QTL ANALYSIS OF ROOT CHARACTERISTICS IN MAIZE GROWN IN HYDROPONICS AS RELATED TO FIELD PERFORMANCE UNDER DROUGHT CONDITIONS

¹ Dept. of Agronomy, University of Bologna, ITALY

² International Maize and Wheat Improvement Center (CIMMYT), D.F. MEXICO

Root characteristics greatly affect the agronomic performance of crops grown under conditions of limited water and nutrient availability. Under field conditions, it is difficult to properly investigate roots in a large number of plants. As an alternative to root studies conducted in the field, we are evaluating the feasibility of using hydroponics to investigate root traits in maize. We report the results of two QTL studies carried out with two populations. One population (220 RIL) obtained at CYMMIT was field tested in Mexico for 2 years under 3 water regimes. In a first experiment in hydroponics, root traits of the 8 RIL characterized by the lowest (L-RIL) or the highest (H-RIL) yield were evaluated at the 4-leaf stage. The H-RIL significantly outperformed the L-RIL group for primary root length, diameter and dry weight, root branching, and dry weight of the shoot. Subsequently, the analysis in hydroponics was extended to 120 randomly chosen RIL. QTL were identified for primary root length, diameter, branching, dry weight, and root-to-shoot dry weight ratio. In some cases, the support interval of a number of these QTLs overlapped with QTLs of agronomically important traits. The second population included 171 F3 (Lo964 x Lo1016) families which were tested for root traits in hydroponics and for the main agronomic traits in the field under 2 water regimes. QTL analysis for this population is underway. The QTL results obtained will be compared and critically analysed based on available mapping information (e.g. drought-induced genes, yield QTL, etc.) for maize.