Onion and other Allium vegetables have been valued since antiquity for their pungent flavor and aroma. Modern science has confirmed traditional benefits that the organosulfur compounds that impart flavor also confer significant human health benefits such as reduced blood clotting and antimicrobial properties. Glucose, fructose and sucrose comprises majority of onion bulb dry matter content. The sugars, pyruvic acid accumulation and transcript level of some transcription factors involved in the biosynthesis of high sugars and pyruvic acid. These profiles were compared with two different lines 36101 (early) and 36122(Late) of bulb onion (Allium cepa L.) growing under drought and photoperiod condition using High Performance Liquid Chromatography (HPLC) and Quantitative real time PCR using FT genes. We identified the gene AcFT4 was responsible for early and late bulb intiation in the onion lines. The cultivar lines 36101and 36122 were used to identify potential genes controlling pungency and sugar. The comparative analysis of two lines showed significant positive phenotypic and genetic correlations. Sugar and pungency profile showed significant difference between two lines. FT gene expression and pungency level was high in onion lines during drought stress. In this study, we proposed the biochemical characterization of two line and genes involved in the bulb formation were also studied. There is a correlation between sugars and pungency level during the drought stress. These results could be presumably used as useful information to obtain onion varieties rich in sugars and pungency.