Role of soil total nitrogen in aroma synthesis of traditional regional aromatic rice in China

BACKGROUND AND AIMS: Aromatic rice (Oryza sativa L.) is warmly welcomed world-wide. Previous research showed contradictory evidence on whether or not nitrogen is an environmental factor in producing high quality aromatic rice. So it is necessary to clarify the role of nitrogen in aroma synthesis of traditional Chinese regional aromatic rice. METHODS: By sensory analysis and GC–MS analysis coupled with alternative moving window factor analysis (AMWFA), aromas were qualified and quantified. Aromatic rice cultivars named Basmati, Xiangwanxian#13, Zhongxiang#1 and non-aromatic rice cultivar named Huanghuazhan were chosen. Two experiments were conducted in three locations on five kinds of paddy fields. One experiment was designed as a Split-Split-plot with four replications in traditional regional aromatic rice production field (APF) and common paddy field (CPF). APF and CPF located in Jiangyong County and Yongshun County. The second experiment was a completely randomized design with four rice cultivars with four replications in Changsha City. RESULTS: Results showed that: (1) higher total soil nitrogen content corresponds to higher l-proline content and total nitrogen (protein) content of the brown rice; (2) higher total soil nitrogen content corresponds to lower soluble protein content of the brown rice; (3) the stronger the aroma of the rice grain, the greater the l-proline and total nitrogen content with lower soluble protein found in the brown rice; and (4) the higher the total nitrogen content of the soil, the stronger the aroma of the grain. CONCLUSIONS: Total soil nitrogen is one of the key factors in producing the aroma of traditional Chinese regional aromatic rice. We can regulate the nitrogen metabolism to strengthen the aroma of the rice as the same as gene modification. In the future we should consider the effect of the salinization of soil on the nitrogen (N) metabolism.