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Annicchiarico P.,Italian Agricultural Research Council | Pecetti L.,Italian Agricultural Research Council | Abdelguerfi A.,Montpellier SupAgro | Bouizgaren A.,French National Institute for Agricultural Research | And 4 more authors.
Field Crops Research | Year: 2011

Lucerne (Medicago sativa L.) can enhance the economic and environmental sustainability of crop-livestock systems in the western Mediterranean basin, but requires improved adaptation to stressful environments because of a predicted shortage of irrigation water and climate change. This study reports on three-year dry matter yields of five landraces from Morocco, Italy and Tunisia and seven varieties from France, Italy, Australia and USA assessed across 10 agricultural environments of Algeria, Tunisia, Morocco and Italy of which four were rainfed, one was continuously irrigated (oasis management), and five were irrigated but adopted a nine-week suspension of irrigation during summer. Our objectives were targeting cultivars to specific environments, and assisting regional breeding programmes in defining adaptation strategies, genetic resources and opportunities for international co-operation. The crop persisted well in all environments, but environment mean yield was strictly associated (P<0.01) with annual and spring-summer (April-September) water available. Rainfed cropping implied 42% lower yield with 61% less spring-summer water available relative to irrigation with withheld summer water across three sites hosting both managements. All of these sites showed genotype×management interaction (at least P<0.10). Cross-over genotype×environment (GE) interaction between top-yielding cultivars occurred across the 10 environments. Total number of harvests (range: 9-23), soil salinity as measured by electrical conductivity (range: 0.20-6.0dSm-1), and average spring-summer water available (range: 102-932mm) were selected as significant (P<0.05) environmental covariates in a factorial regression model explaining 53% of GE interaction variation. This model was exploited for targeting cultivars as a function of site-specific levels of these factors. Its indications agreed largely with those of an additive main effects and multiplicative interaction model with two GE interaction principal components. An Italian landrace exhibited specific adaptation to severely drought-prone environments, whereas landraces from north Africa were not adapted to such environments. One Moroccan landrace was specifically adapted to high number of harvests (partly reflecting frequent mowing). One variety selected for salt tolerance, and one Moroccan landrace, were specifically adapted to salt-stress environments. Environment classification as a function of GE interaction effects indicated three groups which may be object of specific breeding: (i) rainfed or irrigated environments featuring limited spring-summer water available (<350mm), nil or low soil salinity, and moderate to low number of harvests; (ii) salt-stress environments; and (iii) environments characterized by high number of harvests. © 2010 Elsevier B.V. Source

Gamoun M.,Institute des Regions Arides IRA | Patton B.,North Dakota State University | Hanchi B.,University of Tunis
International Journal of Biodiversity Science, Ecosystems Services and Management | Year: 2015

Livestock grazing influences arid rangelands greatly with important effects on vegetation dynamics. Two areas traditionally grazed by sheep and goats in southern Tunisia were sampled to evaluate the vegetation response to grazing management. A continuous grazing (CG) area was sampled in March 2007. A 2000 ha exclosure that had been rested for 3 years (2004-2007), grazed for 2 months (July and August 2007), and then rested for 7 months (September 2007 to February 2008) was sampled before and after grazing, and again after the 7 months' rest. Results show that vegetation dynamics in arid rangelands respond strongly to changes in grazing management. Our results suggest that even previously overgrazed rangelands are resilient and are able to recover if given rest periods. In the studied Tunisian rangeland that has been moderately or lightly grazed, we found that recovery improved faster compared with continuously grazed. In practice, excluding grazing livestock and the use of a rotational grazing system are available ways to restore vegetation affected by CG. Therefore, a stocking rate not exceeding the carrying capacity is vital to maintain grazing operations under changing conditions and sustain rangeland resources over the long term. Increased stocking rates generally promote rangeland degradation © 2015 Taylor & Francis. Source

de Graaff J.,Wageningen University | Aklilu A.,Addis Ababa Institute of Technology | Ouessar M.,Institute des Regions Arides IRA | Asins-Velis S.,University of Valencia | Kessler A.,Wageningen University
Land Use Policy | Year: 2013

Since the 1930s there has been worldwide concern about the effects and impacts of land degradation. After the problems experienced in the Dust Bowl in the USA, much attention was paid to soil and water conservation in both developed and developing countries. Initially Governments stimulated the establishment of physical control measures, such as terraces, check dams and reforestation. This was achieved through top-down regulations, and Forestry Departments were often in charge of the implementation. Subsequently the measures were implemented through more specialized agencies, and later with incentives, such as food aid in developing countries and subsidies in developed countries. In some cases farmers were mobilized to work together on the establishment of the conservation measures. Because of the low success rate of this top-down approach with line interventions, it was realized that a more participatory approach had to be followed. The emphasis then shifted to area interventions such as cover crops, mulching and composting. In some countries voluntary ways of collaboration between farmers were developed. More recently Conservation Agriculture has become popular, focusing on less soil disturbance, continuous land cover and crop rotations. This paper analyses whether and to what extent countries have followed such general trends in their soil and water conservation policies (since the 1990s often referred to as sustainable land management) or whether countries have also followed their own specific strategies. A historical (1960-2010) and comparative analysis of the development of these sustainable land management policies and practices is undertaken in five selected countries: Indonesia, Ethiopia, Tunisia, Spain and Bolivia. © 2012 Elsevier Ltd. Source

The response of a plant community to protection from grazing, as a function of year and soil type, was studied in the arid rangelands of southern Tunisia between 2007 and 2009. The vegetation of rangelands is often altered under grazing pressure, but unfortunately, removing the grazing pressure often does not reverse the changes in the way the succession model predicts. Rainfall variability is a key driver of ecosystem structure and function in arid rangelands, and this arid area of North Africa is characterized by low and erratic rainfall and is prone to drought conditions which normally occur every two to three years. Steppes are likely to exhibit strong and rapid structural and functional responses to these altered rainfall patterns. Although drought affects vegetation cover more in loamy soil than in all other soils, it affects diversity on all soils; particularly limestone and loam soils. Source

Jeridi M.,CIRAD - Agricultural Research for Development | Jeridi M.,Institute des Regions Arides IRA | Bakry F.,CIRAD - Agricultural Research for Development | Escoute J.,CIRAD - Agricultural Research for Development | And 5 more authors.
Annals of Botany | Year: 2011

Background and AimsMost cooking banana and several desert bananas are interspecific triploid hybrids between Musa acuminata (A genome) and Musa balbisiana (B genome). In addition, M. balbisiana has agronomical characteristics such as resistance to biotic and abiotic stresses that could be useful to improve monospecific acuminata cultivars. To develop efficient breeding strategies for improving Musa cultivars, it is therefore important to understand the possibility of chromosome exchange between these two species.MethodsA protocol was developed to prepare chromosome at meiosis metaphase I suitable for genomic in situ hybridization. A series of technical challenges were encountered, the main ones being the hardness of the cell wall and the density of the microsporocytes cytoplasm, which hampers accessibility of the probes to the chromosomes. Key parameters in solving these problems were addition of macerozyme in the enzyme mix, the duration of digestion and temperature during the spreading phase.Results and ConclusionsThis method was applied to analyse chromosome pairing in metaphase from triploid interspecific cultivars, and it was clearly demonstrated that interspecific recombinations between M. acuminata and M. balbisiana chromosomes do occur and may be frequent in triploid hybrids. These results provide new insight into Musa cultivar evolution and have important implications for breeding. © The Author 2011. Source

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