ABSTRACT
The root is the main channel for water and nutrient uptake in plants. Optimisation of root architecture provides a viable strategy to improve nutrient and water uptake efficiency and maintain crop productivity under water-limiting and nutrient-poor conditions. We know little, however, about the genetic control of root development in wheat, a crop supplying 20% of global calorie and protein intake. To improve our understanding of the genetic control of root development in wheat, we conducted a high-throughput screen for variation in seminal root number using an exome-sequenced hexaploid wheat mutant population. The screen identified eight independent mutants with homozygous and stably inherited altered seminal root number (arn) phenotypes, referred to as arn1 to arn8. One mutant, arn1, displays a recessive extra seminal root number phenotype, while six mutants (arn2, arn4 to arn8) show dominant lower seminal root number phenotypes. We show that the lower seminal root number phenotype of arn2, arn4 to arn8 originates from defects in the formation and activation of seminal root primordia. Segregation analysis in F2 populations suggest that the arn1 phenotype is controlled by multiple genes whereas the arn2 phenotype fits a 3:1 mutant:wild-type segregation ratio characteristic of dominant single gene action. This work highlights the potential to use the sequenced wheat mutant population as a forward genetic resource to uncover novel variation in agronomic traits, such as seminal root architecture. Characterisation of the mutants and identification of the genes defining this variation should aid our understanding of root development in wheat.
Footnotes
In this revised version we have included anatomical characterisation of seminal root primordia in the arn mutants.