Abstract
Pearl millet is able to withstand dry and hot conditions and plays an important role for food security in arid and semi-arid areas of Africa and India. However, low soil fertility and drought constrain pearl millet yield. One target to address these constraints through agricultural practices or breeding is root system architecture. In this study, in order to easily phenotype the root system in field conditions, we developed a model to predict root length density (RLD) of pearl millet plants from root intersection densities (RID) counted on a trench profile in field conditions. We identified root orientation as an important parameter to improve the relationship between RID and RLD. Root orientation was notably found to depend on soil depth and to differ between thick roots (more anisotropic with depth) and fine roots (isotropic at all depths). We used our model to study pearl millet root system response to drought and showed that pearl millet reorients its root growth toward deeper soil layers that retain more water in these conditions. Overall, this model opens ways for the characterization of the impact of environmental factors and management practices on pearl millet root system development.
Highlights
IntroductionIt is well adapted to dry tropical climate and low-fertility soils and plays an important role for food security in arid and semi-arid regions of sub-Saharan Africa and India
During the development and calibration of the model, we observed that pearl millet root growth orientation was only dependent on soil depth as already observed for other Poaceae species [13, 14]
The growth orientation of fine roots, which most likely corresponded to the different types of laterals [16,30], was only marginally dependent on soil depth
Summary
It is well adapted to dry tropical climate and low-fertility soils and plays an important role for food security in arid and semi-arid regions of sub-Saharan Africa and India. In these areas, pearl millet is an important source of nutritious food [2, 3] and is the staple crop for nearly 100 million people [4, 1]. The recent sequencing of a reference genome and about 1, 000 accessions [4] open the way for a new era of genomic-based breeding in pearl millet [8]. This will depend on the availability of phenotyping methods to characterize and exploit the available genetic diversity and identify interesting target traits
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