Molecular Plant Breeding 2025, Vol.16, No.4, 250-260 http://genbreedpublisher.com/index.php/mpb 256 their adaptability to stress through hormone signals, such as jasmonic acid, reactive oxygen species, calcium, etc. (Finatto et al., 2015; Wang et al., 2023; Biswash et al., 2024). High temperatures can affect photosynthesis, disrupt the transport of carbon and nitrogen, shorten the grain-filling period and deteriorate the quality. The heat tolerance of different japonica rice varieties also varies (Malini et al., 2023; Li et al., 2024). However, if the roots can collaborate with beneficial bacteria, it can not only enhance the ability to resist pests and diseases and stress, but also help to better distribute nutrients and improve the efficiency of carbon and nitrogen utilization (Bandyopadhyay et al., 2022; Mani et al., 2023). 8 Case Study: Adaptability Evaluation of Three Japonica Varieties under Different Transplanting Methods 8.1 Experimental design and transplanting scenarios This case selected three typical japonica rice varieties, representing hybrid japonica rice, conventional japonica rice and soft japonica rice respectively. The experimental design includes several common transplanting methods: mechanical blanket seedling transplanting (MC), mechanical pot sports seedling wide and narrow row transplanting (K), equal row spacing mechanical transplanting (D), and mechanical direct seeding (MD). Field random block design was adopted for each variety, and indicators such as yield, quality and adaptability were recorded (Hu et al., 2020; Bian et al., 2021). 8.2 Comparative results in yield, quality, and adaptability indices Under appropriate density conditions (26.88×104 holes/hectare), wide and narrow row transplanting of pot seedlings (K) significantly increased the number of panicles and yield per unit area, which was better than equal row spacing and carpet seedling transplanting (Hu et al., 2020). Overall, mechanical transplanting (MET) has high yield and biomass, and can yield 0.6 to 3.1 tons per hectare more than manual transplanting and direct seeding (Wu et al., 2022). After reducing the density, the K method can still improve the processing quality, appearance quality and nutritional quality, but the amylose content and palatability value will decrease (Hu et al., 2020). The milled rice rate and whole milled rice rate in the MC mode are both higher than those in the MD mode, while the MD mode has better appearance quality, for example, it can reduce the chalky grain rate. Different varieties also respond differently in terms of quality. The edible taste of soft japonica rice changes the least under various transplanting methods and shows stable performance. The processing quality of conventional japonica rice is the most stable (Bian et al., 2018; Bian et al., 2021). Hybrid japonica rice has a strong nitrogen absorption capacity, a large accumulation of biomass and the most obvious increase in yield under pot seedling transplantation (Hu et al., 2018). The responses of different varieties to transplanting methods vary significantly. Soft japonica rice is not sensitive to quality changes, while conventional japonica rice shows the most obvious response to appearance changes. 8.3 Implications for cultivar-specific transplanting recommendations The results show that mechanical pot seedling wide and narrow row transplanting is particularly suitable for hybrid japonica rice and conventional japonica rice that aim for high yield and better quality. Especially after density optimization, it can take into account both output and some quality indicators (Hu et al., 2018; Hu et al., 2020). If the goal is processing quality, mechanical blanket transplanting is more suitable for conventional japonica rice. If appearance quality is emphasized, mechanical live streaming is more suitable. Soft japonica rice has strong adaptability and can adapt to various transplanting methods, and is suitable for flexible selection according to market demand (Bian et al., 2018; Bian et al., 2021). 9 Challenges and Future Perspectives 9.1 Current limitations in adaptability evaluation frameworks At present, the commonly used methods for evaluating adaptability mainly involve conducting multi-point field trials to observe the performance of varieties. However, nowadays there are more and more transplanting methods and environmental differences are also increasing. This traditional approach is no longer sufficient to comprehensively assess the true adaptability of varieties. For instance, the interaction between genotype and environment (G×E) has a significant impact on yield and quality. However, traditional methods have difficulty
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