Breeding and Application of Paddy-Upland Dual-adaptation Ecological Resilient Next Generation Dryland Rice Dianheyou

Purpose This study aimed to elucidate the breeding technological strategies and phenotypic plasticity of the major promoted varieties of Dianheyou series of hybrid japonica rice, to reveal their adaptive basis to diverse rice-growing ecosystems, particularly high-altitude environments, thereby providing theoretical foundations and technical pathways for breeding next generation dryland rice.

Methods The breeding process, variety characteristics, and application effects of hybrid japonica rice Dianheyou 615 and Dianheyou 918 in both paddy and upland systems (dual-niche) were systematically expounded by combining the dimensions of genetic breeding, molecular basis, ecological adaptation, physiological regulation, and agronomic phenotype.

Results By exploiting elite rice genetic resources and innovating breeding strategies and technical routes, the developed Dianheyou series of hybrid japonica rice varieties exhibited the following outstanding characteristics. 1) High phenotypic plasticity. Through the integration of indica and japonica genes and the improvement of sterile lines and restorer lines, the Dianheyou series of hybrid varieties possessed morphological and physiological adaptive plasticity that enabled them to adapt to paddy and upland cultivation as well as altitudinal variations. 2) Superior stress tolerance and disease resistance. The varieties exhibited strong topsoil emergence ability of direct seeding in dryland field, well-developed root systems, drought tolerance, and high yield maintenance under rainfed upland cultivation conditions; also demonstrated robust cold tolerance, disease resistance, and lodging resistance. 3) Broad ecological adaptability. The optimal planting altitude ranged from 800 to 1700 m, but they performed well across an altitude span of 600-2200 m, achieving a growth strategy of “shaping to the environment and adjusting to the conditions”. This had set a new record for the highest planting altitude of hybrid japonica rice. 4) Both high yield and good grain quality. In production, the field yield potential reached 7.47-12.79 t/hm² under paddy conditions and 7.01-9.99 t/hm² under upland conditions, and the grain quality met the National Grade 2 premium standard. 5) Versatile cultivation models for both paddy and upland (dual-habitat) systems. The varieties were suitable for various cultivation patterns, including both paddy and upland farming, thereby expanding the application scope of hybrid rice.

Conclusion The Dianheyou series of varieties, through the synergistic optimization of genetic improvement and environmental response mechanisms, has demonstrated outstanding phenotypic plasticity and ecological resilience. This has not only achieved a major breakthrough in high-altitude hybrid japonica rice breeding, but also provided robust varietal support and replicable technical paradigm for insuring food security and adjusting the agricultural industrial structure in plateau mountainous regions. Furthermore, it offers important insights for future crop breeding directions in the context of climate change.