Objective  In this study, essential agronomical practices of the hybrid rice variety Guangyou 673 and its resistance to rice blast were analyzed to provide a scientific basis for breeding new rice varieties with improved disease-resistant and to further expand the cultivation of Guangyou 673 variety.

  Methods  Guangyou 673 was introduced for cultivation in Anxi County of Fujian Province. The impact of three essential agronomical practices, i.e., planting density (x₁), nitrogen fertilization rate (x₂) and seedling age (x₃), on the performance of Guangyou 673 was evaluated. Regression models between grain yield and the above three agronomical factors were estimated to analyze the impact of agronomical practices on grain yield. The developed functional markers of the rice blast-resistance genes Pi2, Pi9 and Pigm were used to identify the blast-resistance genes in the genetic background of Guangyou 673.

  Results  All the three studied agronomical practices revealed significant effects on grain yield of Guangyou 673. The results showed that shortening the seedling age which was with a long growth period necessitates more nitrogen fertilization to achieve higher grain yield. On the contrary, lengthening the seedling age which was with shorter growth period required less nitrogen fertilization. The maximum grain yield was achieved when planting density ranged from 2.052–2.748×10⁶ clusters per ha, N fertilizer 144.70–183.76 kg·hm⁻², and seedling age ranged from 26–33 days. Genotyping of Guangyou 673 with the functional molecular markers of Pi2, Pi9 and Pigm genes revealed that the variety Guangyou 673 contained the Pi2 blast-resistance gene.

  Conclusion  Hybrid rice variety Guangyou 673 had great characteristics of high grain yield, blast resistance and moderate growth period. The high yield more than 8 250 kg·hm⁻² could be achieved with N fertilizer 144.70–183.76 kg ·hm⁻², average plant density 2.4×10⁶ clusters per ha, and growth period 26–33 days. The results further suggested that Pi2 gene maybe the main source of blast resistance in Guangyou 673.