Interaction effects of mid-season hybrid rice varieties and meteorological factors on rice quality in South Sichuan winter paddy fields

In order to improve rice quality for large-scale rice production, a field experiment on mid-season hybrid rice varieties of 'ⅡY602' (high yield variety) and 'JY127' (high quality variety) was conducted in 2015-2016 under two cultivation methodsHNLD, high N and low density (pure nitrogen 210 kg·hm^-2, 90 000 points·hm^-2); LNHD:low N and high density (pure nitrogen 105 kg·hm^-2, 180 000 points·hm^-2) in 5 sowing dates (5 March, 25 March, 20 April, 4 May, 24 May). The experiment aimed at to clarify the effects of meteorological factors at different growth stages on quality of different rice varieties under different cultivation measures. The experimental results showed that with delayed seeding time, head rice rate and length to width ratio increased; chalkiness, gel consistency decreased; and chalky grain rate in "V" type changed. There were no significant difference between two cultivation methods of high N and low density and low N and high density in all rice quality indexes and no interaction effects of rice cultivation modes, variety and seeding time. There were significant interaction effects of year, seeding time and rice variety on head rice rate, chalkiness, chalky grain rate and length-to-width ratio. Significant interaction effects were also observed between year and rice varieties in gel consistency and between seeding time and rice variety in amylose content. The descending order of influence on rice quality was:variety, climate and planting mode. Meteorological conditions required to improve rice quality included small relative humidity, high daily average temperature for the period from sowing and transplanting; low average temperature, less sunshine hours from transplanting to jointing; low daily highest temperature, high daily minimum temperature and low daily average relative humidity for the period from jointing to full-heading; and less sunshine hours for the period from full-heading to mature. The meteorological factors indirectly impacted rice quality through changing grain structure before heading in hybrid rice. High temperature after grain-filling reduced rice quality. The study provided scientific basis for high-quality rice cultivation.