Physio-biochemical and molecular assessment of Iron (Fe2+) toxicity responses in contrasting indigenous aromatic Joha rice cultivars of Assam, India.

Iron (Fe) toxicity is one of the major abiotic stresses which limits the yield of lowland rice. This study aims to investigate the physiological, biochemical, and molecular aspects of two contrasting aromatic Joha rice, viz., Keteki and Kola Joha of Assam. Oxidative damage caused due to Fe2+ toxicity was quantitatively determined. Fe2+ toxicity in the growth medium increases the level of ROS and anti-oxidative enzyme activity. Along with the aforementioned damage caused due to Fe2+ toxicity, chlorophyll content decreases in both the rice varieties. Detection of Fe3+ and Fe2+ was also conducted by Perls' Prussian and Turnbull blue method, respectively. In addition, spectrophotometric quantification of Fe2+ was determined by 2, 2'-Bipyridyl (Bpy). Above 2.5 mM, Fe2+ toxicity was found to be lethal in rice seedlings affecting their total growth and biomass. Gene expression analysis of iron-regulated transporter 1 (OsIRT1), Yellow Stripe-Like 15 (OsYSL15), and ferritin 1 (OsFer1) revealed the differential gene expression over a time period of Fe2+ toxicity. Our study suggested that the different parameters which are considered here can be helpful for the better understanding of how aromatic Joha rice performed under Fe2+ toxicity which can also help to reveal broader aspects that how gene players are involved in the iron homeostasis mechanism in Joha rice in coming future.