Responses of eating quality related traits to nitrogen application rate for indica rice varieties (lines) from South China

Objective To find the characteristics of responses of eating quality related traits to nitrogen fertilizer application rates and planting seasons, identify rice varieties (lines) with different responding types, screen out fine quality ones which are insensitive to nitrogen application amount, and provide theoretical and technical supports for developing new rice varieties (lines) with fine and stable quality and establishing high-yield and high-quality cultivation techniques.

Method Totally seventeen rice varieties or lines were involved, including high-quality and high-yield conventional and hybird rice varieties, and their parental lines from South China, and four treatments of nitrogen fertilzer application rates (including 0, 90,135 and 180 kg/hm²) were conducted in the early and late cropping seasons, respectively, and the response of cooking and eating quality was observed.

Result 1)Except that the alkali spreading value (ASV) had fewer response, amylose content (AC), protein content (PC) and taste value (TV) all had the obvious response to nitrogen fertilzer application rate, suggesting that the nitrogen fertilizer had significant affect on these quality traits. The PC increased with the increase of nitrogen application, whereas TV decreased with the increase of nitrogen application. There exsisted the interaction effect of nitrogen application level × variety (line) for Gel consistence (GC) in both early and late seasons, and for AC、PC and TV in the late season, suggesting that the effect of nitrogen application rate on AC, GC, PC and TV varied with varieties. 2)In the late season (LS), the rice varieties (lines) treated with no nitrogen fertilizer (N0) usually had the highest taste value, while in the early season (ES), the rice varieties (lines) treated with 90 kg/hm² of nitrogen (N1) generally had the highest taste value, suggesting that a small amount of nitrogen fertilizer should be applied in ES, whereas as far as possible no or very few amount of nitrogen fertilizer applied in LS may be more conducive to improving the taste of rice. 3)Different high-quality rice varieties (lines) had different sensitivity to nitrogen application in rice taste, there exist great differences among varieties. 4)The GC, AC, PC and TV of hybrid F₁ were mostly between their parents. However, their TV tended to the high-value parent, and exhibited partial dominant or overdominant.

Conclusion To develop conventional rice and hybrid rice with good taste, it is necessary to use materials with medium and low PC and higher TV as parents for improving the breeding efficiency of new rice varieties. In the production of high quality rice, selecting high quality rice varieties with good taste and lower sensitivity to nitrogen fertilizer, and matching corresponding fertilization technology program according to the production season, is crucial to the development of high-taste and high-quality rice industry.