Impacts of G x E x M on Nitrogen Use Efficiency in Wheat and Future Prospects

Abstract

Globally it has been estimated that only one third of applied N is recovered in the harvested component of grain crops. This represents an incredible waste of resource and the overuse has detrimental environmental and economic consequences. There is substantial variation in nutrient use efficiency (NUE) from region to region, between crops and in different cropping systems. As a consequence, both local and crop specific solutions will be required for NUE improvement at local as well as at national and international levels. Strategies to improve NUE will involve improvements to germplasm and optimized agronomy adapted to climate and location. Essential to effective solutions will be an understanding of genetics (G), environment (E), and management (M) and their interactions (G x E x M). Implementing appropriate solutions will require agronomic management, attention to environmental factors and improved varieties, optimized for current and future climate scenarios. As NUE is a complex trait with many contributing processes, identifying the correct trait for improvement is not trivial. Key processes include nitrogen capture (uptake efficiency), utilization efficiency (closely related to yield), partitioning (harvest index: biochemical and organ-specific) and trade-offs between yield and quality aspects (grain nitrogen content), as well as interactions with capture and utilization of other nutrients. A long-term experiment, the Broadbalk experiment at Rothamsted, highlights many factors influencing yield and nitrogen utilization in wheat over the last 175 years, particularly management and yearly variation. A more recent series of trials conducted over the past 16 years has focused on separating the key physiological sub-traits of NUE, highlighting both genetic and seasonal variation. This perspective describes these two contrasting studies which indicate G x E x M interactions involved in nitrogen utilization and summarizes prospects for the future including the utilization of high throughput phenotyping technology.

Durum Wheat Grain Yield and Quality under Low and High Nitrogen Conditions: Insights into Natural Variation in Low- and High-Yielding Genotypes

“…The resulting components, N 2 , CO 2 , H 2 O, and SO 2 were separated in a chromatographic column (Porapak 2m, Santa Clara, CA, USA) and detected with a thermal conductivity detector. Nitrogen use efficiency (NUE) of production was determined as the ratio of grain yield to the total N concentration in grains, which must be differentiated from other ways of measuring the efficiency of N use by plants [71].…”

Defining the physiological determinants of low nitrogen requirement in wheat

“…This can be problematic as tillers that emerge later during development compete for light and nutrients [ 43 , 44 ], and surplus late tillers tend to die back or be less productive than early tillers. This may ultimately lead to a lower yield per unit of N (also defined as N use efficiency, NUE) when plants are grown under high vs low N conditions [ 10 , 45 , 46 ].…”

Targeting Nitrogen Metabolism and Transport Processes to Improve Plant Nitrogen Use Efficiency

“…However, progress in NUE is an ambitious target as crop yields are influenced by numerous factors, including genetic parameters and their variation among and within species (G), environmental effects such as location, soil conditions, and climate (E), and agronomic technologies and management practices (M; e.g., type, timing, amount, and place of N application or weed and pest control) (Hatfield and Walthall, 2015 ; Nguyen et al, 2017 ; Martinez-Feria et al, 2018 ; Nguyen and Kant, 2018 ; Gramma et al, 2020 ; Jensen et al, 2020 ; Lemaire and Ciampitti, 2020 ; Plett et al, 2020 ). Only the combination or interaction of these factors (G × E × M) will allow for sustainable and secure crop production (Swarbreck et al, 2019 ; Cooper et al, 2020 ; Hawkesford and Riche, 2020 ; Peng et al, 2020 ).…”