Variation in grain Zn concentration, and the grain ionome, in field-grown Indian wheat

Wheat is an important dietary source of zinc (Zn) and other mineral elements in many countries. Dietary Zn deficiency is widespread, especially in developing countries, and breeding (genetic biofortification) through the HarvestPlus programme has recently started to deliver new wheat varieties to help alleviate this problem in South Asia. To better understand the potential of wheat to alleviate dietary Zn deficiency, this study aimed to characterise the baseline effects of genotype (G), site (E), and genotype by site interactions (GxE) on grain Zn concentration under a wide range of soil conditions in India. Field experiments were conducted on a diverse panel of 36 Indian-adapted wheat genotypes, grown on a range of soil types (pH range 4.5–9.5), in 2013–14 (five sites) and 2014–15 (six sites). Grain samples were analysed using inductively coupled plasma-mass spectrometry (ICP-MS). The mean grain Zn concentration of the genotypes ranged from 24.9–34.8 mg kg-1, averaged across site and year. Genotype and site effects were associated with 10% and 6% of the overall variation in grain Zn concentration, respectively. Whilst G x E interaction effects were evident across the panel, some genotypes had consistent rankings between sites and years. Grain Zn concentration correlated positively with grain concentrations of iron (Fe), sulphur (S), and eight other elements, but did not correlate negatively with grain yield, i.e. no yield dilution was observed. Despite a relatively small contribution of genotype to the overall variation in grain Zn concentration, due to experiments being conducted across many contrasting sites and two years, our data are consistent with reports that biofortifying wheat through breeding is likely to be effective at scale given that some genotypes performed consistently across diverse soil types. Notably, all soils in this study were probably Zn deficient and interactions between wheat genotypes and soil Zn availability/management (e.g. the use of Zn-containing fertilisers) need to be better-understood to improve Zn supply in food systems

Grain and shoot zinc accumulation in winter wheat affected by nitrogen management

Background and aims Nitrogen (N) nutrition is a critical factor in zinc (Zn) acquisition and its allocation into grain of wheat (Triticum aestivum L.). Most of the information collected about this topic is, however, derived from the pot experiments. It is also not known whether optimal N management by decreasing N input could affect the Zn status in grain and plant in the field. The aim of this research is to investigate the impact of N management on grain and shoot Zn status of winter wheat. Methods Field experiments were conducted in two cropping seasons. Results Results showed applying N at optimal rate (198 kg N ha(-1) in 2007-2008 and 195 kg N ha(-1) in 2008-2009) maintained or resulted in significantly higher grain Zn concentration and especially grain content of Zn compared to no or lower N treatments. For example, grain Zn concentration increased from 21.5 mg kg(-1) in the control to 30.9 mg kg(-1) with optimized N supply in 2007-2008 and from 24.7 mg kg(-1) in the control to 29.1 mg kg(-1) with optimized N supply in 2008-2009. Further increasing N supply from optimal to excessive N supply resulted in non-significant increases in grain Zn concentration and content. Generally, similar trends were also found in shoot Zn. Moreover, 72 % to 100 % of the shoot Zn requirement had been accumulated at anthesis, and accordingly 67 % to 100 % of grain Zn content was provided by Zn remobilization from pre-anthesis Zn uptake with N supply. Grain Zn accumulation mainly originates from Zn remobilization and the optimal N management would ensure better shoot Zn nutrition to contribute to increasing Zn remobilization from vegetative tissues and to maintain relatively higher grain Zn for better human nutrition