Investigating root traits for drought adaptation in barley: an insight into the genetics influencing root system architecture

Abstract

Environmental events, such as drought, are predicted to increase in frequency and duration, and coupled with an expanding global population, improving cereal crop productivity and yield stability is crucial. A body of research suggests that roots may be fundamental to increasing crop yields, whereby optimised root systems could capture more water and nutrients with minimal metabolic costs. For efficient resource capture in most water-limited environments, a narrow and deep root architecture is likely advantageous. The central importance of the root system in plant productivity cannot be underestimated, yet the functional and genetic basis of root system architecture in cereal crops is relatively unknown.In this thesis, the genetics underpinning root system architecture in barley (Hordeum vulgare L.) were investigated and the value of roots as a drought adaptive trait in barley was examined. In addition, the genetic variation in delayed-foliar senescence and flowering time were also explored to investigate any shared genetic control between above- and below-ground drought adaptation traits. Through the characterisation of three diverse barley populations, key genes influencing root system architecture were identified. Preliminary evidence for shared genetic control between delayed foliar senescence and root architecture was observed through co-located quantitative trait loci (QTL), specifically the gibberellic acid biosynthesis gene, Hv20ox1. Preliminary associations between time to flowering and seminal root traits were confirmed through the identification of VERNALIZATION1 (VRN1) as a major gene influencing root architecture in barley. Whereby, VRN1 is a key regulator of flowering behaviour in cereal crops. The research described in this thesis provides novel insight into the genetic control of root system architecture and reveals a new role for the previously described pathway for regulation of flowering in modulating the largely unexplored genetic architecture of root development in barley. The knowledge generated from this research may be harnessed in barley breeding programs to assist in the development of robust cultivars better adapted to the increasingly variable future climate.