Showing papers in "Aspects of applied biology in 2009"

Determination of aphid transmission efficiencies for N, NTN and Wilga strains of Potato virus Y

Abstract: Potato virus Y (PVY, genus Potyvirus, family Potyviridae) causes high economic losses worldwide, especially in the production of seed potatoes (Solanum tuberosum). PVY control systems rely on measuring virus pressure and vector pressure in the field. Calculation of the vector pressure is based on the relative efficiency factors (REFs) of aphid species. These REFs express the transmission efficiency of aphid species in relation to the transmission efficiency of Myzus persicae, the most efficient vector of PVY. In this paper, we report on the determination of aphids' relative transmission efficiency factors (REFs) for isolates of the PVY strains PVYN, PVYNTN and PVYN-Wi. Biotype Mp2 of M. persicae was tested for its transmission efficiency for six PVY isolates (one PVYN, three PVYNTN and two PVYN-Wi isolates) and showed comparable average transmission efficiencies for all isolates. The transmission rate of this biotype for the six PVY isolates was set to 1 and Mp2 was used as an internal control in transmission experiments to determine the REFs of three other biotypes of M. persicae and 16 other aphid species (three biotypes per species when available) for the six PVY isolates. Comparing the calculated REFs for PVYN with the REFs reported in the previous century for PVYN, we observe overall comparable REFs, except for Aphis fabae, Aphis spp., Hyperomyzus lactucae, Macrosiphum euphorbiae and Rhopalosiphum padi, which have a lower REF in our experiments, and Aphis frangulae and Phorodon humuli, which have now a higher REF. Comparing the new REFs found for the PVYNTN strains with the new REFs for PVYN, we observe that they are overall comparable, except for A. frangulae (0.17 compared with 0.53) and Schizaphis graminum (0.05 compared with 0.00). Comparing the REFs calculated for PVYN-Wi with those calculated for PVYN, we can observe six aphid species with higher REFs (Acyrthosiphon pisum, A. fabae, Aphis nasturtii, Aphis spp., P. humuli and R. padi). Only the species A. frangulae shows a lower REF for PVYN-Wi compared with the transmission efficiency of PVYN. Three aphid species (Aulacorthum solani, Myzus ascalonicus and S. graminum) for which no REF was determined earlier were found to be capable to transmit PVY and their REFs were determine

Learning about positive plant-microbial interactions from the System of Rice Intensification (SRI).

Abstract: 1Cornell International Institute for Food, Agriculture and Development, Ithaca, NY 14853, USA 2Director of Soil Biotechnology Laboratory, Bogor Agricultural University, Darmaga Campus, Bogor, Indonesia 3Former Principal Scientist, ICRISAT, Patancheru 502 324, India 4Directorate of Water Management, Bhubaneswar 751 023, India 5Former Director, Centre for Crop and Soil Management Studies, Tamil Nadu Agricultural University, Coimbatore 641 003, India

Investigating climate change impacts and adaptation options using integrated assessment methods

Abstract: Summary This paper illustrates the need for a range of methods, operating at different levels of representation and complexity, in order to investigate the impacts of climate change on agriculture and the subsequent development of appropriate adaptation strategies. Three examples are given: 1. agro-meteorological metrics developed through a social co-learning process with stakeholders (simple but easier to communicate); 2. estimates for a spring barley crop using a generic cropping systems model (medium complexity); 3. estimates of grass production under a sheep grazing regime using the same crop model (higher complexity). The metrics and estimates are derived from observed weather data and downscaled future projection data from the HadRM3 Regional Climate Model. Results are shown to illustrate the complementarities between methods and how their combination creates a clearer picture of what conditions may be like in the future. The three levels indicate the need for a step-wise process for engagement with stakeholders.

Assessing the environmental impacts of contrasting farming systems.

Abstract: Summary This paper examines how opportunity costs of land use can be taken into account when life cycle assessment (LCA) is used to compare environmental impacts of contrasting farming systems. Energy and greenhouse gas (GHG) balances of organic, conventional and integrated farm models are assessed. It is assumed that the farm size and food product output are equivalent in all farm models, and the remaining land that is not needed for food crops is used for Miscanthus energy crop production. The impacts of integrating biogas production into the farming systems are also explored. The results illustrate the significance of taking into account the opportunity costs of land use and suggest that integrated farming systems have potential to reduce negative environmental impacts compared to organic and conventional systems.

Applications of high-throughput techniques to the understudied crops of Africa.

Abstract: Summary Understudied, underutilized- or orphan- crops provide income for subsistence farmers and staple food for low income consumers in Africa. The major bottlenecks in productivity of these crops are low yield, finger millet (Elellsine coracana) and tef (Eragrostis tef), poor in nutrition, cassava (Manihot esculenta) and enset (Ensete ventricosum), and toxicity, cassava and grass pea (Lathyrus sativus). Drought, soil acidity and salinity, pests, diseases and weeds contribute to losses in yield. An agricultural revolution is needed to increase food production in Africa. The reverse genetics approach called TILLING (Targeting Induced Local Lesions IN Genomes) can be applied to the understudied crops ofAfrica. TILLING, a high-throughput and low cost method for the discovery ofinduced mutations, is currently applied to several crop species. TILLING has been modified as ecoTILLING to identify natural nucleotide polymorphisms. We describe two projects on TILLING and ecoTILLING aimed at finding the limiting factor in tef production.

Contribution of integrated farm management (IFM) to Defra objectives.

Abstract: Summary A farming system comprises a complex of interrelated and interacting factors. Any study of an isolated part of the system will not provide adequate understanding of the behaviour of the entire system and interactions may be equally or more important than individual components. There is therefore a requirement for the development of integrated approaches and practices to help farming systems adapt to, eliminate or reduce the negative impacts of production on the environment. This must be achieved whilst maintaining the economic viability of the farm enterprise. Our analysis has confirmed that IFM techniques generally have far more beneficial than adverse effects on current Defra policy objectives. However, there are some notable ‘conflicts’ where a technique that has a large beneficial effect in one policy area has a large negative effect in another. Carbon footprinting is used to quantify the impact of some integrated farming practices.

Cowpea landraces of Botswana: a potential resistance source for Alectra vogelii.

Abstract: Cowpea (Vigna unguiculata [L] Walp.) is primarily grown in drier regions of the world where it is one of the most drought resistant food legumes. The southernmost region of Africa is most probably the center of origin where many wild relatives of the species are found in abundance. Botswana is one of the Southern African countries that has the highest genetic diversity in respect of wild forms of cowpea. In Botswana, cowpea is widely grown and plays an important role in the economy and diet of both the rural and urban population. However, cowpea yield is negatively affected by different biotic and abiotic factors. Witchweed (Alectra vogelii), an obligate root parasite, is one of the major constraints to cowpea production in sub-Saharan Africa including Botswana. Up to 100% yield losses of susceptible varieties have been observed in some farmers' fields. Control of Alectra is difficult because of its enormous seed reserve in the soil that can germinate and cause significant damage to susceptible cultivars even before the weed emerges above the ground. Earlier studies indicate that B359, a landrace from Botswana, is a source of resistance to the parasite and is being used in the breeding program. However, this genotype produces only a few flowers per plant and there is an insufficient amount of pollen for crossing. This study was conducted to identify additional or alternative sources of resistance from both cultivated and wild cowpeas collected from Botswana for developing Alectra resistant varieties which is perhaps the most feasible means of reducing crop losses caused by Alectra attack. A total of 66 cultivated and 20 wild cowpeas were tested under high Alectra pressure in a greenhouse at Sebele Agricultural Research Station, Botswana, during 2008. Twelve of the cultivated genotypes, namely B426A, B415, B413, B403, B400, B336, B399, B432, B416, B397, B404, and B359 showed resistance to Alectra infection. Furthermore, 14 of the wild cowpeas did not show any sign of infection. The majority of cultivated cultivars had thicker stems at above the soil level and interestingly this morphological character showed negative correlations with Alectra infection. Such cultivars showed puffy stems at early seedling stage. Generally there was lower incidence of Alectra infection among cowpea genotypes with thicker stems which could be used as a selection criterion if confirmed. Genotypes identified for resistance to the parasite will be further evaluated under different growing conditions.

A comparison of two models to predict nitrogen dynamics in organic agricultural systems

Abstract: Two publicly available crop/soil models were compared. These were the EU-Rotate_N model (www.warwick.ac.uk/go/eurotaten) and the NDICEA model (www.ndicea.nl). Each simulation was also compared to measured data from an organically managed site in the English Midlands. Results showed that, overall, EU-Rotate_N gave a better estimation of soil mineral nitrogen, particularly after the incorporation of a long-term fertility-building crop. This model has a lot of flexibility but is aimed at researchers and requires more work before it is ready to be used by farmers or advisors. The NDICEA model is much simpler to use with a user-friendly interface.

Integration across disciplines: the lessons learnt from the integrated project SEAMLESS.

Abstract: This contribution presents a methodology for integrated assessment of agricultural systems, illustrates its application and discusses its flexibility and limitations. It also reflects on how the methodology was developed in a large European and interdisciplinary research project (SEAMLESS) and how it will be maintained and further extended. The methodology consists of components simulating well defined processes at specific scales, that can be used stand-alone, but that can also be linked through a software infrastructure to address the multi-scale and highly integrated problems that agriculture is facing. The component-based structure allows it to benefit from the work of related disciplinary teams (agro-ecologists, farming systems researchers, agricultural economists, etc.) for integrative purposes. The conceptual and technical linking of the components includes methods for up and downscaling and ontology development ensuring consistent exchanges of inputs and outputs across components. This integrative work is highly interdisciplinary and requires a generation of scientists with sufficient multidisciplinary knowledge, familiarity with novel IT concepts and high motivation to integrate knowledge across domains and scales. The resulting integrated framework has been tested and applied to a broad range of farm types and agricultural systems across the EU, including arable and livestock farming, to assess agricultural, environmental and trade policies at European, regional and local level.