An Architectural Approach to Investigate Maize Response to Low Temperature

In maize, grain yield is highly associated with light interception and photosynthetic activity during grain filling. In Europe, this period typically occurs when solar radiation is already decreasing and water availability may be limiting. The improvement of cold-tolerance is a major challenge for maize production because earlier sowing would allow a better fit between crop cycle and availability of natural resources. Low temperatures have a major impact on (i) radiation interception through the modification of foliage development and (ii) radiation use efficiency (RUE) through the reduction of leaf photosynthetic activity. Little is known about the specific contribution of each of these traits to the lower biomass production under cold conditions and their genetic variability. A field experiment with two planting dates was carried out on four maize inbred lines from temperate or highland-tropical origin, chosen as source of genotypic and phenotypic variability for cold tolerance. Biomass production was measured over time and analysed with respect to the amount of radiative energy received by the plant to quantify the radiation use efficiency of the different genotypes. The major impact of early sowing was found through the reduction in leaf dimensions. Early sowing affected leaves growing both during and after the cold period. Less striking effects were observed for plant developmental rate, final leaf number, RUE and leaf inclination. Virtual plants simulating the architecture of the genotypes both in early and normal sowings were generated and used to evaluate the effect of individual traits on light capture. The results presented here are a first step to provide a phenotyping tool of plant response to low temperatures based on virtual plants. Such a tool should help to assess structural (light interception) and functional (RUE) traits that could then be used in segregating populations for genetic studies.