Abstract
Indica-japonica hybrid rice cultivars show great yield potential but poor eating quality and require more nitrogen (N) input relative to japonica rice. However, the effect of N levels on the eating quality of indica-japonica hybrid rice is little known. A field experiment was carried out to investigate the effects of four N levels on two indica-japonica hybrid rice cultivars (Yongyou12 and Yongyou17) differing in eating quality. The results showed that the contents of amylose chains and water-insoluble storage proteins, especially prolamin, increased largely under a high N level, leading to deterioration of the rice-eating quality, although a low N level (100 N kg/ha) had a less negative effect on the eating quality. Moreover, both of the indica-japonica hybrids had high ratios of inferior grains (IG), and the ratio of IG increased with the N level. Grain weight and the immature ratio of IG were reduced and increased with the N level, respectively, which are also factors for deterioration of the eating quality. The two cultivars differed greatly in the responses of eating quality to the N level, with Yongyou17 being more sensitive than Yongyou12. The current results indicated that a high N level deteriorates the eating quality of indica-japonica hybrid rice mainly due to a large increase of IG.
Highlights
Rice is a major cereal crop that provides food for nearly half of the world’s population
There was no significant difference in peak viscosity (PV), BD and SB between low nitrogen (LN) and the control (N0), while PV and BD were significantly reduced, and SB was significantly increased in both medium nitrogen (MN) and high nitrogen (HN) treatments for the two cultivars (Table 1)
In the Superior grains (SG) sample, the PV value showed the same trend with that in all grains (AG) in responding to the N level, while it was significantly increased in the inferior grains (IG) sample under LN (Figure 1A)
Summary
Rice is a major cereal crop that provides food for nearly half of the world’s population. Indica-japonica hybrid rice cultivars were widely released and planted in Southern China, which is characterized by high grain yield and relatively poor eating quality [2,3]. Reported that the protein content was a major factor affecting the rice-eating quality in a study using two indica-japonica hybrid cultivars differing in panicle types and Satake Rice Taste Analyzer (STA) [3]. The eating quality of rice is mainly controlled by genetics [1] and, affected by environmental factors, including CO2 concentration [5], temperature [6] and nitrogen rate [7,8,9], and so on. The effects of nitrogen fertilizer on the eating quality of rice was intensively investigated, but so far, the results are inconsistent and controversial
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