Micronutrient trait/efficiency is a measure of the quantity of micronutrient present in harvested grains. Modern breeding practices have diluted micronutrient content in wheat grains significantly compared to historic varieties. In addition, a large proportion of Western Australian cropping soils are Zn deficient causing lesser Zn accumulation in grains. Improving Zn uptake and mobilization in grains through genetic biofortification present a sustainable solution.

The objective of the present study is to identify Zn-efficient lines both on +Zn and -Zn conditions in Western Australian soils. A selective subset of objective-specific international micronutrient panel containing introgressions of Triticum with wild relatives and landraces has been screened at Merredin in 2023 on a slightly alkaline (pH 7.4), Zn deficient (0.28 ppm) sandy loam paddock. A split-plot trial with +Zn and -Zn as main plots and varieties as subplots was used. Inductively coupled plasma mass spectrometry (ICP-MS) test was carried out on harvested grains, stems, and rachis to assess micronutrient content.

The genotypes were ranked in -Zn and +Zn plots based on grain Zn content. The zinc concentration ranged from 20.1 to 34.5 mg/kg and 32.7 to 58.5 mg/kg in -Zn and +Zn plots, respectively. HarvestPlus Zn target for healthy wheat is 33 mg/kg and recommended daily allowance is 45 mg/kg grains. In -Zn condition, six genotypes had higher grain Zn compared to WA check variety Scepter (28.8 mg/kg) with the highest one having 34.5 mg/kg Zn. In +Zn condition two genotypes were ranked above, and seven genotypes were in comparable range with Scepter (54.4 mg/kg). Manganese (Mn) and iron (Fe) were positively correlated with Zn. Zn mobilization from stem and rachis to grains was higher in high-Zn lines compared to low-Zn lines.

We have ongoing second round of screening using same set of lines in Merredin to validate the potential Zn-efficient lines. In conclusion, Zn-efficient lines will benefit wheat breeding programs to develop new genetically biofortified cultivars suitable for WA environment, build reputation of WA wheat in international market and boost exports and economic returns. 

References:

Rob Norton. GRDC Update paper (2014). What’s new with zinc; maybe just some critical reminders? 

Rob Norton. Keeping an eye on zinc levels (2011), Australia and New Zealand, International Plant Nutrition Institute. http://anz.ipni.net/article/ANZ-3081 

Cakmak, Ismail, Wolfgang H. Pfeiffer, and Bonnie McClafferty. "Biofortification of durum wheat with zinc and iron." Cereal chemistry 87, no. 1 (2010): 10-20. 

Fan, Ming-Sheng, et al. "Evidence of decreasing mineral density in wheat grain over the last 160 years." Journal of Trace Elements in Medicine and Biology 22.4 (2008): 315-324.