Lopez-Escudero F.J.,University of Cordoba, Spain |
Mercado-Blanco J.,CSIC - Institute for Sustainable Agriculture
Plant and Soil | Year: 2011
Olive (Olea europaea L.) is one of the first domesticated and cultivated tree species and has historical, social and economical relevance. However, its future as a strategic commodity in Mediterranean agriculture is threatened by diverse biotic (traditional and new/emerging pests and diseases) and abiotic (erosion, climate change) menaces. These problems could also be of relevance for new geographical areas where olive cultivation is not traditional but is increasingly spreading (i. e., South America, Australia, etc). One of the major constraints for olive cultivation is Verticillium wilt, a vascular disease caused by the soil-borne fungus Verticillium dahliae Kleb. In this review we describe how Verticillium wilt of olive (VWO) has become a major problem for olive cultivation during the last two decades. Similar to other vascular diseases, VWO is difficult to manage and single control measure are mostly ineffective. Therefore, an integrated disease management strategy that fits modern sustainable agriculture criteria must be implemented. Multidisciplinary research efforts and advances to understand this pathosystem and to develop appropriate control measures are summarized. The main conclusion is that a holistic approach is the best strategy to effectively control VWO, integrating biological, chemical, physical, and cultural approaches. © 2010 The Author(s).
Vaz Patto M.C.,New University of Lisbon |
Rubiales D.,CSIC - Institute for Sustainable Agriculture
Annals of Botany | Year: 2014
Background The Lathyrus genus includes 160 species, some of which have economic importance as food, fodder and ornamental crops (mainly L. sativus, L. cicera and L. odoratus, respectively) and are cultivated in >1·5 Mha worldwide. However, in spite of their well-recognized robustness and potential as a source of calories and protein for populations in drought-prone and marginal areas, cultivation is in decline and there is a high risk of genetic erosion. Scope In this review, current and past taxonomic treatments of the Lathyrus genus are assessed and its current status is examined together with future prospects for germplasm conservation, characterization and utilization. A particular emphasis is placed on the importance of diversity analysis for breeding of L. sativus and L. cicera. Conclusions Efforts for improvement of L. sativus and L. cicera should concentrate on the development of publicly available joint core collections, and on high-resolution genotyping. This will be critical for permitting decentralized phenotyping. Such a co-ordinated international effort should result in more efficient and faster breeding approaches, which are particularly needed for these neglected, underutilized Lathyrus species. © 2014 The Author.
Garcia-Moreno M.J.,CSIC - Institute for Sustainable Agriculture
BMC plant biology | Year: 2012
Tocopherols are natural antioxidants with both in vivo (vitamin E) and in vitro activity. Sunflower seeds contain predominantly alpha-tocopherol (>90% of total tocopherols), with maximum vitamin E effect but lower in vitro antioxidant action than other tocopherol forms such as gamma-tocopherol. Sunflower germplasm with stable high levels of gamma-tocopherol (>85%) has been developed. The trait is controlled by recessive alleles at a single locus Tph2 underlying a gamma-tocopherol methyltransferase (gamma-TMT). Additionally, unstable expression of increased gamma-tocopherol content in the range from 5 to 85% has been reported. The objective of this research was to determine the genetic basis of unstable expression of high gamma-tocopherol content in sunflower seeds. Male sterile plants of nuclear male sterile line nmsT2100, with stable high gamma-tocopherol content, were crossed with plants of line IAST-1, with stable high gamma-tocopherol content but derived from a population that exhibited unstable expression of the trait. F2 seeds showed continuous segregation for gamma-tocopherol content from 1.0 to 99.7%. Gamma-tocopherol content in F2 plants (average of 24 individual F3 seeds) segregated from 59.4 to 99.4%. A genetic linkage map comprising 17 linkage groups (LGs) was constructed from this population using 109 SSR and 20 INDEL marker loci, including INDEL markers for tocopherol biosynthesis genes. QTL analysis revealed a major QTL on LG 8 that corresponded to the gamma-TMT Tph2 locus, which suggested that high gamma-tocopherol lines nmsT2100 and IAST-1 possess different alleles at this locus. Modifying genes were identified at LGs 1, 9, 14 and 16, corresponding in most cases with gamma-TMT duplicated loci. Unstable expression of high gamma-tocopherol content is produced by the effect of modifying genes on tph2a allele at the gamma-TMT Tph2 gene. This allele is present in line IAST-1 and is different to allele tph2 present in line nmsT2100, which is not affected by modifying genes. No sequence differences at the gamma-TMT gene were found associated to allelic unstability. Our results suggested that modifying genes are mostly epistatically interacting gamma-TMT duplicated loci.
Rubiales D.,CSIC - Institute for Sustainable Agriculture |
Monica F.-A.,Virginia Polytechnic Institute and State University
Agronomy for Sustainable Development | Year: 2012
Parasitic weeds decrease severely the production of major grain and forage legumes. The most economically damaging weeds for temperate legumes are broomrapes, in particular Orobanche crenata. Broomrape species such as Orobanche foetida, Orobanche minor, and Phelipanche aegyptiaca can also induce high local damage. Other parasitic weeds such as Striga gesnerioides and Alectra vogelii decrease yield of legume crops throughout semi-arid areas of sub-Saharan Africa. Dodders such as Cuscuta campestris can be damaging for some crops. Here, we review methods to control parasitic weeds. Preventing the movement of weed seeds into uninfested areas is a crucial component of control. Once a field is infested with parasitic weeds, controlling its seed production is very difficult. The only effective way to cope with parasitic weeds is to apply an integrated approach. Seedbank demise can be achieved by fumigation and solarization. However, this method is not economically feasible for low-value and low-input legume crops. A number of cultural practices including delayed sowing, hand weeding, no-tillage, nitrogen fertilization, intercropping, or rotations can contribute to seed bank demise. Other strategies such as suicidal germination, activation of systemic acquired resistance, biocontrol or target site herbicide resistance are promising solutions that are being explored but are not yet ready for direct application. The only methods currently available to farmers are the use of resistant varieties and chemical control, although both have their limitations. Chemical control with systemic herbicides such as glyphosate or imidazolinones at low rates is possible. Advances in modeling and the availability of new technologies allow the development of precision agriculture or sitespecific farming. The most economical and environmentally friendly control option is the use of resistant crop varieties; however, breeding for resistance is a difficult task considering the scarce and complex nature of resistance in most crops. These strategies for parasitic weed management in legume crops will be presented and critically discussed. © INRA and Springer Science+Business Media B.V. 2011.
Lopez-Granados F.,CSIC - Institute for Sustainable Agriculture
Weed Research | Year: 2011
This work describes the current status of remote and proximal (on-ground) weed detection systems for site-specific weed management and discusses the limitations and opportunities of these technologies. Remote sensing based on multispectral aerial imagery can provide accurate weed maps, especially at late weed phenological stages, whereas images from high spatial resolution satellite and unmanned aerial vehicles must still be analysed. Hyperspectral images produce highly accurate maps at early and late phenological stages at a farm scale or medium spatial scale. However, this technology is not profitable, because of current operating costs, which are prohibitive. In studies of on-ground weed seedling detection, accurate results can be obtained at a medium farm scale. Despite numerous efforts, a powerful and flexible classifier of soil, weeds and crops in a number of situations, remains the greatest challenge of this technology. The main limitations of remote and proximal sensing may be summarised in the following two points: (i) the time and education required for applying new technological advances and (ii) the high cost of the technology and the lack of compatibility of the machinery. Possible solutions might include: (i) offering an advisory service that provides technical support, agronomic knowledge and specific training courses, (ii) the development and implementation of uniform and cheaper standards, (iii) increased research of both high resolution satellite imagery exploring object-based image analysis and pan-sharpened imagery and unmanned aerial vehicles (UAV) and (iv) enabling the development of current prototypes of robotic weeding into commercial products. The general lack of multidisciplinary research groups can be a disadvantage when comparing the economic feasibility of site-specific weed management with conventional systems. © 2010 CSIC. Weed Research © 2010 European Weed Research Society.
Castro-Orgaz O.,CSIC - Institute for Sustainable Agriculture
Journal of Hydraulic Research | Year: 2010
The common treatment of open channel flow involves the hydrostatic pressure approach. However, many flows are curvilinear and a higher-order approach is needed to deal with the non-hydrostatic pressure distribution. The current models are based on linear relationships for the variation of streamline curvature and inclination along the equipotential curves of the flow net, yet this approach is not verified with 2D results. In the present study typical 2D free surface flow nets are analysed to investigate the variations of streamline curvature and inclination. From the detailed 2D information, approximate relationships describing the curvature and inclination are proposed. It was found that streamline curvature and inclination do not vary linearly in general. The higher-order energy and momentum curvilinear equations are improved with this approach, thereby approximating the real flow net geometry. The implications of these findings on curvilinear flow modelling are discussed using several test cases. © 2010 International Association for Hydro-Environment Engineering and Research.
Castro-Orgaz O.,CSIC - Institute for Sustainable Agriculture
Journal of Hydraulic Research | Year: 2010
The undular hydraulic jump is a transitional flow phenomenon where both streamline curvature and frictional effects are important. In the past, streamline curvature effects were treated with the Boussinesq equations for the potential flow approach, thereby overlooking the real flow features. If friction is included, additional terms appear, because the specific energy variation along the undular jump is related to the boundary shear stress. However, these effects are neither addressed in the literature, nor compared with the classical Boussinesq-type solutions. Also, neither information on how boundary layer methods for adverse pressure gradients behave in undular flows is available, nor experimental data. Herein the frictional effects on the Boussinesq equations are systematically analysed using boundary layer methods for adverse pressure gradients. Based on these results, a new simplified approach is proposed to reasonably reproduce the oscillatory boundary layer characteristics in weakly undular hydraulic jumps under a steadily changing pressure gradient from adverse to favourable, and vice versa. © 2010 International Association for Hydro-Environment Engineering and Research.
Castro-Orgaz O.,CSIC - Institute for Sustainable Agriculture
Journal of Irrigation and Drainage Engineering | Year: 2013
Weirs used for water discharge measurement in open-channel systems normally operate under free-flow conditions, for which the specific energy reaches a minimum at the weir crest. This type of transitional open-channel flow can be simulated using the ideal fluid flow theory. The traditional application of that theory requires the computation of the flow net over the weir. In this work, a potential flow model using a semi-inverse mapping is proposed in order to simulate potential flow over weirs. The model reduces the computation of the entire flow net to the determination of the streamlineflow pattern only. The computations are conducted numerically using a simple finite-difference technique, in which conservation of energy, momentum, and the critical flow condition with curvilinear streamlines is considered. The model is used to display parameters of engineering interest at the point of minimum specific energy. © 2013 American Society of Civil Engineers.
Brouder S.M.,Purdue University |
Gomez-Macpherson H.,CSIC - Institute for Sustainable Agriculture
Agriculture, Ecosystems and Environment | Year: 2014
Widespread implementation of conservation agriculture (CA) in North and South America and Australia suggests significant farmer profitability achieved through some combination of sustained or increased agronomic productivity and reduced input costs. Many believe similar agronomic benefits can accrue to smallholder farmers in sub-Saharan Africa (SSA) and South Asia (SA) for a broad array of crops and farming systems despite marked differences in biophysical and socio-economic environments across these regions. Our objectives were to characterize (1) the quality of existing research including an assessment of the relevance of previously published reviews and surveys to SSA and SA, and (2) the empirical evidence from SSA and SA for agronomic benefits derived from implementing zero tillage (ZT) including the identification of knowledge gaps. Mulching and rotation were considered as associated practices within systems. Among surveys and reviews, most syntheses of multiple, independent studies were either entirely qualitative or used overly simplistic approaches to data aggregation. Few reviews used meta-analysis or other rigorous statistics that permit assessment of outcome sensitivity to influential observations; in general, review protocol descriptions were not sufficient to ensure transparency and appropriate handling of common biases. A search and screening of peer-reviewed literature identified empirical studies on conservation tillage in SSA and SA for maize (22), rice (16), cowpea (10) and sorghum (8). In attempting to extract data for an unbiased, systematic review of CA and maize, we found few studies fully reported critical data or meta-data; most common omissions were the univariate statistics required for study use in meta-analyses and critical supporting or explanatory data on soil type, prevailing weather, and management practices including handling of crop residues. In the short-term, ZT generally resulted in lower yields than with conventional tillage (CT). Occasionally these reductions could be linked to direct effects (e.g. increased soil compaction in rice), but failure to adapt other managements (e.g. weed control) to the CA system was a common and confounding indirect effect. Sufficient maize data existed to demonstrate that negative impacts on yield ameliorated with time in some cases accompanied by higher soil water infiltration and soil organic matter, particularly when mulch was added. However, the low number of studies, the missing supporting data and the large variation in treatments made it difficult to infer general direct effects due to mulching or rotation.Well-designed long-term experiments on CA featuring sound agronomic practice and comprehensive documentation are largely missing from the literature. Future systematic reviews addressing agronomic impacts of CA interventions will require appropriate handling of within and between study variance as well as sensitivity analyses and quantitative assessments of publication bias; on-going and future empirical studies must report a minimum dataset encompassing valid statistical measures and comprehensive intervention descriptions that enable standardization and systematic approaches in syntheses. We propose a minimum dataset that is generic to competent agronomy with measurements that are increasingly low-cost and easy to achieve and should therefore be routine in field experiments quantifying and explaining crop and cropping system performance. Until a larger number of field studies provide such quantifying and explanatory data from key crops and representative cropping systems, it is not possible to make strong general conclusions about benefits of CA and ZT on yields and resource use efficiency of smallholder farmers. © 2013 Elsevier B.V.
Zarco-Tejada P.J.,CSIC - Institute for Sustainable Agriculture |
Gonzalez-Dugo V.,CSIC - Institute for Sustainable Agriculture |
Berni J.A.J.,CSIC - Institute for Sustainable Agriculture
Remote Sensing of Environment | Year: 2012
The remote detection of water stress in a citrus orchard was investigated using leaf-level measurements of chlorophyll fluorescence and Photochemical Reflectance Index (PRI) data, seasonal time-series of crown temperature and PRI, and high-resolution airborne imagery. The work was conducted in an orchard where a regulated deficit irrigation (RDI) experiment generated a gradient in water stress levels. Stomatal conductance (Gs) and water potential (Ψ) were measured over the season on each treatment block. The airborne data consisted on thermal and hyperspectral imagery acquired at the time of maximum stress differences among treatments, prior to the re-watering phase, using a miniaturized thermal camera and a micro-hyperspectral imager on board an unmanned aerial vehicle (UAV). The hyperspectral imagery was acquired at 40cm resolution and 260 spectral bands in the 400-885nm spectral range at 6.4nm full width at half maximum (FWHM) spectral resolution and 1.85nm sampling interval, enabling the identification of pure crowns for extracting radiance and reflectance hyperspectral spectra from each tree. The FluorMOD model was used to investigate the retrieval of chlorophyll fluorescence by applying the Fraunhofer Line Depth (FLD) principle using three spectral bands (FLD3), which demonstrated that fluorescence retrieval was feasible with the configuration of the UAV micro-hyperspectral instrument flown over the orchard. Results demonstrated the link between seasonal PRI and crown temperature acquired from instrumented trees and field measurements of stomatal conductance and water potential. The sensitivity of PRI and Tc-Ta time-series to water stress levels demonstrated a time delay of PRI vs Tc-Ta during the recovery phase after re-watering started. At the time of the maximum stress difference among treatment blocks, the airborne imagery acquired from the UAV platform demonstrated that the crown temperature yielded the best coefficient of determination for Gs (r 2=0.78; p<0.05) and Ψ (r 2=0.34; p<0.001). Among the narrow-band indices calculated, the PRI 515 index (reference band=515nm) obtained better results than PRI 570, with r 2=0.59 (p<0.01) for Gs, and r 2=0.38 (p<0.001) for Ψ. The BGI1 index calculated from the blue (R 400) and green (R 550) bands resulted on the highest significance levels (p<0.001) for both Gs (r 2=0.62) and Ψ (r 2=0.49). Out of the structural indices assessed, RDVI, MTVI1 and TVI showed greater sensitivity for Gs (r 2=0.6; p<0.01) and Ψ (p<0.001) than NDVI. Chlorophyll fluorescence calculated from the micro-hyperspectral imagery with the FLD3 method tracked stress levels, obtaining r 2=0.67 (p<0.05) with stomatal conductance, and r 2=0.66 (p<0.001) with water potential. The work presented in this manuscript demonstrates the feasibility of thermal, narrow-band indices and fluorescence retrievals obtained from a micro-hyperspectral imager and a light-weight thermal camera on board small UAV platforms for stress detection in a heterogeneous tree canopy where very high resolution is required. © 2011 Elsevier Inc.