Time filter

Source Type

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. Source

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). Source

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. Source

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. Source

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. Source

Discover hidden collaborations