Rice Genomics and Genetics 2025, Vol.16, No.4, 180-198 http://cropscipublisher.com/index.php/rgg 188 performance of hybrid rice varieties is slow color change in the late stage, the leaves remain green for a long time, and sufficient source energy is provided during the filling period. "Yongyou 33" maintains beautiful leaf color before maturity, a long functional period of sword leaves, and consistent and full grain filling. The color change of the whole plant is relatively uniform, indicating that the transport of nutrients to the grains is synchronous, and no obvious premature aging occurs in the later stage. Other varieties in the "Yongyou" series also generally have green leaves under the panicle, and the mature characteristics of live stalks are obvious. Studies have shown that the leaf area index of high-yield indica-japonica hybrid rice types decays slowly after heading, and the LAI at maturity remains above 3.8, which is exactly the performance of no premature aging and continuous filling in the later stage. The experiment of Zhou et al. (2020) proved that the dry matter accumulation of high-yield hybrid rice can reach 7.9 tons/hectare in the later stage, and more than 21 tons of dry matter in the whole growth period, which is due to its delayed aging in the late growth period and maintaining strong photosynthetic production capacity. Most of the conventional rice varieties can also mature normally, but some varieties show slight signs of premature aging. For example, the tip of the leaves of "Xiushui 1717" is slightly yellowed at the maturity stage, indicating that its sword leaves are slightly aged at the end of filling. However, the overall impact on yield is not significant, because its maturity is only slightly earlier than the control by 2 days, and the grains have been fully filled. "Zhejing You 4" is an obvious early aging type, with insufficient filling stamina. Most of the leaves in the field turn yellow when mature, and the fullness of the grains is poor. Therefore, the base recommends not to promote this variety in this area. Some other hybrid rice varieties have the problem of inconsistent filling. For example, "Xiuyou 6" has been observed to have a "double filling" phenomenon, that is, some grains are filled and mature first, while the grains on the secondary branches are delayed, and the maturity is not synchronized. This may result in some grains on the same ear being ripe and some still green at harvest, which affects both yield and quality. The cause of the formation may be related to the variety's ear type and flowering habits. For this type of variety, it should be appropriately "early sowing, early planting, and sparse planting" in cultivation to extend the filling time and improve synchronization. For varieties such as "Jiafengyou 27" and "Jiafengyou 121", the base evaluated that their "color change in the mature stage is not as good as the Yongyou series", indicating that the proportion of green stems in the later stage is slightly lower than that of the "Yongyou" series. However, both of them are still within the normal maturity range, and there is no serious premature aging phenomenon, but they are slightly inferior to "Yongyou". In contrast, "Xiushui 1926" still maintains green stalks and yellow ripeness during the maturity period, and the mature phase is green and beautiful, indicating that the late assimilation products are fully transported. Most new varieties can mature with live stalks, and premature aging is not common in this demonstration, only a few varieties have a slight performance. This is related to the emphasis on late vitality in breeding in recent years. At the same time, scientific cultivation measures (such as appropriate topdressing in the later stage and foliar spraying to prevent premature aging) can also slow down leaf aging. Some high-yield varieties may have a slight lag in filling of the lower grains due to large panicles and many grains, which needs to be solved by improving variety structure or cultivation regulation. This new demonstration variety showed good synchronization and aging resistance during the filling period, and fully realized the yield potential. This is also an important physiological basis for new rice varieties to achieve stable and high yields. 5 Ecological Cultivation Techniques and Green Agricultural Practices 5.1 Substrate-based seedling raising and mechanized transplanting The demonstration base in Dahao Village, Jiashan, highlights mechanization and standardization in cultivation technology, and realizes the matching of good varieties and good methods. First, in the seedling cultivation stage, the matrix seedling stacking tray dark seedling emergence technology is adopted, that is, the seeds after soaking and germination are sown in the nutrient matrix seedling tray, stacked and shaded for 3 days to promote uniform seedlings, and then moved into the seedling field for normal management. The seedlings cultivated by this method have a well-developed root system and uniform quality, laying the foundation for machine transplanting. The seedling age is controlled at about 21 days (3 leaves and 1 heart) to ensure that the seedlings are young and vigorous when transplanted. In the planting stage, the base uniformly uses high-speed transplanters for
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