9Drought, heat, high temperature, waterlogging, low-N stress, and salinity are the major 10 environmental constraints that limit plant productivity. In tropical regions maize grown during the 11 summer rainy season, and often faces irregular rains patterns, which causes drought, and 12 waterlogging simultaneously along with low-N stress and thus affects crop growth and 13 development. The two maize genotypes CML49 and CML100 were subjected to combination of 14 abiotic stresses concurrently (drought and low-N / waterlogging and low-N). Metabolic profiling of 15 leaf and roots of two genotypes was completed using GC-MS technique. The aim of study to reveal 16 the differential response of metabolites in two maize genotypes under combination of stresses and 17 to understand the tolerance mechanism. The results of un-targeted metabolites analysis show, the 18 accumulated metabolites of tolerant genotype (CML49) in response to combined abiotic stresses 19 were related to defense, antioxidants, signaling and some metabolites indirectly involved in nitrogen 20 restoration of the maize plant. Alternatively, some metabolites of sensitive genotype (CML100)
21were regulated in response to defense, while other metabolites were involved in membrane 22 disruption and also as the signaling antagonist. Therefore, the present study provides insight into the 23 molecular mechanisms of tolerance under various stresses of maize plants, that governed on the 24 regulation of cell wall remodeling, maintain metabolic homeostasis, defense against the pathogen,
25proper signaling, and restore growth under stress conditions. 26 27 29 30 Abbrevations: 31 GC-MS-Gas chromatography mass spectrometry32 Low-N-Low nitrogen stress 33 DAS-Days after sowing 34 PCA-Principal component analysis 35 . 36 37 2 1. Introduction 38 Crop faces various stresses in their life span including abiotic and biotic. Several abiotic stresses 39 that affect crop growth, and development are drought, waterlogging, low nutrient availability, 40 salinity, high temperature and heat. The predicted changes in the global climate has accentuate in 41 the frequency and intensity of abiotic factors, most of the abiotic stresses occur in combination, for 42 instant, in tropical area's terminal drought and waterlogging occurs simultaneously during summer-43 rainy season. Although on many occasions the stresses are for shorter duration and relatively mild 44 in nature, but have a significant impact on plant growth and development. Therefore, co-occurrence 45 of abiotic stresses are more destructive to crops than their separate occurrence at different crop 46 growth stages (Mittler 2006; Prasad et al 2011). Besides, the composite responses of plants due to 47 various concurrent stresses rely on signals, these varied and contrast signals may interact with each 48 other to enhanced or obstruct one another (Vile et al. 2012; Suzuki et al. 2014). Maize is the most 49 important cereal, grown at the wide geographical ranges of latitude and longitude. In South Asia, 50 particularly in tropi...