Genetic Erosion

One concern in the ongoing debate over the conservation status of mahogany has been the possibility that selective logging, as a form of negative phenotypic selection, might have led to deterioration in the genetic quality of populations. The incidence and degree of such ‘dysgenic’ effects is discussed, based on a consideration of mahogany logging practices, their expected genetic effects and empirical data on phenotypic selection in forest trees. Loggers have tended to avoid diseased, small, very large and poorly-formed individuals, and consequently logging has tended to increase the proportion of poor quality phenotypes relative to that before logging; in at least some conditions, selection differentials have been strongly negative. However, the upper limit for heritability of logger-selected traits in naturally-regenerated mahogany is probably no more than c. 0.1. Consequently, and assuming relatively extreme but realistic negative selection differentials of 50%, the maximum nega...

The demands for increasing global crop production have prompted the development of new approaches relying on molecular marker technologies to investigate and improve the plant genome. The merits of molecular markers make them valuable tools in a range of research areas. This review describes novel approaches based on modern molecular marker technologies for characterization and utilization of genetic variation for wheat improvement. Large-scale genome characterization by DNA-fingerprinting has revealed no declining trends in the molecular genetic diversity in wheat as a consequence of modern intensive breeding thus opposing the genetic ‘erosion’ hypothesis. A great number of important major genes and quantitative trait loci have been mapped with molecular markers. Marker-assisted selection based on a tight linkage between a marker allele and a gene(s) governing a qualitative or quantitative trait is gaining considerable importance as it facilitates and accelerates cultivar improvement through precise transfer of chromosome regions carrying the gene of interest. The implementations of molecular markers in wheat genotyping, mapping and breeding complemented by specific approaches associated with the complex polyploid nature of common wheat are analyzed and presented.

At the beginning of the 20th Century Italy was one of the most important producers of lentil in the Mediterranean basin. Presently, this pulse is mainly cultivated in marginal areas of Central and Southern Italy and in some small islands. As a result of the reduced attention devoted to lentil, several autochthonous populations have disappeared together with the traditions related

Plant genetic resources are one of the most important tools in agricultural research and development for the improvement of the productivity and sustainability of production systems, both in the developed and the developing world. There used to be plenty of diversity among crop varieties and their wild relatives, but this is rapidly disappearing, due to a trend towards uniformity in

Directed selection for economically desirable traits can lead to genetic erosion of individual breeds. A genetic base thus diminished is likely to limit the potential for improving production characteristics that may be vital for sustainable agricultural systems in the future. According to the FAO inventory 55% of the world’s pigs are located in the Asian and Pacific region, representing 37% of the breeds listed by the FAO (Scherf, 2000). A number of studies have been conducted on the genetic diversity of European (Laval et al., 2000) and Chinese pig breeds (Li et al., 2000) and a new international cooperation project has been started recently to evaluate 50 Chinese breeds in comparison with 59 European breeds (Blott et al., 2003). Polymorphic molecular genetic markers provide a means of assessing within and between breed genetic diversity. Micro satellite markers are recommended for studies of livestock diversity due to their abundant and even distribution throughout the genome, high polymorphism and comparative ease of genotyping. They have been used to characterise a wide variety of farm animal breeds in several species. This study is concerned with the evaluation of 10 micro satellite markers in five Vietnamese indigenous pig breeds with a diverse geographical origin, the assessment of their level of genetic diversity and the estimation of genetic distances among them.

El objetivo de esta investigación fue analizar los mayores impactos causados por la industria del banano tales como la afectación a los ecosistemas naturales por el aumento constante de las zonas de cultivo que afectan la diversidad propiciando la erosión genética de muchas especies endémicas, cuyos habitad son destruidos al momento de  establecer monocultivos de banano, junto con la utilización indiscriminada de agroquímicos. Para desarrollar este estudio se realizó una investigación bibliográfica a partir del análisis de artículos científicos, análisis de datos y metadatos de organismos internacionales y gubernamentale referentes a zonas de vegetación afectadas por la industria del banano. Los resultados de estos análisis nos permiten concluir que la industria bananera ha presentado una demanda de su producción en aumento exponencial en los mercados internacionales hasta los actuales momentos, justificado por la calidad de la fruta que se obtiene gracias a las condiciones ecogeográficas favorables que presentan las zonas bananeras en Ecuador, especialmente la zona sur comprendida por los cantones Machala, Pasaje, El Guabo, Sta. Rosa y Arenillas en la Provincia de El Oro.

In Tunisia, the local germplasm of wild Gladiolus have been currently damaged by severe genetic erosion, pollution, urbanization and bad farming practices. The aim of the present study was to prospect, collect and assess morphologically 15 accessions of this species from several areas in Tunisia. The identification and characterization of 300 individuals (20 samples per each accession), was performed utilizing 20 morphological traits. In this study, morphological traits showed a large variability for wild Gladiolus species. Cluster analysis revealed two major clusters: the first includes the accessions with populations of Gladiolus italicus, the second consists of all the rest, the populations with seeds wing. The Principal Component Analysis of the measured
morphological characters revealed that the 3 primary components included 70.5% of total variability. The diversity is currently threatened by genetic erosion. The sustainability of Gladiolus in Tunisia is necessary using a rapid program of conservation in situ and ex situ.

This study was motivated by the realisation that although public and civil society projects interventions emphasize dairy intensification, dairy producers adopt systems that exhibit a continuum of intensification stretching from extensive to intensive levels. De-intensification of zero grazing, downgrading of herds in other grazing systems and adoption of extensive or intensive systems on farmers' own accord have been observed. The purpose of this study was to examine enterprise choices and resource allocation in different dairy systems under traditional (observed) and optimum (profit driven) scenarios. Longitudinal data used was obtained from 14 representative farms for zero grazed, tethered, herded, semi-intensive and fenced dairy systems in Masaka, Mbarara and Jinja districts. Observed and profit driven farm plans were assessed by whole-farm modeling using Linear Programming net farm benefit maximization. Results obtained show that net farm benefits were significantly higher ...

Enset (Ensete ventricosum) production is declining, and it faces genetic erosion due to drought, diseases and population pressure. Participatory Rural Appraisal (PRA) and additional formal survey studies on 315 households were conducted over three consecutive years (1998–2000) in the Sidama, Wolaita and Hadiya ethnic regions of southern Ethiopia to assess traditional cultivation methods, analyse the production systems, and evaluate farm-based enset biodiversity. The regions differ in terms of cultural background, resources, farming systems, population density, and agro-ecology. Furthermore, the methods for initiating suckers and the frequency of transplanting vary among the three regions.Diverse enset landraces were identified in the Sidama (52), Wolaita (55) and Hadiya (59) regions. Sidama farmers had the highest number of landraces per farm, 57% and 21% more than found on Wolaita and Hadiya farms respectively. In all three regions, landrace diversity was influenced by household re...

Etnoagronomy is becoming a new discipline that studies the traditional agrosystems, serving the needs that agroecology has to interpret the keys of traditional agriculture to be applied to modern agriculture. The recent development of the discipline requires that as we try to retrieve all the possible information we will develop the tools for its implementation. Likewise the attempts to measure the level of genetic erosion of the traditional agrosystems has exposed the difficulty of combining ecological parameters with socioeconomic parameters that are pertinent when dealing with agrodiversity. In this regard the development of certain indicators such as the Frequency of Appearance in a Plantation, the Importance for Species and the Use of Vernacular Names, contribute quantitative data that facilitates comparison and measurement of certain phenomena, such as the genetic erosion, when we carry out a diachronic analysis.

La Etnoagronomia se ha venido consolidando como una nueva disciplina que aborda el estudio de los agrosistemas tradicionales, sirviendo de apoyo a las necesidades que la Agroecologia tiene de interpretar las claves de la agricultura tradicional para aplicarlas a la agricultura de la actualidad. El reciente desarrollo de la disciplina obliga a que, a la vez que intentamos recuperar la mayor cantidad posible de informacion, desarrollemos las herramientas a emplear. Igualmente los intentos de medir el nivel de erosion genetica de los agrosistemas tradicionales ha puesto de manifiesto la dificultad de combinar parametros ecologicos con parametros socioeconomicos que son primordiales al tratar la agrodiversidad. En esa medida el desarrollo de ciertos indices como son los de Frecuencia de Cita de un Cultivar, de Importancia por Especie, y de Uso de Nombres Vernaculares, aportan datos cuantitativos que permiten realizar comparaciones y medir la intensidad de ciertos fenomenos, como la eros...

Lima bean (Phaseolus lunatus L.) is an important crop in traditional Mayan agriculture of the Yucatan Peninsula, Mexico, its Mesoamerican center of diversity. Genetic erosion in this species is currently a threat in this region out of 3 of 21 landraces dominate 71.24% of the cultivated area, and 12 are rare landraces grown only in 6.29%. Using 90 ISSR loci, we estimated the diversity and genetic relationships for 21 landraces to analyzing their risk of genetic erosion, and generate data for their in situ conservation. Total genetic diversity was high (h = 0.29), however it was lower than wild gene pool reported (h = 0.69). The abundant landraces had genetic diversity values lower (h = 0.13, I = 0.17) than the common (h = 0.26, I = 0.33) and rare landraces (h = 0.24, I = 0.27). However, the rare landraces are in a higher risk of genetic erosion due to local extinction. The cluster analysis showed no groups corresponding to morpho-phenological characteristics, geographic origin or traditional classification, which resulted from high inter-landraces gene flow levels. The molecular data confirmed that the domesticated Lima bean pool of the Yucatan Peninsula has a high risk of genetic erosion. If current tendencies in landrace cultivation continue, many will no longer be planted within two to three generations, with a consequent loss of their alleles. Programs urgently need to be established for in situ conservation of Lima bean landraces in this region.

The Tunari National Park is located in the Tunari Mountain Range, part of the Cochabamba Range in the Bolivian Andes. The Park is home to species of wild potato (Solanum section Petota Solanaceae), but these are now threatened by human activity. The aims of the present study were: 1) to determine the distribution of wild potato species in the Park, and, 2) to determine the size of their populations. Collection routes were established within the Park, and the species present along them recorded in 2006, 2007 and 2008. Their population sizes were determined in 2008. Four wild potato species were identified: S. capsicibaccatum, S. berthaultii, S. brevicaule and S. toralapanum. S. capsicibaccatum was the most abundant and had the most extensive distribution, followed by S. berthaultii; these last two species are likely endemic. The other species, although probably also endemic, were much less widely distributed; some limiting factor(s) would therefore appear to be acting upon them. S. berthaultii showed variations in corolla shape (rotate, pentagonal and semi-stellate) and flower colour (whitish-lilac to blue-lilac). The remaining species showed no apparent intraspecific variation in their morphological characteristics.

In continuation of collecting missions in the last five years a further mission has been carried out in South Italy jointly by staff members of the Istituto del Germoplasma, Bari, and the Zentralinstitut für Genetik und Kulturpflanzenforschung, Gatersleben, in September/October 1985 for studying and collecting plant genetic resources. In this year the activities have been concentrated on Sicily. 225 samples, mainly of vegetables, grain legumes and some cereals have been collected. A good part of the material is represented by highly variable old land-races; this is especially true for oats, barley, maize, french beans, faba beans,Brassica spp. and many other vegetables. Whereas genetic erosion is rather advanced in cereals, especially in wheat, land-races of many species of vegetables are grown on a large scale. The results of this mission increase our knowledge concerning the flora of cultivated plants of South Italy considerably. In Fortführung von Sammelreisen der letzten fünf Jahre wurde im September/Oktober 1985 eine weitere Reise nach Süditalien gemeinsam von Mitarbeitern des Istituto del Germoplasma, Bari, und des Zentralinistituts für Genetik und Kulturpflanzenforschung, Gatersleben, unternommen, die dem Studium und der Sammlung pflanzlicher genetischer Ressourcen diente. In diesem Jahr konzentrierten sich die Aktivitäten auf Sizilien. 225 Proben, besonders von Gemüsen, Körnerleguminosen und einigen Getrieiden wurden gesammelt. Ein beachtlicher Teil des Materials besteht aus hochvariablen alten Landsorten, besonders von Hafer, Gerste, Mais, Gartenbohnen, Ackerbohnen,Brassica-Arten und vielen anderen Gemüsen. Während die Generosion bei den Getreiden und besonders beim Weizen schon weit fortgeschritten ist, werden Gemüselandsorten noch in großem Umfang angebaut. Die Ergebnisse dieser Sammelreise erweitern unsere Kenntnisse zur Kulturpflanzenflora Süditaliens beträchtlich. Как продолжение экспедиций по сбору, проводимых в последние пять лет, в сентябре — октябре 1985 года сотрудниками Центрального института генетики и исследования культурных растений (Гатерслебен) и Института зародышевой плазмы (Бари) была предпринята последующая совместная экспедиция по изучению и сбору растительных генетических ресурсов в южной Италии. В этом году работы проводились в Сицилии. Было собрано 225 образцов, главным образом овощей, зернобобовых и некоторых злаковых. Значительная часть материала состоит из весьма изменчивых старых, местных сортов, в частности овса, ячменя, кукурузы, фасоли обыкновенной, конских бобов, видовBrassica и многих других овощей. В то время, как эрозия генов значительно развилась у злаковых, особенно у пшениц, местные сорта овощей продолжают возделываться в большом объёме.

The dynamics of plant bioresources including agriculture is different in the hills from those in the plains. The agriculture and forestry are the two major land use types and play an important role in providing food and livelihood security. The structure of vegetation for trees and shrubs layer was moderately instable and uneven as few species such as Acacia catechu, Lantana camara, Carissa spinarium in Mandhala; Quercus leucotrichophora, Pinus roxburghii, Myrsine africana in Moolbari, and Salix denticulata, Pinus wallichiana and Picea smithiana in Megad dominated the vegetation. Species richness was high at lower altitudes and low as we go higher. The distribution of species was mainly contiguous, however, few species showed random and regular distribution. Agricultural patterns have changed from traditional and subsistence to modern, which are primarily monoculture of high-valued cash crops. This has enhanced farm incomes but at the same time led to severe genetic erosion of tradi...

Jackfruit ( Artocarpus heterophyllus Lam.) Diversity in Bangladesh: Land Use and Artificial Selection. Bangladesh is often recognized as a secondary center of diversity for jackfruit (Artocarpus heterophyllus Lam.) and is expected to harbor important genetic diversity of this underutilized tree crop. Unfortunately, genetic erosion is occurring before this rich local resource has been documented and utilized for potential crop improvement. The aim of this study was to carry out a village-based survey and make morphological measurements to document and assess jackfruit diversity across trees associated with a gradient of three locations/habitats (homesteads, public lands, and forest or fallow lands). We also tested the hypotheses that cultivated jackfruit found in homesteads exhibited positive selection pressure for characteristics desirable in the market, and that the tree location reflected its history of origin and human selection. This was accomplished using 28 standardized morpho...

In several regions of Italy as well as other parts of southern Europe, the heterogeneity of the land, the climate and the soil favour the survival in cultivation of a large number of landraces specifically adapted to local conditions. Knowledge on the level and distribution of their genetic variation can help to develop appropriate strategies, in order to suistainably manage in situ these germplasm resources at risk of genetic erosion. C. annuum is an herbaceous diploid species and is considered to be self-pollinating, although different rates of out-crossing have been recorded. We used random amplified polymorphic DNA (RAPD) and amplified fragment length polymorphism (AFLP) markers to assess genetic diversity within and between five populations of a landrace of Capsicum annuum L., grown in a limited area in north-west Italy and locally known as ‘Cuneo’ pepper. Partitioning the genetic variation with Shannon's diversity index revealed that 41.6% occurred between and 58.4% within populations. Analogous results were obtained when the analysis was based only on RAPD or AFLP markers. However, AFLP was more reliable, since a lower range of variation was observed among primer combinations in detecting the two components of genetic variation. Notwithstanding the rather high level of within genetic variation detected, the five populations were clearly differentiated and differed in the frequency of alleles exclusive and/or present at very low frequencies. Our results show the need for accurate estimation of allele frequencies, in order to identify populations to which priority should be given for dynamic conservation of landraces.

Several legume crops like cowpea (Vigna unguiculata Walp.) and lablab (Lablab purpureus (L.) Sweet) originated from Africa. Nevertheless, the production of lablab is impaired by the successful establishment of common bean (Phaseolus vulgaris) in African agriculture most likely resulting in genetic erosion of the former. On the other hand, cowpea, particularly the cultivar group unguiculata, has long been cultivated in

This study reports on the analysis of 21 local melon cultivars (Cucumis melo L.) collected in the South of Tunisia which were compared to three modern melon cultivars widely-grown in this area. The analysis was based on the morphological characterization of fruits. Modern cultivars were significantly different from local germplasm as they were more firm and had higher sugar content.