Chromosome-Level Genome Assembly of Navel orange cv. Gannanzao (Citrus sinensis Osbeck cv. Gannanzao)
The Gannanzao navel orange (Citrus sinensis Osbeck cv. Gannanzao) is a variant of the Newhall navel orange (Citrus sinensis Osbeck cv. Newhall) that exhibits an earlier maturation period, making it commercially valuable. However, the underlying mechanism behind its early maturation remains unknown. To address this, we conducted genome sequencing and de novo assembly of the Gannanzao navel orange. The assembled genome has a length of 334.57 Mb and a GC content of 31.48%. It comprises 318 contigs (N50=3.23 Mb) and 187 scaffolds (N50=31.86 Mb). Using BUSCO software, we assessed the genome's completeness, which was found to be 94.6%. The annotation revealed 23,037 gene models, 164.95 Mb of repetitive sequences, and 2,554 ncRNA. Comparative analysis identified 323 fruit ripening-related genes in the Gannanzao navel orange genome, while the Newhall navel orange genome contained 345 such genes. These genes were organized into 320 orthologous gene families, and only 30.3% of the gene families exhibited differences in gene copy numbers between the two genomes. Additionally, we identified 15 fruit ripening-related genes that have undergone adaptive evolution, suggesting their potential role in advancing fruit maturation in the Gannanzao navel orange. Our study presents the genome of the Gannanzao navel orange, serving as a valuable resource to unravel the early maturation mechanism in this variety and enriching the genetic resources available for citrus research.