Development of disease-resistant, stable high-yielding, and high-quality rice variety "Yunjing-60" through double-cropping acceleration and intensive multi-environment selection in mid-altitude regions.

Developing rice varieties that combine high yield, disease resistance, grain quality, and climatic adaptability is critical for sustaining rice production, particularly under current climate change. Mid-altitude rice regions face severe challenges from rice blast, climate variability, lodging, and yield-quality trade-offs. This study integrated accelerated generation advancement with multi-environment selection to develop a high-yielding, adaptable rice variety suitable to a mid-altitude production system. Yunjing-60 is a novel rice variety developed through pedigree selection combined with double-cropping acceleration. The cross was applied between Shengnong-5 and Chujing-44. Shengnong-5 is a blast-resistant, compact architecture with medium maturity. Chujing-44 is high-yielding, lodging-tolerant, and high-quality grain. Double-cropping was applied at Yuanjiang, which is characterized by a hot and dry climate. Moreover, greenhouse cultivation was conducted during cooler months from November to February. This enabled multiple generations per year for accelerating breeding cycles. The variety comparison trial in 2022 demonstrated that Yunjing-60 surpassed the check variety Chujing-38 with superior agronomic performance. It exhibited higher effective panicle density (400.5 per m²), greater sink capacity (135 filled grains per panicle), and 8.62% higher grain yield of 13,290 kg ha⁻¹. Principal component biplot confirmed its association with key yield components. This yield advantage was supported by its ideal plant architecture and favorable growth cycle. Moreover, the variety exceeded the check variety Chujing-38 across various pathogens. It exhibited superior disease resistance with a Grade 1 rating to rice blast (index 0.80). Also, it displayed high resistance to bacterial blight, sheath blight, and rice false smut. Multi-environment selection across different altitudes accelerated trait stabilization. Regional and production trials were applied in eight diverse locations across 2023-2024. It recorded a high average yield of 10,721 kg ha⁻¹ with a yield gain of 9.8% in production trials. AMMI and GGE biplots across tested environments confirmed its superior mean yield and stability, surpassing Chujing-38. Besides, multivariate analysis using clustered heatmap visualization confirmed its consistently high-yield performance across test environments. Consistent yield across diverse ecological zones indicates its environmental adaptability and low genotype-environment interaction. Quality assessments confirmed excellent values of rice-eating compared to the national level standard. It provided a brown rice rate of 83.5%, a milled rice rate of 75.2%, and a head rice rate of 73.7%. It recorded Grade 1 transparency, 17.6% amylose content, and 70-mm gel consistency. These parameters confirm its superior milling, appearance, and eating quality. Consequently, Yunjing-60 integrated adaptive traits, accelerated breeding efficiency, and superior market value. Hence, this approach contributes to sustainable intensification, broad adaptability, and food security in subtropical highland rice systems.