Abstract
Nitrogen use efficiency (NUE) in crops is generally low, with more than 60% of applied nitrogen (N) being lost to the environment, which increases production costs and affects ecosystems and human habitats. To overcome these issues, the breeding of crop varieties with improved NUE is needed, requiring efficient phenotyping methods along with molecular and genetic approaches. To develop an effective phenotypic screening method, experiments on wheat varieties under various N levels were conducted in the automated phenotyping platform at Plant Phenomics Victoria, Horsham. The results from the initial experiment showed that two relative N levels—5 mM and 20 mM, designated as low and optimum N, respectively—were ideal to screen a diverse range of wheat germplasm for NUE on the automated imaging phenotyping platform. In the second experiment, estimated plant parameters such as shoot biomass and top-view area, derived from digital images, showed high correlations with phenotypic traits such as shoot biomass and leaf area seven weeks after sowing, indicating that they could be used as surrogate measures of the latter. Plant growth analysis confirmed that the estimated plant parameters from the vegetative linear growth phase determined by the “broken-stick” model could effectively differentiate the performance of wheat varieties for NUE. Based on this study, vegetative phenotypic screens should focus on selecting wheat varieties under low N conditions, which were highly correlated with biomass and grain yield at harvest. Analysis indicated a relationship between controlled and field conditions for the same varieties, suggesting that greenhouse screens could be used to prioritise a higher value germplasm for subsequent field studies. Overall, our results showed that this phenotypic screening method is highly applicable and can be applied for the identification of N-efficient wheat germplasm at the vegetative growth phase.
Highlights
Over the past five decades, there has been a significant increase in global food production resulting, in part, from the major contribution of substantial nitrogen (N) fertilizer application
Data showed that wheat varieties responded differentially to the supplied N leading to a significant N and variety interaction (Table 2)
Our results demonstrated that the performance of wheat varieties could be assessed effectively at early vegetative stages, as plant status during the linear growth phase truly reflects the potential at maturity regarding DW and grain yield (GY)
Summary
Over the past five decades, there has been a significant increase in global food production resulting, in part, from the major contribution of substantial nitrogen (N) fertilizer application. 110 million metric tons of synthetic N fertilizers are used annually for farming and food crop production globally (International Fertilizer Industry Association, 2013). Nitrogen use efficiency (NUE) is generally low, with only 40% of applied N being taken up by the crop plants, while the remainder is lost to the environment resulting in increased production costs and environmental pollution (Good and Beatty, 2011; Nguyen et al, 2015), as well as affecting human health (Ahmed et al, 2017). Proper N fertilization management practices are expected to reduce N fertilizer application while maintaining stable crop production (Good et al, 2004; Good and Beatty, 2011). To achieve this, improving NUE in crops is one of the most effective ways to ensure current crop yields can be maintained while N supply is reduced, or increasing crop yields with an optimum N input (Cormier et al, 2013)
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