Linking fundamental science to crop improvement through understanding source and sink traits and their integration for yield enhancement

Abstract

Understanding processes in sources and sinks that contribute to crop yields has taken years of painstaking research. For crop yield improvement, processes need to be understood as standalone mechanisms in addition to how these mechanisms perform at the crop level; currently there is often a chasm between the two. Fundamental mechanisms need to be considered in the context of crop ideotypes and the agricultural environment which is often more water limited than carbon limited. Different approaches for improvement should be considered, namely is there genetic variation? Or if not, could genetic modification, genome editing, or alternative approaches be utilized? Currently, there are few examples where genetic modification has improved intrinsic yield in the field for commercial application in a major crop. Genome editing, particularly of negative yield regulators as a first step, is providing new opportunities. Here we highlight key mechanisms in source and sink, arguing that for large yield increases integration of key processes is likely to produce the biggest successes within the framework of crop ideotypes with optimized phenology. We highlight a plethora of recent papers that show breakthroughs in fundamental science and the promise of the trehalose 6-phosphate signalling pathway, which regulates carbohydrate allocation which is key for many crop traits.

Trehalose 6-phosphate signalling and impact on crop yield

“…Such knowledge could help refine crop improvement by T6P and provide strategies to modify T6P levels up or down and or alter the perception and signalling of T6P. There are of course other genes in source and sinks that have shown utility in crop improvement particularly in hormone signalling pathways and several transcription factors already mentioned [20,29,48]. It will be interesting to better understand how the T6P pathway interacts with, is regulated by, or regulates any of these other systems.…”

Gene-based mapping of trehalose biosynthetic pathway genes reveals association with source- and sink-related yield traits in a spring wheat panel

“…The T6P signalling pathway ( Figure 1a) is a central regulatory system of resource allocation and source-sink interactions and is emerging as an important target in crops such as maize, rice, wheat, and sorghum (Paul et al, 2018;Paul et al, 2020). Here for the first time we analysed comprehensive exome SNP information for TPS and TPP genes and dissected the genetic architecture of yield-related traits in a spring wheat diversity panel where all lines presented acceptable agronomic performance (Molero et al, 2019).…”

“…Likewise, our results also revealed strong pleiotropic effects ( Figure 2; Table 1). This can likely be explained by changes in whole plant carbon allocation which may affect more than one trait, particularly for pathways like trehalose that regulates carbohydrate allocation (Paul et al, 2018;Paul et al, 2020). Previous studies have reported pleiotropy for other phenotypes (e.g.…”

“…In recent decades, numerous studies in bread wheat (Triticum aestivum L.) have focused on relations between the source (the supply of assimilates) and the sink (the capacity to accumulate available carbohydrates) with the aim to increase genetic gains (Reynolds et al, 2017). A pathway within crops that has been associated with source-and sink-related traits is the trehalose biosynthetic pathway consisting of trehalose phosphate synthase (TPS) and trehalose phosphate phosphatase (TPP) genes (Lunn, 2007;Lunn et al, 2014;Paul et al, 2018;Paul et al, 2020).…”

Identification of quantitative trait loci for dynamic and steady-state photosynthetic traits in a barley mapping population

“…By 2050, the global population is expected to rise to 9 billion and to meet future food demand we will need to increase crop production worldwide by 70 % ( Paul et al 2019 ). Recent progress has been hindered by stagnating rates of annual yield increase; therefore, novel breeding targets to improve crop yield potential are urgently needed.…”