Abstract:Rice is often exposed to cloudy and rainy weather during grain filling, resulting in decrease in rice yield and quality. By analyzing the meteorological data of rice grain filling during the last 6 years (2012-2017) in rice-growing region alongside the Yellow River (RAYR), it was found that the decrease of sunshine duration during grain filling period was the main climatic factor affecting rice production. 80 varieties of japonica rice from Japan and China were used for shading experiment, which created 65% reduction of full natural light making use of one layer of black netting and last 30 days during grain filling period. Light intensity, red light and far red light intensity, temperature and humidity in 3 weather conditions (sunny, cloudy and rainy) on the top of canopy were measured. And the 1000-grain weight, milling quality and chalkiness under shading were analyzed to screen shade tolerant japonica rice varieties. The results showed that in our study the temperature and humidity were no difference between shading and natural condition. The sunlight at the top of canopy was changed at two aspects, energy and signal, which indicated that radiation and R/FR ratio were both decreased under shading. 1000-grain weight, brown, milled and head rice rates were decreased, and chalky rice rate and chalkiness degree increased under shading. Among these characteres 1000-grain weight and chalkness were mostly affected by shading. Based on 1000-grain weight decrease, chalky grain and chalkness degree increase under shading, 4 high quality and shade tolerant japonica rice varieties were screened, which including Fangsiluo, Xinfeng5, Zhaoxiang3 and Xiaoxiang. Thus, these shade tolerant varieties with excellent grain quality served as valuable resource in future breeding for new resistant low-light varieties.