Micronutrient fortification of potatoes using metal oxide nanoparticles

The project aimed to increase the phytoavailability of calcium (Ca), iron (Fe) and zinc (Zn) in potato tubers, and assess the impact on disease (soft rot) incidence. It involved the use of metal oxide nanoparticles  (MONP) coated with the amino acid histidine (MONP+His). Because of  the size of the nanoparticles,  they can potentally penetrate through the cell wall pores into the plant. The histidine coating facilitates this movement. Mineral uptake was observed initially in hydroponic systems, followed by greenhouse and polytunnel conditions and then field trials utilising the iron oxide nanoparticle. Growth rates, tuber number, size and fresh weight were recorded along with dry matter analysis and the mineral content of tubers. The retention of the metal oxide nanoparticles (MONP) in the soil was also studied. 

Results

An increase in mineral content was observed when the particles (MONP) were applied to potato, both as a solution to the soil and by foliar application. The optimal concentration of MONP+His differed between varieties and with different trial environments. Tubers gained significant amounts of Ca but the size of the increase was lower than for other applied MONP. Data from segregated areas of the tuber showed the translocation and potential utilisation of Fe sources from the nanoparticle throughout the plant. A high proportion of Fe was retained in the tuber skin. The application of ‘FeNP+His. 16 mg / L’ in  trials significantly increased the Fe concentration in the skin and tuber itself compared to other treatments. The increase in Zn content in tubers increased with increasing ZnNP+His. application, however, foliar growth was severely stunted when treated with ZnNP+His., indicating a phytotoxic effect of ZnNP in the hydroponic system. In some cases, there were reductions in the number of pectolytic bacteria recorded when swabs were taken from the surface of treated tubers, but overall numbers of bacteria in potato peel samples were unaffected after tubers had been soaked in MONP solutions.