Molecular Plant Breeding 2025, Vol.16, No.2, 119-124 http://genbreedpublisher.com/index.php/mpb 120 However, the production management of continuous cropping of late rice also faces certain challenges. For example, the high temperature and frequent thunderstorms during the seedling raising period can easily cause the seedlings to grow too long and cause serious seedling failure after transplanting, which affects the quality of the seedlings and the occurrence of tillering; the late growth period is easily harmed by low temperatures, which affects the safe and uniform panicles and grain filling, resulting in the phenomenon of “no head growth” or “rice head warping”, which in turn affects the final yield (Cheng et al., 2018). Selecting the right rice variety is the key to ensuring stable and high yields of late rice in continuous cropping. In Rui’an City, finding varieties that are adapted to the local climate and have the advantages of stress resistance and high yield can not only improve the stability of rice production, but also optimize the grain planting structure, which is also crucial to ensuring food security. Based on this, this study conducted a comparative analysis of four common late rice varieties in continuous cropping, focusing on their key agronomic traits such as yield, panicle structure and growth period, so as to provide a scientific basis for the high-yield and high-efficiency planting of late rice in continuous cropping in Rui’an City, and also provide valuable data reference for the future selection and promotion of rice varieties. 1 Results and Analysis 1.1 Yield and yield components of tested varieties This study measured and compared the yield and key yield components of four rice varieties (Table 1). The results showed significant differences in yield among the varieties. Teyou 217 had the highest yield, reaching 550.8 kg/mu, demonstrating strong yield potential, followed by Teyou 1332 (537.9 kg/mu) and Huazheyou 261 (510.6 kg/mu). Yongyou 1540 had the lowest yield, at only 480.0 kg/mu. Table 1 Yield and panicle grain characteristics of the tested rice varieties Variety name Yield (kg/mu) Panicle grain characteristics Effective panicles (10 000/mu) Grains per panicle (grains/panicle) Thousand grain weight (g) Teyou 1332 537.9 22.75 177.9 22.7 Huazheyou 261 510.6 16.77 204.7 23.4 Yongyou 1540 480.0 15.91 207.3 23.3 Teyou217 550.8 24.85 145.9 24.7 Interestingly, Yongyou 1540 had the highest number of grains per panicle (207.3 grains/panicle) but the lowest overall yield, whereas Teyou 217 had the lowest number of grains per panicle (145.9 grains/panicle) but the highest yield. This suggests that yield is primarily influenced by the number of effective panicles. Specifically, Teyou 217’s high yield was mainly due to its high number of effective panicles (248 500 panicles/mu) and relatively high thousand-grain weight (24.7 g). Even with fewer grains per panicle, it maintained a high yield. In contrast, Teyou 1332 achieved high yield through a balance between a moderate number of effective panicles (227 500 panicles/mu) and a relatively high grain count per panicle (177.9 grains/panicle). On the other hand, Yongyou 1540, despite having the highest grain count per panicle, had the lowest number of effective panicles (159 100 panicles/mu), which likely limited its yield potential. These findings suggest that in late-season double-cropping rice cultivation, increasing the number of effective panicles may be a more effective strategy for improving yield. 1.2 Panicle grain structure of the tested varieties Rice yield is primarily determined by the number of effective panicles, the number of grains per panicle, and thousand-grain weight (Table 1). This study analyzed the panicle grain structure of the four tested varieties, and the results showed significant differences among these key yield components. In terms of effective panicle number, Teyou 217 performed the best, reaching 248 500 panicles per mu, significantly higher than the other varieties, indicating its strong tillering ability. Teyou 1332 followed closely with 227 500 panicles per mu, showing good performance as well. In contrast, Huazheyou 261 and Yongyou 1540
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