Role of participants

 

The distribution of responsibilities and tasks between the contractors with regard to the main project objective is shown in the project structure.

The proposed project structure can be broken down to 5 research fields, Plant Physiology, Plant Molecular Biology, Plant Improvement, Plant-Soil Interaction, and Agronomy interacting with each other in order to contribute to the development of sustainable maize cropping systems on acid soils.



Plant Improvement

  The research institutions EMBRAPA, IRAD and INRA are actively involved in the selection and breeding of cultivars adapted to the prevailing acid soils of their regions. Due to the complexity of soil acidity and plant/environment interactions, breeding of cultivars has to be site specific. However, the identification and incorporation of genes essential for acid-soil resistance would make the development of otherwise well adapted and high yielding cultivars much more efficient. Therefore, genetic material between these partners will be exchanged extensively, a common and breeding approach and original genetic models will be adopted which will allow the assessment of the genetic progress being achieved. Field screening using a standarized experimental design will be performed at all locations including a set of selected cultivars from the different breeding programmes including CIMMYT, Cali.



Agronomy

  Long-term experiments have been established 3 years ago by the CORPOICA and IRAD. These experiments comprise 2 lime rates, 2 P rates, 3 organic manure rates and different maize cultivars (local non-improved, improved and acid soil-resistant, acid soil-sensitive). The experiments have to be continued in order to be able to assess the effect of management strategies on soil chemical, biological and physical characteristics suitable as sustainability indicators with strong involvement and support of CIRAD using the available expertise in soil characterization and root-growth assessment and modelling. The field experimental design will be adapted and additional satellite experiments will be established in order to take existing and emerging information into consideration. The experimental approach will allow to study both, the effect on soil properties of cultivars differing in acid-soil resistance and the comparative advantage of the use of acid soil-resistant cultivars versus agronomic practices such as fertilizer application and organic matter management.



Physiology

  The physiological activities will concentrate on mainly two aspects which appear to be of primary importance for the understanding of Al toxicity and Al resistance and P efficiency according to previous work of the partners involved:

  1. synthesis, compartmentalisation and exudation of organic acids (UAB and EMRAPA) and
  2. Al-binding characteristics of the root apoplast mainly determined by the pectin matrix and the plasma membrane (UHANN). In these studies special attention will be paid to the spatial aspects within the root apex. All partners will closely collaborate with the Mol. Biol. groups (CSIC, CIEA, EMBRAPA, UEC) by characterising action and effects of genes, gene promoters, and gene products expected to be involved in the expression of Al resistance and P efficiency using transgenics.



Plant Molecular Biology

  The Plant Mol. Biol. groups will work on different levels:

  1. identification and characterisation of genes induced by Al in the root apex and by P deficiency expected to be involved in the expression and in sustaining Al resistance and P efficiency (EMBRAPA, UEC),
  2. the modification of the expression of genes controlling physiological processes such as citrate synthesis (CIEA), characteristics of the pectin matrix and the plasma membrane (UEC), identified as important in Al resistance and P efficiency,
  3. the analysis and characterization of root tissue-specific gene promoters which appears to be of uppermost importance in view of the spatial sensitivity and expression of Al resistance in the root apex and the peripheral cell layers (CSIC, UEC), and
  4. the identification of molecular markers for Al resistance and P efficiency and their evaluation in assisting the breeding for adaptation to soil acidity (EMBRAPA).



Plant-Soil Interaction

  This research field represents the bridge primarily between Plant Physiology and Agronomy. Fitting maize to acid soils requires a better quantitative understanding of the processes at the plant root/soil interface which is the rhizosphere. These processes are not only determined by plant characteristics, which will be modified by the breeders, the extent to which these plant characteristics will successfully contribute to improved acid soil tolerance depends on soil properties which can be modified by agronomic management practices. CIRAD will extend and further develop a model describing the dynamics of P and Al in the maize rhizophere taking physiological data of root responses to acid soil conditions and soil characteristics prevailing at the field experimental sites of CORPOICA and IRAD into account. The role of mycorrhiza in P efficiency and Al resistance will be studied by CORPOICA and considered trough a particularly close cooperation.