Effects of Shading on Grain Filling, Yield and Quality of Rice Noodle-Specific Cultivars

Low-light environments severely affect rice yield and quality. As an important raw material for rice noodles, improving rice yield and quality under low-light conditions is very important. In this study, the grain-filling dynamics, yield, processing quality, and appearance quality of two rice noodle-specific cultivars, i.e., Gui Chao II (GCII) and Guangyou 2928 (GY2928), were investigated under shading in Sichuan. At the experimental site, the soil type is loam, average temperature reaches 23.1 °C, total rainfall reaches 780–830 mm, and total sunshine duration is about 760 h. A two-factor split-plot design was conducted. Two light intensities (natural light vs. 51% shading) served as the main plot, and two rice cultivars (GCII and GY2928) served as the subplot, and each was replicated three times. Results showed that, compared with normal light, shading reduced the average filling rate (Vmean) of GCII and GY2928 by 20.67% and 18.69%, the maximum filling rate (Vmax) decreased by 20.26% and 16.18%, the 100-grain weight (Gmax) at the maximum filling rate decreased by 0.42 g and 0.21 g, and the active filling period (D) was shortened by 1.47 days and 4.01 days, respectively. Compared with normal light, the decreased grain filling led to a significant decrease in spikelet fertility by 30.62% and 28.50% for GCII and GY2928 under shading. Finally, the yield of GCII and GY2928 significantly decreased by 25.33% and 27.82% compared with normal light. Compared with normal light, shading increased the head rice rate of GCII, while that of GY2928 was significantly reduced. In contrast, the chalkiness rate and chalkiness degree of GCII under shading were significantly reduced, but those of GY2928 significantly increased. In conclusion, GCII exhibited more stable yield and quality under shading, and breeding and planting such varieties could increase rice yield and quality in low-light environments.