Suitable varieties and high-yielding population characteristics of late season rice in the northern margin area of double-cropping rice along the Yangtze River

To study the yield difference between late-season indica and japonica rice in the northern edge of double-cropping rice along the Yangtze River, and to identify suitable varieties and high-yield formation mechanisms. The experiment was carried out in Lujiang, Anhui Province from 2018 to 2019, using 17 local conventionally planted high-quality indica and japonica varieties (line) as the research object, compare and analyze the differences in yield and composition, material accumulation and growth process of indica rice and japonica rice. The results show that the overall yield level of japonica rice and indica rice is similar, but the yield limiting factor of japonica rice is less, and the safety of full heading It has the advantages of higher yield stability and ecological security. High-yield japonica rice mainly increases the total dry matter accumulation by increasing the dry weight at the transplanting-heading stage to improve the total spikelet amount and yield. Different panicle type japonica rice varieties grow The effects of dry matter accumulation at different stages in the pre-middle stage on the total spikelets were quite different, among which the large-spike type (102.3-112.0 grains per panicle) and the small-spike type japonica (52.0-99.7 grains per panicle) had the predominant accumulation of dry matter. The correlation coefficients with the total spikelet amount reached 0.709 and 0.829 respectively. Further analysis showed that the dry matter accumulation in the transplanting-ear differentiation stage of large-spike japonica rice varieties was affected by the panicle. The number of tillers at the differentiation stage had a significant effect, while the spikelet differentiation-dry matter accumulation at the heading stage was affected by the number of tillers at the heading stage and the dry weight per stem. In conclusion, this study considered that japonica rice is the northern margin of the double-cropping rice along the river. A suitable type of double-cropping late rice in the region, high-yield japonica rice population with spikelets of 33.8×103-41.0×103 m–2, dry matter accumulation at maturity of 15.2–16.6 t hm–2, and daily yield of 58.9–64.3 kg hm–2 2 d–1. In terms of cultivar selection, high-yield and large-spike type japonica rice should have strong tillering ability, such as Jia 58, Wuyujing 6571 and Changyou 5; and small-spike type cultivars should have suitable tillering stage at heading stage. For example, Ningjing 7, Wuyujing