Abstract
AimsSelection for optimal root system architecture (RSA) is important to ensure genetic gains in the sustainable production of wheat (Triticum aestivum L.). Here we examine the hypothesis that past wheat breeding has led to changes in RSA and that future breeding efforts can focus directly on RSA to improve adaptation to target environments.MethodsWe conducted field trials using diverse wheat varieties, including modern and historic UK varieties and non-UK landraces, tested under contrasting tillage regimes (non-inversion tillage versus conventional ploughing) for two trial years or different seeding rates (standard versus high rate) for one trial year. We used field excavation, washing and measurement of root crowns (‘shovelomics’) to characterise RSA traits, including: numbers of seminal, crown and nodal roots per plant, and crown root growth angle.ResultsWe found differences among genotypes for all root traits. Modern varieties generally had fewer roots per plant than historic varieties. On average, there were fewer crown roots and root angles were wider under shallow non-inversion tillage compared with conventional ploughing. Crown root numbers per plant also tended to be smaller at a high seeding rate compared with the standard. There were significant genotype-by-year, genotype-by-tillage and genotype-by-seeding-rate interactions for many root traits.ConclusionsSmaller root systems are likely to be a result of past selection that facilitated historical yield increases by reducing below-ground competition within the crop. The effects of crop management practices on RSA depend on genotype, suggesting that future breeding could select for improved RSA traits in resource-efficient farming systems.
Highlights
Increasing global human population growth, combined with challenges due to climate change and resource depletion, means that agriculture must become more productive and efficient while contributing fewer greenhouse gas emissions (Conijn et al, 2018; Smith et al, 2007)
The effects of crop management practices on root system architecture (RSA) depend on genotype, suggesting that future breeding could select for improved RSA traits in resource-efficient farming systems
A highly significant genotype effect was found for seminal root number (SRN) among the 16 NIAB Diverse multi-founder advanced generation inter-cross (MAGIC) founders grown at Duxford but was only marginally significant among the 20 WHEALBI accessions grown at Sonning
Summary
Increasing global human population growth, combined with challenges due to climate change and resource depletion, means that agriculture must become more productive and efficient while contributing fewer greenhouse gas emissions (Conijn et al, 2018; Smith et al, 2007). Plant breeders have largely neglected direct selection for wheat root traits This is in part due to the relative inaccessibility of roots, their phenotypic plasticity, and the absence of high-throughput screening methods (Manschadi et al, 2006). Current root phenotyping methods have mostly focused on root traits in young plants under controlled environments (Atkinson et al, 2015; Kuijken et al, 2015; Richard et al, 2015; Watt et al, 2013). These techniques do not reflect real soil conditions in the field, and inconsistent results are often found between methods (Wojciechowski et al, 2009). Current RSA phenotyping methods in field conditions are slow, laborious and prone to excessive variation (Gregory et al, 2009)
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