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

Abstract

<p id="C2">To clarify the suitable types of rice varieties and the mechanism of high yield formation, we mainly analyzed the yield difference between<italic> indica</italic> and <italic>japonica</italic> rice in late season in the northern margin of the double-cropping rice along the Yangtze River. The experiment was conducted from 2018 to 2019 in Lujiang, Anhui province. The differences of yield and yield components, dry matter accumulation, and growth period between <italic>indica</italic> and <italic>japonica</italic> rice were compared and analyzed through 17 <italic>indica</italic> rice and 17 <italic>japonica</italic> rice varieties (strains) which were cultivated in this local area. The results showed that the overall yield level of <italic>japonical</italic> rice was similar to that of <italic>indica</italic> rice. However, compared with <italic>indica</italic> rice, the<italic> japonica</italic> rice had the characteristics of fewer yield-limiting factors, superior safety of panicle fullness, higher yield stability, and ecological safety. High-yield <italic>japonica</italic> rice mainly increased the total dry matter accumulation from transplanting to heading stage so as to improve total spikelets and yield. The effects of dry matter accumulation at different stage with different panicle types on total spikelets were quite different. Among them, the dominance period of dry matter accumulation of medium-large panicle (102.3-112.0 grains per panicle) and small panicle <italic>japonica</italic> rice (52.0-99.7 grains per panicle) are transplanting to panicle differentiation and panicle differentiation to heading stage respectively and the correlation coefficients with total spikelets were 0.709 and 0.829, respectively. Further analysis revealed that dry matter accumulation during transplanting to panicle differentiation stage of large panicle <italic>japonica</italic> rice was significantly affected by the number of tillers at tillering stage, while the dry matter accumulation during panicle differentiation to heading stage of small panicle <italic>japonica</italic> rice was affected by the number of tillers and dry weight of single stem at heading stage. In summary, this study suggested that <italic>japonica</italic> rice was a suitable late season rice variety in the northern margin area of double-cropping rice along the Yangtze River. The number of spikelets in the high-yielding <italic>japonica</italic> rice was 33.8×10³-41.0×10³ m^-2, the dry matter accumulation at maturity was 15.2-16.6 t hm^-2, and the daily yield was 58.9-64.3 kg hm^-2 d^-1. Regarding the selection of varieties, high-yield large-panicle <italic>japonica</italic> rice, such as Jia 58, Wuyujing 6571, and Changyou 5, should have strong tillering ability; while small-panicle rice varieties, such as Ningjing 7, Wuyujing 5745 and Huxiangjing 151, should have a suitable number of tillers at heading stage and dry weight of single stem. In addition, it was necessary to study the optimized cultivation techniques for high-yielding <italic>japonica</italic> rice varieties with different panicle types in order to further develop the yield potential.