Mineral micronutrient density in local cereals sampled from Bungoma, Maseno and Kibwezi areas

Abstract

Cereals constitute a food staple in the African bread (Ugali) form. Overdependence on maize as a predominant staple is partly blamed on the constricting indigenous cereal phyto-diversity. Strategies rekindling interest in their restoration remain few and disconnected. Thus, the objectives were to: (1) search for micronutrient density information among accessions of sorghum, finger millet, pearl millet and maize on the basis of ‘where-they-were-as they-were’ (free-call diversity); (2) determine micronutrient densities linked to eco-nutrametric variation for distinguishing differences among accessions. The accessions were collected in 2003/04 from the Bungoma-Maseno-Kibwezi (BMK) phyto-regions and subjected to Energy Dispersive X-ray Fluorescence (XRF) analysis. A nested design was used for sampling in which the cereal species were nested within sites and sites nested within phyto-regions. For each accession with its soil, a gamut of element concentrations was XRF-generated. The data were subjected to a Clustered Bar Graphing (CBG) test for identifying variation-picking element(s). By CBG test, a given element’s concentration data range was placed along the X-axis upon which species/accessions’ density categories along the Y-axis were graphed as series in rows giving way to density variation comparisons. Where no such density variations were visible, the element was disregarded as non-variation-picking. The CBG test revealed that all accessions were ‘imperfect’ in that none of them had the gamut elements (density as subject score) inall- top or in-all-low density, i.e. none of the accessions scored high ‘As’ or low ‘Cs’ in every elemental density case. This implied that a phenotypic characterization as a whole would have required describing an accession in as different (number of) ways as the number of the variation-picking elements included. A soil-to-plant mineral flow (elemental uptake-ability or EU) was further calculated as a single value [plant ppm]/[soil] x 100. In sorghum the EUs were as follows: 2.4% for Fe (in accession tC74), 211% for Zn (in tC65), 332% for Cu (in tC36) and 408% for K in (tC70). The CBG test among the cereal accessions is invaluable for distinguishing within and between accessions in respect of their single element uptake-ability. A single nutrametric value (NMV) or grade, on the other hand, appears useful in describing a nutrametric phenotypic variant as it bypasses the genotype-environment interaction dilemma. Its robustness is its ability to distinguish various phenotypic mineral micronutrient diversity grading and offers opportunities for mineral micronutrient mapping across phyto-regions.