Adaptive root plasticity in pearl millet – PlastiMil

Pearl millet is a key cereal for food security in arid and semi-arid regions of West Africa and India. However, climate change is predicted to increase the frequency of extreme events such as dry spells (strong episodes of rain interrupted by long drought periods) that will affect its yield. In this context, improving pearl millet adaptation to drought caused by rainfall uncertainty is needed. Roots represent a target to improve pearl millet adaptation to drought because they are responsible for water uptake and can greatly adapt their development in response to new environments. The changes in phenotypic traits in response to a new environment are called phenotypic plasticity. Such plasticity can be adaptive if it improves the plant ability to adapt to the new environment, for instance by stabilizing other important agronomical traits. Therefore, developing pearl millet varieties that can respond to drought by developing root systems better adapted to water capture and transport water represent an interesting perspective. However, the mechanisms associated with root plasticity remain elusive in pearl millet as well as in other cereals.

The PlastiMil project aims at identifying the genetic determinants and physiological mechanisms associated with root plasticity in response to drought in pearl millet. The Project will use root phenotyping datasets (architecture and anatomy) from a panel of 150 fully-sequenced pearl millet inbred lines obtained during two years of field experiments under irrigated and drought stress conditions. These data will be exploited in order to identify plastic root traits that are variable between lines in response to drought (controlled by the interaction between genotypes and environment) and precisely quantify plasticity of these traits. Root plasticity will be associated with agronomical performance as well as the geographical and climatic origin of each lines in order to infer the adaptive value of the plastic response. Plastic root traits showing variability, heritability and adaptive value will be further associated with the genotypes of each lines in order to identify genetic regions controlling plasticity. Whole gene expression at key steps of the most interesting root plastic response will be studied in order to identify genes controlling plasticity of the corresponding root trait. Two candidate genes for the considered plastic root response will be disrupted and root plasticity will be evaluated in the resulting mutated plants in comparison to wild type line. Mutated plants affected in their plastic response will be used to study the impact of the plastic root trait on pearl millet hydraulics under drought stress by considering root water transport, transpiration and plant water use efficiency.

PlastiMil is an interdisciplinary four years project that will look for plastic root traits in response to drought using approaches coming from the fields of evolution, genetics, functional genomics and physiology. It will provide QTLs/genes useful for breeders to develop new pearl millet varieties better adapted to rainfall uncertainties caused by climate change. This project will be coordinated by Alexandre Grondin in collaboration with young scientists from the University of Nottingham and the Institut Sénégalais des Recherches Agricoles. It will contribute to strengthen an international network of collaborations and establish AG as a scientific leader in the field of crop improvement using root traits.