Executive Summary : | Maize is the third most important cereal crop in the world next to rice and wheat with diverse use as food, feed and industrial use. However, traditional maize is poor in essential amino acids, provitamin-A, α-tocpherol and oil content, affecting growth, development, visual & immune system and neurological functions. Further, these nutrients increase body weight and requires less feed in poultry birds; and gets accumulated more vitamins in egg yolks, thereby making the eggs more nutritious. Research efforts at the ICAR-Indian Agricultural Research Institute, New Delhi has led to development of series of multi-vitamin (provitamin-A & provitamin-E) rich QPM hybrids through marker-assisted introgression of β-carotene hydroxylase (crtRB1), lycopene-ε-cyclase (lcyE), γ-tocopherol methyl transferase (vte4) and opaque2 (o2) genes (Muthusamy et al. 2014; Zunjare et al. 2018; Das et al. 2021). These hybrids possess high lysine (0.30-0.40%), tryptophan (0.08-0.10%), provitamin-A (10-12 ppm) and α-tocopherol (16-18 ppm). Oil is considered to be a factor that increases the bioavailability of vitamin-A and vitamin-E. Thus, the value of biofortified multi-vitamin maize hybrids will surge with rise in oil content. Besides, due to high protein quality and metabolizable energy in maize oil, it becomes an important additive for livestock feed. Further efforts at IARI, New Delhi have led to the development of high oil (6-8%) maize rich in multi-vitamins (Katral et al. 2021). Even though, these high oil maize genotypes are rich in multi-nutrients with better quality oil, degradation of carotenoids and tocopherols during storage is a major issue. Of the factors causing seed deterioration, lipid peroxidation leads to negative effect of high oil, attributed to lipoxygenase isoenzymes (LOXs) (Chedea and Jisaka 2013). LOXs are a large group of monomeric dioxygenase proteins containing non-heme, non-sulphur and iron cofactor, that . causes oxidation of PUFA like linoleic and linolenic to yield free radicals and hydroperoxides, and makes the oil rancid (Borrego and Kolomiets 2016). Kernel and germ tissues contained 75% of the lipoxygenase activity with rest of the activity found in the outer cob (Boyes et al. 1992). A total of 13 LOX genes were reported in maize genome, of which LOX3 gene has been reported to play a major role (Ogunola et al. 2017). Thus, free radical production is expected to be more in maize embryo due to the higher activity of LOXs, particularly LOX3 (Poca et al. 1990). Down-regulation of LOX enzyme activity promoted higher retention of carotenoids in biofortified rice during storage (Gayen et al. 2015). Hence, LOX could be effectively used as potent tool to improve the keeping quality of maize oil with adequate retention of tocopherols and carotenoids during post-harvest storage and processing. The project aims to assess genetic variation for lipoxygenase activity and molecular characterisation of LOX3 gene for reducing rancidity in high oil maize. |