Impact of biofertiliser and zinc nanoparticles on enzymatic, biochemical, and agronomic properties of sugar beet under different irrigation regimes

To investigate the enzymatic, biochemical, and agronomic response of sugar beet ( Beta vulgaris L.) to biofertilisers and zinc nanoparticles under different irrigation regimes, an experiment was conducted at the Agricultural and Natural Resources Research Station of Miandoab, West Azerbaijan Province, Iran. Three irrigation levels: normal, mild stress, and severe water stress, were applied (control – without irrigation) in the main plots, and three fertilisation treatments: seed inoculation with arbuscular mycorrhizal fungi (AMF), zinc nano-oxide nanoparticles (ZnO NPs), and AMF + ZnO NPs, were applied (control – without fertilisers) in the sub-plots in two years. The severe water stress reduced the content of chlorophyll a , b , and carotenoids by 14.53, 8.09, and 22.11 %, respectively, and increased the content of leaf flavonoids and superoxide dismutase (SOD) by 34.17% and 33.14%, respectively, compared to normal irrigation. The AMF + ZnO NPs treatment increased the content of chlorophyll a , chlorophyll b , carotenoids, and SOD by 36.76, 12.61, 10.36, and 10.18 %, respectively, compared to the control treatment. The highest root yield, sugar yield, and white sugar yield provided the AMF + ZnO NPs treatment under normal irrigation. The highest proline content, total phenolic content (TPC), catalase (CAT) activity, sugar content, and white sugar content were found in sugar beets treated with AMF + ZnO NPs under severe water stress. The AMF + ZnO NPs treatment under normal irrigation and mild water stress and ZnO NPs one under severe water stress increased the white sugar yield by 42.67, 55.69, and 20.11 %, compared to the control treatment. Thus, treating with AMF + ZnO NPs under normal and mild water stress and applying of ZnO NPs under severe water stress can be a solution to increase the economic yield of sugar beet.