Abstract
Phenotypic measurements under controlled cultivation conditions are essential to gain a mechanistic understanding of plant responses to environmental impacts and thus for knowledge-based improvement of their performance under natural field conditions. Twenty maize inbred lines (ILs) were phenotyped in response to two levels of water and nitrogen supply (control and stress) and combined nitrogen and water deficit. Over a course of 5 weeks (from about 4-leaf stage to the beginning of the reproductive stage), maize phenology and growth were monitored by using a high-throughput phenotyping platform for daily acquisition of images in different spectral ranges. The focus of the present study is on the measurements taken at the time of maximum water stress (for traits that reflect plant physiological properties) and at the end of the experiment (for traits that reflect plant architectural and biomass-related traits). Twenty-five phenotypic traits extracted from the digital image data that support biological interpretation of plant growth were selected for their predictive value for mid-season shoot biomass accumulation. Measured fresh and dry weights after harvest were used to calculate various indices (water-use efficiency, physiological nitrogen-use efficiency, specific plant weight) and to establish correlations with image-derived phenotypic features. Also, score indices based on dry weight were used to identify contrasting ILs in terms of productivity and tolerance to stress, and their means for image-derived and manually measured traits were compared. Color-related traits appear to be indicative of plant performance and photosystem II operating efficiency might be an importance physiological parameter of biomass accumulation, particularly under severe stress conditions. Also, genotypes showing greater leaf area may be better adapted to abiotic stress conditions.
Highlights
Nitrogen and water, separately or in combination, are two of the most critical factors in maize production worldwide
In this study we focused on the measurements done at the phase of maximal water stress and at the end of the cultivation period with two main objectives: (i) to identify reliable and useful image-based traits for mid-season biomass accumulation in each treatment and (ii) to identify contrasting genotypes in a terms of biomass productivity for each stress type with image-derived and manually measured traits contributing to stress tolerance
V-273 (IL4) is a commercial line developed at the Maize Research Institute Zemun Polje (MRIZP), Serbia and represents a prolific version of B73 inbred
Summary
Separately or in combination, are two of the most critical factors in maize production worldwide. High-Throughput Phenotyping of Maize yield reduction, respectively, has been reported to be attributed to irreversible effects of delayed nitrogen application at the 6- and 10-leaf stages (Binder et al, 2000; Walsh et al, 2012). Short-term water deficits during rapid vegetative growth caused up to 40% grain yield losses which was explained by a decline in plant extension growth and a reduction of leaf size (Çakir, 2004). The responses of plants to a combination of water and nitrogen stress may even cause further effects beyond the individual impacts, and cannot be directly extrapolated from conclusions obtained from the different stresses applied individually (Humbert et al, 2013). Several studies showed that it was possible to improve maize germplasm for simultaneous expression of tolerance to mid-season drought and nitrogen stress through recurrent selection (Bänziger et al, 2002; Zaidi et al, 2004)
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