Hymenaea courbaril var. stilbocarpa and ex situ conservation has been established. In this study, the levels of genetic diversity and the effective population size of H. courbaril in a germplasm bank were investigated using six nuclear microsatellite loci. A total of 79 and 91 alleles were found in 65 seed-trees and their 176 offspring, respectively. Offspring have a higher average number of alleles per locus (A = 15.2) than seed-trees (A = 13.2), but lower observed heterozygosity (offspring: H _o = 0.566; seed-trees: H _o = 0.607). The estimate of outcrossing rate shows that the study population is perfectly outcrossed (t _m  = 0.978, P > 0.05). Significant deviations from random mating were detected through mating among relatives and correlated matings. The average variance in effective population size for each family was 2.63, with a total effective population size retained in the bank of 170.1. These results confirm that the preserved population of H. courbaril retains substantial genetic variability. Moacyr Antonio Mestriner and Ana Lilia Alzate-Marin—CEEFLORUSP Members.     

Analysis of korarima (<Emphasis Type="Italic">Aframomum corrorima</Emphasis> (Braun) P.C.M. Jansen) indigenous production practices and farm based biodiversity in southern Ethiopia

Korarima (Aframomum corrorima (Braun) P.C.M. Jansen) production is declining mainly due to destruction of the plant’s natural habitat. A survey was conducted in the three major korarima growing administrative zones, Gamo Gofa, Debub Omo and Kaffa in southern Ethiopia to assess indigenous production practices, wealth status, farm based biodiversity and household characteristics using participatory rural appraisal (PRA) and semi-structured questionnaires. The wealth is unevenly distributed among households and not significantly different for korarima growers and non-korarima growers. Farmers acknowledged that shortage of shade trees; low yield and lack of improved varieties had contributed to decrease in production area (PA). A total of three distinct named korarima landraces were recorded, with a range from one to three on individual farms implying low farm based biodiversity. More households grew enset (Ensete ventricosum (Welw.) Cheesman) in Gamo Gofa and Kaffa while maize (Zea mays L.) was grown by nearly all households in Debub Omo. Only a few households grew korarima. Most of the household characteristics significantly affected the PA of korarima. The correlation coefficients indicated that the relationship of household characteristics were significant. Findings of this study suggest that the maintenance of shade trees on the main farm field is the main requirement for korarima production.     

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.     

Over-exploitation and lack of protection is leading to a decline of a protected calcicolous tree species Excentrodendron hsienmu (Tiliaceae) in China

Excentrodendron hsienmu (W. Y. Chun and K. C. How) H. T. Chang and R. H. Miau (Tiliaceae) is a protected species in China but little is known about its present status in the field. The natural regeneration is satisfactory but the age structure of hsienmu forests is highly biased as a result of selective felling of young trees and large trees. Large hsienmu trees are used to make chopping blocks and young trees are cut as fuelwood; both these uses are contributing to the decline in population. Despite being a protected species, it appears that no official concrete protection measures have been adopted. Illegal felling of big trees has continued and cutting of young trees as fuelwood is common, especially in forests far from villages. In areas close to villages or that are difficult to access, hsienmu forests are mostly protected. A ban on tree felling and on the sale of chopping blocks made from hsienmu wood, and closure of hsienmu forests to human intervention, would help to protect this important tree species, but the local population need to be provided with alternative options for income generation and fuel in order for protection measures to be accepted and have a chance of success.     

Conservation of the genetic variation of Triticum tauschii (Coss.) Schmalh. (Aegilops squarrosa auct. non L.) in synthetic hexaploid wheats (T. turgidum L. s.lat. x T. tauschii; 2n=6x=42, AABBDD) and its potential utilization for wheat improvement

Triticum tauschii (Coss.) Schmalh. (Aegilops squarrosa auct. non L., 2n=2x=14, DD genome) with its diverse range of accessions and distribution provides a unique opportunity for exploiting novel genetic variability for wheat (T. aestivum L.) improvement associated with biotic/abiotic stress factors. From our working collection of 490 T. tauschii accessions we have so far produced 430 different synthetic hexaploids (2n=6x=42, AABBDD) resulting from the chromosome doubling of Triticum turgidum L. s. lat. x T. tauschii F₁ hybrids (each synthetic involving a different T. tauschii accession). We present here our results on hybrid production, plantlet regeneration, cytology, colchicine induced doubling of the 2n=3x=21 chromosome F1 hybrids, seed increase of the doubled progeny and screening for a biotic stress; Cochliobolus sativus Ito and Kuribay (syn. Helminthosporium sativum Pamm. King and Bakke); of 250 of these synthetic hexaploid (2n=6x=42) amphiploids. Application of the direct crossing methodology involving susceptible T. aestivum cultivars with resistant T. tauschii accessions is also alluded to.     

Cultivation of lotus (<Emphasis Type="Italic">Nelumbo nucifera</Emphasis> Gaertn. ssp. <Emphasis Type="Italic">nucifera</Emphasis>) and its utilization in China

Lotus (Nelumbo nucifera Gaertn. ssp. nucifera), one of 12 aquatic species used as vegetable, has been cultivated for more than 2,000 years, and now has been widely cultivated in almost all provinces in China. The largest area under cultivation of lotus is located in the regions surrounding mid-down Yangtse River, including Hubei, Jiangsu, Zhejiang, Anhui, Jiangxi and Hunan provinces. According to different purposes or morphological differences, the Chinese lotus (N. nucifera ssp. nucifera) is usually classified into three types: rhizome lotus, seed lotus and flower lotus. Rhizome lotus is mainly cultivated in Hubei, Jiangsu, Anhui and Zhejiang provinces; Seed lotus in Jiangxi, Fujian and Hunan, and flower lotus in Wuhan, Hubei province, and Beijing. Up to the year 2002, a total of 572 lotus accessions (including landraces, cultivars and breeding lines) were conserved in National Garden of Aquatic Vegetable, Wuhan, Hubei province, including those collections from 153 counties in 18 provinces, and lines bred by breeders. Out of these accessions, 310 were rhizome lotus which contains 201 landraces and 109 breeding lines; 229 were flower lotus including 172 cultivars and 57 breeding lines; and the rest 33 were seed lotus with 18 cultivars.     

Continuous defoliation of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) and associated changes in the composition and activity of the microbial population of an upland grassland soil

A microcosm study was conducted to investigate the effect of continuons plant defoliation on the composition and activity of microbial populations in the rhizosphere of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). Continuons defoliation of ryegrass and clover resulted in sigmficant (P <0.01) increases in soil microbial biomass, although whilst increases were measured from day 2 in soil sown with clover significant increases were only seen from day 21 in soil sown with ryegrass. These increases were paralleled, from day 10 onwards, by increases in the numbers of culturable bacteria. Numbers ofPsendomonas spp. also increased in the later stages of the study. No influence on culturable fungal populations was detected. Whilst shifts in the composition of the microbial populations were measured in response to defoliation there was little effect on microbial activity. No changes in either dehydrogenase activity or microbial respiration in the rhizosphere of ryegrass or clover were measured in response to defoliation, but both dehydrogenase activity and microbial respiration were greater in ryegrass than clover when values over the whole study were combined. Continuous defoliation resulted in significant (P <0.001) reductions in the root dry weight of ryegrass and clover, of the order 19% and 16%, respectively.     

Chromosomal distribution and genetic expression of Lophopyrum elongatum (Host) A. Löve genes for adult plant resistance to stripe rust in wheat background

A set of wheat cv. Chinese Spring (CS)-Lophopyrum elongatum addition and substitution lines has been analyzed for its potential to offer new sources of stripe rust resistance for wheat. The adult plants of these lines, together with CS-L. elongatum amphiploid and CS, were inoculated by new physiological races CYR-30 and CYR-31 of stripe rust in China. The resistance investigation indicated that chromosome 7E1 of L. elongatum was responsible for the adult resistance in CS background. Moreover, the expression of the adults plant resistance derived from chromosome 7E1 in wheat background was dependent on the wheat genotype. In addition, the different rust resistance and glutenin composition were observed in 2 CS-L. elongatum amphiploids, indicating the genetic diversity existed in different origins of L. elongatum.     

Variation in morphology and seed production of snow clover [<Emphasis Type="Italic">Trifolium pratense</Emphasis> L. subsp. <Emphasis Type="Italic">nivale</Emphasis> (Koch) Arcang.] germplasm from the Rhaetian Alps,Italy

A recent approach to restoration of degraded mountain landscapes (e.g. ski slopes) recommend to sow seed mixtures including ‘site-specific’ species, i.e. native germplasm adapted to the prevailing conditions and ecologically compatible with the area of intervention. To better exploit the potential of these species and enhance their spread in revegetation projects, deeper knowledge is needed, however, on the existing variation in their germplasm, particularly for economically useful traits such as seed yield. Snow clover is one of the recommended ‘site-specific’ legumes. This study evaluated 12 populations of snow clover, collected in three valleys of the Rhaetian Alps, Italy, to assess their variation and highlight any promising material. The evaluation encompassed a mountain and a lowland site, to verify the behaviour of the germplasm also in one environment markedly different from that of origin. Differences among valleys were observed for flower colour, growth habit and type, flowering time and susceptibility to mildew, although the overall pattern of phenotypic diversity was similar among valleys. Some effect of the evaluation site on the expression of morphological and seed production traits, and on the overall diversity, was also evident. Furthermore, the lowland site experienced very high plant mortality towards the end of the first growing season. Individual populations proved a valuable source of variation for seed production. Some populations, in particular, were worth of attention for a possible selection of high-seed-yielding snow clover cultivars. An assessment of the mating system suggested a lack of self-tripping or an almost absolute self-incompatibility in snow clover.