A mouthful of fresh and soft rice is memorable. How to improve rice quality while taking into account high rice yield and efficient nitrogen utilization is an important challenge in breeding high-quality rice varieties. 

Recently, Xu Guohua, a professor at the School of Resources and Environment, Nanjing Agricultural University, found that enhancing the expression abundance of a special gene in rice can significantly improve the cooking flavor quality of rice under different levels of nitrogen supply without altering the total length of the reproductive period, nitrogen use efficiency and yield of rice. The results have been published in the international academic journal, Journal of Plant Biotechnology.

Multiple factors affect the cooking flavor of rice

Xu Guohua pointed out that rice varieties, planting environment and cultivation measures all affect the cooking flavor of rice.

"The quality of rice is mainly determined by the variety, and the distinction between varieties mainly comes from the differences in starch and protein content and structure in rice. Different varieties determine that rice taste and cooking characteristics, among other things, will be different." Xu Guohua introduced, the higher the content of straight chain starch, the harder the texture of the rice, the lower the viscosity, rough and dry, lack of luster, poor taste; the lower the content of straight chain starch, the softer the rice and easy to stick into a ball. Therefore, it is generally believed that rice with a medium-low content of straight-chain starch has the best taste.

"The higher the protein content in the rice, the smaller the gap between the starch grains will be, the poorer the quality of the flavor, the cooking process to absorb less water and slow. This will lead to longer cooking time and inability to fully pasturize the rice, poor viscosity of the cooked rice, resulting in poor taste quality." Xu Guohua said.

Secondly, rice planting soil, temperature, light and other differences in the planting environment, as well as fertilization, planting density, water management and other cultivation measures, will have a great impact on the quality of the taste of rice. The high yield and quality of rice is very dependent on the application of nitrogen fertilizer, but the effect of nitrogen fertilizer on the taste quality of rice is very complex. Excessive nitrogen fertilizer not only causes a series of ecological problems, but also reduces nitrogen use efficiency and affects rice quality, especially cooking taste.

"The irrational application of nitrogen fertilizer also tends to cause rice fertility too short or too long, affecting rice photosynthesis and nutrient accumulation, which in turn affects rice quality." Xu Guohua said.

Providing genetic resources to improve rice quality

Xu Guohua's team used molecular biology techniques to analyze the changes of genes in the flower developing organs of rice during the flower lifting stage, under the condition of applying different amounts of nitrogen fertilizer, which resulted in the discovery of the nitrogen-dependent rice tasseling factor, Nhd1. "We found that Nhd1 can regulate the timing of tasseling and flower lifting, the yield of rice, the efficiency of nitrogen utilization, and the taste of rice. " Xu Guohua said.

How can Nhd1 be used to make rice taste and quality better without affecting high rice yield and nitrogen utilization efficiency? "In this study, we utilized Nhd1's own gene fragments to create rice genetic materials whose endogenous expression abundance was dramatically increased." Xu Guohua introduced, the team found that under different levels of nitrogen application, compared with the recipient parental varieties, rice with high Nhd1 expression abundance, rice starch granules are more loosely arranged, and the content of straight-chain starch, pasting temperature, and protein content of rice are also significantly reduced, the gelatin consistency of rice is increased, and the rice is softer and more glutinous after cooking, which improves the cooking flavor quality of rice. Meanwhile, the increase in Nhd1 expression abundance did not change the yield, nitrogen utilization efficiency and fertility of rice. How to achieve the combination of productivity and quality is also one of the topics that sial shenzhen pays close attention to.

In addition, the team also found that rice with higher Nhd1 expression abundance also had better cooking flavor quality in the main cultivars of Jiangsu Province, where rice quality is already relatively high. This suggests that by enhancing the abundance of endogenous Nhd1 in rice, it is possible to effectively improve the flavor quality of rice while ensuring high yields. Xu Guohua said this means that without increasing nitrogen fertilizer input and without affecting rice fertility and yield, the study provides new ideas and genetic resources for molecular improvement of rice quality.

Xu Guohua believes that in the future, breeding experts can consider the expression abundance of Nhd1 and the degree of response to nitrogen fertilizer as an important screening criterion for high-yield and high-quality traits in the selection and breeding of high-quality and palatable varieties of rice. It can also be considered to use it as a molecular marker for the targeted breeding of high-yield rice varieties with excellent cooking flavor quality. If you want to know more about food information, please pay attention to Sial Shenzhen 2024.